The employee appeals from the compensation judge’s Findings and Order, served and filed January 12, 2012.  Because substantial evidence supports the compensation judge’s conclusions, we affirm.

The employee, Ms. Sineng Ny, came to the United States from Cambodia in 2006.  She began working at the employer herein, E.A. Sween Company, in April 2008.  The employee needed an interpreter at the hearing in the present matter.  There were interpreters present at a number of the employee’s various medical appointments as well.

The employer operated Deli Express, a business that prepares food for packaging and sale.  The employee originally worked on the day shift.  In an unappealed finding, the compensation judge confirmed that the employee had no problems doing her job on the day shift.

The employee presented to Fairview Oxboro Bloomington Urgent Care on September 27, 2009, with complaints of pain in the bilateral low back region, with radiation into the right leg.  She did not recall any injury, and her pain was exacerbated by bending or changing position.  She denied any previous history of low back problems.  On examination, the employee had a positive straight leg raise test.  She was assessed with myofascial low back strain.

The employee began working evening shifts at the employer on October 6, 2009.  The employee testified that her work on the evening shift required more lifting and faster movements.  However, the employee continued to work five days per week, eight hours per day, and she did not work on weekends.

The employee sustained a work-related injury to her low back on May 15, 2010, while in the course of her work for the employer herein, E.A. Sween Company.  The employee testified at the hearing that she noticed low back pain while pulling a cart.  According to the First Report of Injury, the employee first notified the employer of the injury on June 15, 2010, and she reported low back pain “while pulling meat supply cart.”  The employer and insurer acknowledged liability for the May 15, 2010, injury and commenced payment of benefits.

The employee’s first treatment after the work injury took place on May 27, 2010, when she presented to Allina Medical Clinic Shakopee for evaluation of back pain and to establish care.  The employee was complaining of “constant low back pain for over a year.”  She stated that her pain was worse just before her period and when she bent over.  The only reported injury history was a “motorcycle accident” she was involved in as a child.  Dr. Nancy O’Connor noted a history of back pain for more than a year.  The pain was worse if the employee lifted something heavy or did any bending.  The employee wondered if her symptoms related to an epidural while giving birth.  On examination, straight leg raise test was negative.  The employee was noted to have a tender right “SI” and mid lower lumbar.  The employee was diagnosed with lumbar pain radiating down the right leg and referred to physical therapy.

The employee had an initial physical therapy evaluation at St. Francis Regional Medical Center on June 1, 2010.  The employee was complaining of low back pain that started a year ago and had gradually gotten worse, but “the last few weekends it seems to have gotten even worse.”  The employee also said it was worse with lifting 10-pound sandwich plates.  The pain was located on the low right side and reportedly radiated “right LE to hip.”

The employee had another physical therapy session on June 3, 2010.  She reported less low back pain, but she had some pain into the right buttock and tingling into the lower extremity.  She rated her pain at 3/10, but she “did report no pain post appointment.”  On June 8, 2010, the employee told the physical therapist that she felt better.  Her pain that day was only in the middle of the spine, with some pain in the right shoulder.

The employee presented for additional physical therapy on June 10, 2010.  She reported having to leave work the day before.  She said that she feels well after her appointments and then lifts and bends at work causing more pain.  She wanted a note saying that she should lift less.  She also noted that she might be pregnant.^[1]  She reported no pain post-treatment.

On June 10, 2010, the employee also returned to see Dr. O’Connor.  The intake notes stated that the employee wanted a work note to adjust her restrictions.  She wanted to do light duty/lifting.  The employee said that she had pain in her back after therapy.  Dr. O’Connor noted that the employee’s pain was sometimes worse after physical therapy, but therapy “does seem to be helping.”  After therapy, the employee said she would feel better, but then her pain would return with work.  She was wondering about less lifting for some time to see if she could improve her strength and mechanics to be able to return to her usual work.  Dr. O’Connor issued restrictions of not lifting more than 10 pounds along with avoiding movements such as repetitive bending or bending and lifting.  The restrictions were to remain in force until July 10, 2010.  The employee was assessed with lumbar back pain that was improving with therapy.

LeAnn White, a human resources specialist with the employer, testified that the employee missed about five days of work beginning June 11, 2010.  After that, she continued working full time, with restrictions, until July 19, 2010.

Dr. O’Connor saw the employee on June 17, 2010 to fill out an FMLA form and short-term disability form.  Dr. O’Connor indicated that the employee would not be incapacitated for a single continuous period of time.  However, she might have one to three periodic flare ups per month.  The nature of the injury was described as a lumbar strain due to the employee’s work.  The injury date was listed as May 15, 2010.

The employee had her seventh physical therapy visit on June 22, 2010.  She reported feeling good after therapy.  However, she was returning to work and felt that she needed support for her back.  The employee once again reported no pain after her therapy session.

The employee continued working in a full time capacity.  She did not seek any additional medical treatment, nor did she return for physical therapy, until July 19, 2010.  The employee had the weekend off, as usual, and she did not work on July 17 and 18.

On July 19, the employee went to work at her regular evening start time but left after about half an hour.  The employee then presented to Fairview Oxboro Bloomington Urgent Care and saw Dr. Mark Nelson on July 19, 2010, at 6:30 p.m.  The employee was being seen for an evaluation of back pain.  Her pain was reportedly located in the low back, bilaterally, with no radiation.  The employee reportedly did not recall an injury history.  Dr. Nelson noted that “symptoms began day(s) ago, have been onset gradual and are stable.”  The doctor also noted a personal history of back pain as “recurrent self limited episodes of low back pain in the past.”  The employee indicated that pain was exacerbated by bending and changing positions.  On examination, Dr. Nelson noted that that employee had some limitation of motion with muscle spasm.  Her straight leg raise test was negative.  Dr. Nelson assessed the employee with back pain and sciatica.

X-rays were also taken on July 19, 2010.  The radiologist, Eric Bressler, noted, “History:  Back pain.  Sciatica.”  According to the report, the x-rays showed straightening of lumbar lordosis and congenital narrowing of the spinal canal.

The employee testified that Dr. Nelson had given her a “note to stay home,” which she had submitted to the employer.  Records show that Dr. Nelson issued a note dated July 19, 2010, which stated as follows:

There is no dispute as to whether the employee was involved with a motor vehicle accident.  However, there are numerous discrepancies in the record with regard to the date of the accident.  In fact, even at hearing, the employee initially testified on cross-examination that the accident happened on July 19, 2010, and she later stated that it happened on July 20, 2010, after additional questioning from her attorney.  The medical records contain references to both dates, and the disability case manager testified that the employee and her husband had told her the accident happened on July 19, 2010.  There are discrepancies as to the time of the accident as well.  The trial exhibits include an estimate from the motor vehicle insurer stating that the accident happened on July 20, 2010, at 7:00 a.m., but the employee testified that the accident happened at 2:40 p.m.

Regardless of the accident date, the employee returned to see Dr. O’Connor on July 22, 2010.  The intake notes indicated that the employee had an increase in pain into both lower extremities.  Dr. O’Connor noted that the employee’s symptoms were “exacerbated by work.”  The employee had not been to physical therapy since June 22, 2010, and she said it was because she had no time to go.  She had a crisis at home, and she was busy with her daughter.  Her daughter was three years old and “heavier, wants to be held.”  Dr. O’Connor did not anticipate that the employee would require permanent restrictions, but she did continue her restrictions.  Dr. O’Connor also noted that the employee had a “motor vehicle crash on 7/20/2010 after having been seen in urgent care.”  The employee was wearing a seatbelt and driving a Chevy Equinox.  She was rear-ended at a stop.  She reported “some pain at hips and arm tingling which is new.”  Dr. O’Connor noted that there may also be some whiplash.  The doctor noted that the accident happened “two days ago.”  The doctor then went on to note that the employee had “maximal pain from accident.”  Dr. O’Connor noted, “Low back pain had been present before.  Exacerbated by lifting at work.”  The employee had been advised by the physical therapist about changes in mechanics with lifting.  Dr. O’Connor noted, “Today - most pain is in low back and radiating to upper legs.”  The employee was to have additional physical therapy.

The employee returned to physical therapy on July 28, 2010.  At that time, she reported increased pain in the low back, right greater than left.  She also reported a “knife like jabbing sensation in right SI region” with burning into the buttocks and thighs, bilaterally.

On July 30, 2010, the employee saw a physician’s assistant at Dr. O’Connor’s office.  The employee reported pain in the upper right buttocks, which had started three days earlier.  The reason for the visit was listed as trauma related to a motor vehicle accident on July 19, 2010.  The employee was complaining of pain on the right side from the waist down.  She had pain radiating all the way to the calf.  The employee was also complaining of some numbness in the right leg.  The physician’s assistant noted that the employee had low back pain earlier that year, and “the pain mostly went away.”  She was still going through some workers’ compensation issues, though.^[2]  The physician’s assistant indicated that an MRI could be considered, but the employee would need to follow up with Dr. O’Connor first.  The employee was taken off work until she could see Dr. O’Connor.

The employee then remained off work for more than a month, from July 30, 2010, through September 3, 2010.

The employee returned to see Dr. O’Connor on August 5, 2010.  The intake notes stated that the employee was there for a recheck regarding a motor vehicle accident on July 20, 2010, and right hip and low back pain.  The employee said the pain was worsening and radiating down her leg.  She also had shooting pains and a constant pain level.  She hurt whether she was sitting or standing.  After her examination, Dr. O’Connor noted that the employee was complaining of right hip pain and numbness all the way down her leg, which “started after car accident and symptoms are getting worse.”  Dr. O’Connor also noted that “she is very clear that the pain going down the leg is new after MVA 7/20/2010.”  Straight leg raise test was “positive for pain in back, radiating down leg.”  Dr. O’Connor diagnosed the employee with sciatica, specifically noting that “this is new after MVA.”  An MRI was recommended, along with consideration of an epidural steroid injection.  The reason for the MRI was listed as “low back pain, recent significant trauma.”

Also on August 5, 2010, the employee underwent an MRI of the lumbar spine at St. Francis Regional Medical Center.  The MRI report noted degenerative changes at L3-4 and L4-5, which were superimposed on a congenitally narrowed spinal canal.  At L3-4, a moderate-sized right paramidline disc protrusion deformed the thecal sac, compressing the right L4 nerve root.  At L4-5, a smaller right paramidline disc protrusion caused some impingement of the right L5 nerve root as well.

The employee underwent an initial evaluation at MAPS Pain Clinic on August 17, 2010.  A questionnaire filled out that day indicated that the employee had right hip and right shoulder pain.  It also noted pain from the right hip down to the right foot.  “Motor vehicle accident” was checked as the precipitating cause for the pain.  The questionnaire states that the pain began on July 26, 2010.  In response to questions about whether the pain was work related or whether she had any prior history of similar pain, boxes were checked for “no.”  The employee then saw nurse practitioner Nancy Schmidt during her visit on August 17, 2010.  The treatment note indicates that the current problem began with the motor vehicle accident.  Leaning forward and work activity increased the pain.  The nurse practitioner noted that the MRI from St. Francis showed degenerative changes that correlated well with the employee’s pain complaints.  The employee was assessed with lumbar disc herniation and radicular pain, right greater than left, status post MVA in July 2010.  The employee received a lumbar epidural injection at MAPS on August 17, 2010, and she was instructed to remain off work until her next evaluation.

The employee saw Dr. O’Connor on August 23, 2010.  Her pain was “better” in the low back, but she still had pain in the hips and along the right side in the upper back.  The employee was no longer going to physical therapy, and Dr. O’Connor noted that “after therapy - pain had been down.”  She reviewed the MRI from August 5, 2010 as well.  Dr. O’Connor noted that “what she described is certainly consistent with possible bulge of disc - prior to MVA.  This may have exacerbated what was previously present - that had been exacerbated by the work.”  The employee was to stay off work and continue treating at MAPS.  Dr. O’Connor also noted, “While there are some additional issues from the MVA, there were clearly issues with lumbar spine from work injury and treating this well now will likely help her get back to full work without restrictions - however this may require some work conditioning physical therapy.”

The employee returned to MAPS on August 31, 2010.  She reported low back pain on both sides.  She also complained of pain radiating into the right leg.  The precipitating cause of the pain was noted to be the July 2010 motor vehicle accident, and her symptoms had been gradually increasing in episodes starting July 20, 2010.  Her pain was continuous.  The prior injection had helped with her back pain and some of her leg pain.  The employee was diagnosed with lumbar spondylosis along with degenerative disc disease and lumbar radiculopathy.  The employee was given a right SI injection.

The employee saw Robert Nicholson, M.D., in Occupational Medicine at Allina Medical Clinic Shakopee on September 2, 2010.  It was noted that the employee had been “off work due to a recent MVA.”  However, she was there for follow up regarding the May 15, 2010, work injury.  The employee was released to return to work eight hours per day, with restrictions of no lifting more than 20 pounds and restrictions on movements such as bending.  The restrictions were related to work.

On September 3, 2010, the employee returned full-time, light-duty work.

The employee returned to Allina Medical Clinic Shakopee on September 10, 2010, and she saw Dr. John Adolphson.  The intake notes indicated that the employee was there to address work restrictions, and she was experiencing more pain after returning to work full time.  The employee did not feel that she could handle eight hour shifts.  She was complaining of bilateral low back and leg pain, especially on the right.  Straight leg raise test was positive on the right.  She was given restrictions of no working more than four hours per day.

The employee also started another course of physical therapy at St. Francis on September 10, 2010.  She had been discharged earlier because she had not been back since July 28, 2010.  On September 10, she noted to have complaints of low back pain since May 15, 2010.  She also had generalized pain complaints in her neck, mid back, low back, and right leg.  She felt increased hip and low back pain with lifting at work.

The employee called Dr. O’Connor on September 21, 2010, to indicate that she could not go to work because of low back pain.  The employee went back to see Dr. O’Connor the next day, September 22, 2010.  The employee was given continued restrictions, and she was allowed to work up to six hours per day, with a requirement that she be allowed to walk periodically.  Dr. O’Connor noted that “even if there was something that happened with the motor vehicle crash, work is exacerbating the symptoms and pain from this.”

The employee presented to MAPS again on September 29, 2010.  Her chief complaint was “new-onset right hip pain.”  She was also complaining of bilateral low back pain, radiating to the right hip and to the right leg.  The treatment note once again related her pain to the motor vehicle accident.  She did not feel that the SI injection had helped manage her pain.  The low back epidural had given her better relief.

The employee and all of the other evening shift employees were laid off on October 22, 2010.  The employee was continuing to work with her restrictions, including reduced hours, at the time of the layoff.

The employee presented to MAPS again on November 9, 2010.  Her pain was “still in her low back and down the right hip and leg.”  Her pain was once again related to the motor vehicle accident.  The employee had another lumbar epidural on November 9, 2010.

The employee was seen at MAPS again on November 29, 2010.  She was referred for an EMG of the bilateral lower extremities.  The EMG was performed on December 16, 2010 and was “essentially normal.”

The employee was seen at MAPS again on December 29, 2010.  She said her pain continued to be “very bad.”  She said she would be starting a new job the next week doing “mail” at night.  The focus of the exam was on the employee’s right hip.

On December 30, 2010, the employee filed a claim petition, alleging entitlement to various benefits including temporary total disability benefits from October 22, 2010, to the present and continuing and medical benefits consequent to the work-related low back injury on May 15, 2010.  The employer and insurer admitted that the employee sustained an injury, but they argued that the injury was no longer a substantial contributing factor in the employee’s condition, and they denied the benefits as requested.

The employee had her final visit at MAPS on January 10, 2011.  She continued to complain of similar bilateral low back pain, radiating to the right leg.  Her symptoms were still being related to the motor vehicle accident.  She was referred to Dr. Kevin Mullaney for a consultation and discharged from care at MAPS.

The employee was seen in the emergency room at St. Francis on March 5, 2011.  At that time, she reported an exacerbation of chronic low back pain.  She noted, through an interpreter, that “she was involved in a motor vehicle accident in July of 2009.  Since that time, she has had problems with chronic back pain.”  She was assessed with chronic back pain related to a motor vehicle accident.

The employee saw Dr. O’Connor again on March 9, 2011.  She reported pain in the SI joint area, which was “not helped by much and worsened by activity.”

Dr. O’Connor wrote a narrative report to the employee’s attorney dated October 14, 2011.  Dr. O’Connor noted that the employee first saw her in May 2010, at which time she had pain in her low back for a year.  She had reported a “bicycle” injury as a child, and she wondered if her pain may have been related to an epidural while giving birth.  The employee also advised that her back pain was exacerbated by bending at work.  As she usually did, Dr. O’Connor had recommended that the employee undergo physical therapy.  The employee had reported that physical therapy was both causing more pain and helping as well.  When Dr. O’Connor saw the employee on July 22, 2010, she reported that it had been difficult to get to physical therapy because of a family crisis at home.  The employee had also mentioned carrying her three year old and that her legs were weakening.  In addition, the employee had reported the motor vehicle accident, which had moved her forward in her seat somewhat.  Dr. O’Connor stated, “Since then she had pain at hips (which would have been expected from contusion at seat belt contact points) as well as some tingling in her arms which may have been from being pushed forward followed by rapid extension at neck.  The low back pain had been present before the accident and exacerbated by lifting at work.”  Dr. O’Connor stated as follows:

The employee saw Dr. Kevin Mullaney at Twin Cities Spine on February 3, 2011, for an initial evaluation.  She reportedly was involved in a motor vehicle accident on July 20, 2010, which resulted in significant right-sided buttock and posterior thigh and posterolateral calf pain with standing and walking.  She had right leg pain with straight leg raising.  Dr. Mullaney reviewed the MRI and EMG, and he determined that the employee had “clear-cut stenosis of the traversing right L5 root at the L4-5 level” along with congenital stenosis.  She also had a central disc herniation without significant stenosis at L3-4.  The doctor assessed the employee with right leg pain, which appeared to be in the L5 dermatomal distribution, and significant compression of the right L5 traversing root “status post motor vehicle accident.”  He recommended a right-sided L4-5 medial facetectomy and subarticular decompression and partial discectomy.

There was no mention of the May 15, 2010, work injury in Dr. Mullaney’s treatment notes.  The employee did fill out a questionnaire at Twin Cities Spine, and it listed “spinal deformity, accident/trauma, work injury, work around the house,” and “sports/leisure” as contributing to her current spine issue.  She noted workers’ compensation issues and a pending lawsuit.  She also noted that she was “self-employed” and that she had been for two and a half years.  The employee signed an insurance form that indicated that her injury was related to the auto accident and listed the auto insurer for coverage.

The employee saw Dr. Mullaney on June 30, 2011.  She had significant dysfunction in her right and left legs.  The doctor noted that she also had “known congenital with overlying disc herniation and stenosis at L3-4 and L4-5 levels.”  Dr. Mullaney recommended bilateral L3-4 and L4-5 hemilaminotomy, facetectomy, and subarticular decompression.

The employer and insurer sent the employee for two independent medical examinations with Dr. Robert Barnett, which took place in November 2010 and June 2011.

After the first examination, Dr. Barnett issued a report dated November 29, 2010.  According to that report, the employee described working in a position that required her to bend forward, reach, pull, and twist to the side.  As a result, she developed the onset of low back pain with numbness and pain extending into the right leg in May 2010.  Dr. Barnett then noted that the employee was involved in motor vehicle accident on July 19, 2010.  The employee reportedly told Dr. Barnett that her symptoms continued after the May 2010 injury date, and the motor vehicle accident aggravated her situation with increasing back pain and increasing leg pain.  Dr. Barnett opined that the employee sustained an injury to her lumbar spine as a result of her work activities on or around May 15, 2010.  However, he noted that “without actual review of the MRI scan of the lumbar spine, I cannot state with a reasonable degree of medical certainty that the work activities on or about May 15, 2010, are a substantial contributing factor to the current lumbar spine condition.”  Dr. Barnett noted that he did not have complete medical records, including the MRI scan itself.  The records from MAPS suggested that the employee’s symptoms followed the motor vehicle accident, but other records and the employee’s own description suggested that the symptoms predated the accident.  Dr. Barnett also noted that the employee “had a pre-existing degenerative condition in the lumbar spine prior to the May 15, 2010, injury.”  Then, she had the motor vehicle accident, which represented “a symptomatic aggravation of the lumbar spine condition, which predated the automobile accident.”

After the second independent medical examination, Dr. Barnett issued a report dated July 26, 2011.  He stated as follows:

Dr. Barnett also gave a deposition shortly before the hearing.  He summarized his ultimate opinion at his deposition, explaining that the employee had preexisting degenerative disc disease before the May 15, 2010, work injury, without anatomic changes.  The employee’s symptoms at that time, as evidenced in the July 19, 2010, treatment note, were self-limited and stable.  Dr. Barnett opined that the employee’s symptoms would have resolved as a temporary aggravation of the preexisting condition.  The motor vehicle accident then was the sole cause of the anatomic changes in the employee’s spine after that accident.

The auto insurer sent the employee for an independent medical examination with Dr. Ansar Ahmed in March 2011.  The employee reportedly had “complaints of low back pain, right hip pain, and right knee pain since her accident in July of 2010.”  The employee reported “that she had back pain in the past, but denies any previous motor vehicle accident, work, or recreational injuries.”  Dr. Ahmed noted that the employee’s prior medical history was “notable” for prior complaints of low back pain dating back to 2009.  He opined that the motor vehicle accident was “minor” and that the employee’s low back problems, including disc protrusions, were related to a preexisting condition.  Specifically, Dr. Ahmed stated:

The case came on for hearing, and the employee argued that the motor vehicle accident was a minor incident and that the May 15, 2010, work injury continued to be a substantial contributing factor in her disability and need for medical treatment, including the surgical recommendation.  The compensation judge, however, concluded that the employee did not establish that her May 15, 2010, injury was a substantial contributing factor in her disability and need for medical treatment, as claimed.  The compensation judge also went on to conclude that the motor vehicle accident was a superseding, intervening cause of the employee’s subsequent disability and need for medical treatment.  The employee appeals.

In reviewing cases on appeal, the Workers’ Compensation Court of Appeals must determine whether “the findings of fact and order [are] clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted.”  Minn. Stat. § 176.421, subd. 1.  Substantial evidence supports the findings if, in the context of the entire record, “they are supported by evidence that a reasonable mind might accept as adequate.”  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).  Where evidence conflicts or more than one inference may reasonably be drawn from the evidence, the findings are to be affirmed.  Id. at 60, 37 W.C.D. at 240.  Similarly, “[f]actfindings are clearly erroneous only if the reviewing court on the entire evidence is left with a definite and firm conviction that a mistake has been committed.”  Northern States Power Co. v. Lyon Foods Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).  Findings of fact should not be disturbed, even though the reviewing court might disagree with them, “unless they are clearly erroneous in the sense that they are manifestly contrary to the weight of the evidence or not reasonably supported by the evidence as a whole.”  Id.

As indicated in her memorandum, the compensation judge concluded that the employee sustained a temporary aggravation as a result of the May 15, 2010, work injury.  As such, she concluded that the employee failed to meet her burden of proof to show that the work injury continued to be a substantial contributing factor in her disability and need for medical treatment, especially after the motor vehicle accident.  The compensation judge further concluded that the motor vehicle accident was a superseding, intervening incident.

The employee argues that both the work injury and the motor vehicle accident could be deemed to be substantial contributing factors in the employee’s claimed disability and need for medical treatment, including the recommended surgery.  Therefore, she argues that it was error for the compensation judge to deny her benefits as claimed.^[3]

As a general rule, the work injury need not be the sole cause of the employee’s disability or need for medical treatment, and disability or medical expenses incurred as a result of an aggravation of a work injury continue to be the responsibility of the employer if the work injury remains a substantial contributing factor in the need for treatment.  See Roman v. Minneapolis St. Ry. Co., 268 Minn. 367, 129 N.W.2d 550, 23 W.C.D. 573 (1974).  See also Smith v. Timberland, No. WC06-106 (W.C.C.A. Aug. 23, 2006) (citing Michlitsch v. Michlitsch Builders, Inc., No. WC06-116 (W.C.C.A. Aug. 10, 2006); Andeen v. Emmaus Nursing Home, 256 N.W.2d 290, 30 W.C.D. 269 (Minn. 1977); Rohr v. Knutson Constr. Co., 232 N.W.2d 233, 28 W.C.D. 23 (Minn. 1975)).  “The causal relationship with a work injury may be broken by a superseding, intervening cause of the aggravation.”  Smith, No. WC06-106.  However, when the work injury remains a substantial contributing factor in the employee’s disability or need for medical treatment, the non-work injury or condition is not a superseding, intervening cause.  Hamm v. Marvin Windows & Doors, 64 W.C.D. 270, 280 (W.C.C.A. 2004), summarily aff’d (Minn. July 20, 2004).

The employee argues that the compensation judge applied an incorrect legal standard in determining that the employee’s May 15, 2010, injury was no longer a substantial contributing factor in her ongoing medical condition and issues after the motor vehicle accident.  As indicated in Buford v. Ford Motor Co., 52 W.C.D. 723, 727-28 (W.C.C.A. 1995), the proper test in a superseding, intervening cause case is essentially a “substantial contributing cause” test.  The compensation judge cited the case of Turney v. Ebenezer Soc’y, 39 W.C.D. 809, 818 (W.C.C.A. 1986), summarily aff’d (Minn. Apr. 9, 1987), which states that it is only necessary for a work injury to be a substantial contributing cause in order to impose continued liability on an employer and insurer, even after an intervening incident.  The compensation judge noted that “it was only necessary to have the work injury be a substantial contributing cause to the ongoing disability in order for the ongoing liability of the workers’ compensation insurer to continue following the intervening non-work related accident.”  Further, the compensation judge stated that “the question is whether or not [the May 15, 2010] injury continued to be a significant contributing factor to the employee’s ongoing medical condition.”  Therefore, we are persuaded that the compensation judge applied the correct legal standard in reaching her conclusions regarding whether the employee’s work injury remained a substantial contributing factor in her ongoing medical condition.

The employee argues that the employee’s accident, in these circumstances, does not constitute the type of superseding, intervening cause that traditionally has been defined by the case law as an aggravation that is “the result of conduct by the employee which is unreasonable, negligent, dangerous or abnormal.”  As this court noted in Buford, cases on superseding, intervening cause can be divided into two general categories.  52 W.C.D. at 728 n.3.  The first is where the employee’s own actions result in additional disability,^[4] and the second is where the additional disability stems from some unrelated trauma or disease.^[5]  In the first category, the aggravation must be the result of conduct by the employee which is unreasonable, negligent, dangerous, or abnormal.  See Eide v. Whirlpool Seeger Corp., 260 Minn. 98, 109 N.W.2d 47, 21 W.C.D. 437 (1961).  In the second category, the medical evidence must show that a causal relationship remains between the work injury and the employee’s current condition.  Smith, No. WC06-106.  Here, we agree that the employee’s motor vehicle accident was not of the type contemplated by Eide and similar cases involving “unreasonable, negligent, dangerous or abnormal” activity.  Id.  However, that does not mandate a finding that the employee’s work injury remains a substantial contributing factor, unless the medical evidence shows that such a causal relationship exists.  Id.

Ultimately, the determination of whether a subsequent incident or event is a superseding, intervening cause of disability or need for medical treatment is a question of fact for the compensation judge, and the employer and insurer have the burden of proof.  See Rohr, 232 N.W.2d at 235, 28 W.C.D. at 25; Trettel v. Cambridge Reg’l Ctr., slip op. (W.C.C.A. Dec. 17, 2003).  In other words, whether a causal relationship exists is a fact finding by the judge, and if there is medical support for a judge’s finding on that issue, this court must affirm.  Smith, No. WC06-106 (citing Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 37 W.C.D. 235 (Minn. 1984)).^[6]

The issue in intervening cause cases is not merely whether the intervening injury or condition is itself a substantial contributing cause of the employee’s subsequent disability but whether that intervening injury or condition has broken the causal connection between the employee’s work injury and that disability.  Smith, No. WC06-106; Hamm, 64 W.C.D. at 280 (discussing Buford).  Here, the employee argues that there is substantial evidence to show that the May 15, 2010, injury remained a substantial contributing factor in the employee’s condition and claimed disability and need for medical treatment, even after the motor vehicle accident in July 2012.  Even if that is true, on appeal, the point is not whether this court might have viewed the evidence differently, but whether the findings of the compensation judge are supported by evidence that a reasonable mind might accept as adequate.  See Redgate v. Sroga’s Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).

This may well be a close case factually.  However, that is the difficulty with superseding, intervening cause cases.  What constitutes a “substantial” or “significant” contributing factor in a workers’ compensation setting can not been precisely defined since each case stands on its own facts.  As this court stated in Hamm:

Here, the compensation judge relied, primarily, on Dr. Barnett’s opinions in finding that the work injury was a temporary aggravation of a preexisting condition.  The employee argues that Dr. Barnett’s opinions lack foundation, or should, at least, be closely scrutinized.  Dr. Barnett obtained a history from the employee, reviewed her medical records, including the MRI report, and conducted multiple physical examinations of the employee.  As a general rule, this combination of medical expertise and practical experience is sufficient foundation to establish competency to provide an expert medical opinion.  See Grunst v. Immanuel-St. Joseph Hosp., 424 N.W.2d 66, 40 W.C.D. 1130 (Minn. 1988).

The employee argues, however, that Dr. Barnett’s second IME report is inconsistent with his initial report.  The employee argues that Dr. Barnett’s opinions are “contradictory” because he concluded in his first IME report that the motor vehicle accident was merely a temporary aggravation of a preexisting condition.  Therefore, she argues that it cannot support a finding of superseding, intervening cause, especially when compared with Dr. Barnett’s first IME report and the opinions of Dr. O’Connor and Dr. Ahmed.

In his first report, Dr. Barnett made it clear that he felt the employee’s May 15, 2010, injury was a symptomatic aggravation of a preexisting low back condition.  He then stated that he could not say for sure whether the motor vehicle accident was an aggravation of the preexisting condition without reviewing the MRI.  The employee argues that because Dr. Barnett never actually reviewed the MRI scan itself, his subsequent conclusions lack foundation.  However, as Dr. Barnett later explained at his deposition, the MRI was done after the accident, and even if he reviewed the MRI, he would not be able to say whether the findings existed before or after the accident.  Dr. O’Connor noted that same problem in her October 14, 2011, report.  Although Dr. Ahmed “incorporated the results” of the MRI into his report, as argued by the employee in her brief, there is no indication that Dr. Ahmed reviewed the actual MRI scan either. In fact, the language Dr. Ahmed uses in his discussion of the MRI results closely mirrors that of the MRI report.  Thus, the fact that Dr. Barnett did not review the MRI does not mean that his subsequent opinions lacked foundation.

In his second IME report, Dr. Barnett opined that the May 15, 2010, work injury was “a temporary symptomatic aggravation of preexisting condition” and that the “motor vehicle accident appears to be a substantial contributing factor to further medical evaluation and treatment in the form of increased acuity in the back pain and increased intensity of the radicular symptoms requiring a heightened level of evaluation and treatment.”  As such, Dr. Barnett noted, “It is my opinion that medical evaluation and treatment taking place after July 20, 2010 should be considered on the basis of the motor vehicle accident being substantial contributing cause to the lumbar spine condition occurring as a consequence of the motor vehicle accident.”

At his deposition, Dr. Barnett stated that before the motor vehicle accident, the employee had a history of self-limited back pain.  The employee did not have any consistent “demonstrable objective evidence” of lumbar radiculitis before the motor vehicle accident.  Dr. Barnett opined that the work injury was, if anything, a symptomatic aggravation of the employee’s low back condition that was evidenced as early as the September 27, 2009, visit.  Had it not been for the motor vehicle accident, the employee would have had, if anything, self-limited episodic low back pain episodes with occasional radiation into the leg and inconsistent findings on examination.  As Dr. Barnett explained, even by the time of the July 19, 2010, visit, Dr. Nelson noted that the employee’s condition had stabilized, and there were no neurological findings on examination, including the straight leg raise test.  It was only after the accident that the employee had consistent neurological findings, and her treatment was escalated, including an MRI, EMG, injections, and the eventual surgical recommendation.  Therefore, Dr. Barnett opined that the records showed anatomic changes in the employee’s spine after the motor vehicle accident, which had not been present before the accident.

The employee relies primarily on Dr. O’Connor’s records for her argument that the work injury remained a substantial contributing factor.  Dr. O’Connor frequently reported that the employee’s work activities at the employer “exacerbated” her problems.  However, the records show that almost any activity, whether work related or not, was “exacerbating” the employee’s symptoms and complaints both before and after the motor vehicle accident.  The issue in this case is one of causation.  As she stated in her October 14, 2011, report, Dr. O’Connor could not definitively conclude that the employee’s work injury remained a substantial contributing factor in her condition, disability, or need for treatment.

Furthermore, as of June 17, 2010, when she filled out the FMLA and short-term disability paperwork for the employee, Dr. O’Connor was assessing her with a low back strain, which would not cause her to be incapacitated for a single continuous period of time, with potential for periodic flare ups.  On August 5, 2010, Dr. O’Connor noted that the employee was complaining of right hip pain and numbness all the way down her leg, which “started after car accident and symptoms are getting worse.”  The doctor also noted that “she is very clear that the pain going down the leg is new after MVA 7/20/2010.”  Straight leg raise test was positive for pain in the back radiating down the leg.  Dr. O’Connor diagnosed the employee with sciatica, specifically noting that “this is new after MVA.”  As Dr. Barnett pointed out, it was only after the motor vehicle accident that Dr. O’Connor recommended additional treatment such as the MRI.  The employee went on to have an EMG, injections at MAPS, and Dr. Mullaney eventually made the surgical recommendation.  None of these treatments were even discussed before the motor vehicle accident.^[7]

The other medical records also provide support for the compensation judge’s conclusion that the employee’s work injury was no longer a substantial contributing factor after the motor vehicle accident.  As early as September 27, 2009, the employee was complaining of bilateral low back pain radiating into the right leg, with a positive straight leg raise test on exam.

Dr. Mullaney and the employee’s physicians at MAPS repeatedly related the employee’s ongoing issues to her motor vehicle accident and not to her work injury.  The employee testified at hearing that there were issues with the interpreters at both MAPS and Twin Cities Spine Center, which explain the fact that the physicians at those facilities relate the employee’s ongoing issues to the motor vehicle accident and not to the work injury.  The compensation judge considered this argument and pointed out that there are a number of “discrepancies” throughout the medical records regarding the employee’s symptoms and history.  “Assessment of witness credibility is the unique function of the factfinder.”  Tews v. George A. Hormel & Co., 430 N.W.2d 178, 180, 41 W.C.D. 410, 412 (Minn. 1988).  It is not this court’s function to evaluate the credibility and probative value of witness testimony and to choose different inferences from the evidence than the compensation judge.  Krotzer v. Browning-Ferris/Woodlake Sanitation Serv., 459 N.W.2d 509, 512-13, 43 W.C.D. 254, 260-61 (Minn. 1990).^[8]  Ultimately, the compensation judge did not accept the employee’s argument that interpreter issues accounted for all of the inconsistencies involved here.

Although Dr. Ahmed did not feel the employee’s ongoing issues were related to her motor vehicle accident, he did not specifically relate the employee’s symptoms to her work injury.  He related the ongoing issues to a preexisting condition that was present before the motor vehicle accident, but even Dr. Ahmed did not specifically relate the employee’s ongoing issues to her work injury.

The employee relies on the cases of Hamm, Buford, and Keane v. Critical Care Servs., Inc., No. WC11-5343 (W.C.C.A. Mar. 5, 2012),^[9] to argue that her work injury continued to be a substantial contributing cause of her disability and need for medical treatment.  Those cases, however, all involved underlying work injuries that were much more permanent in nature than the employee’s May 15, 2010, injury.  For example, in Hamm, the employee had already received an award of permanent partial disability benefits, and he had ongoing, permanent restrictions following the work injury.  The case also involved a permanent total disability claim.  In Buford, the employee had multiple prior injuries to multiple body parts, and he was essentially restricted to sedentary work.  In fact, as indicated in a concurring opinion, the evidence in Buford may have been sufficient to show that the employee was permanently and totally disabled before the intervening accident.  In Keane, the employee had already undergone a disc replacement surgery at the same level that was injured in the subsequent motor vehicle accident.

As the Minnesota Supreme Court explained:

In this case, the compensation judge adopted Dr. Barnett’s opinions over the other experts involved.  There is support for the compensation judge’s conclusion that the employee’s work injury was a temporary aggravation of a preexisting condition and that the employee had not sustained a “permanently weakened physical condition” because of that injury.  As in Hamm, Buford, and Keane, the compensation judge’s determination must be affirmed on the basis of the substantial evidence in support thereof.

The employee argues that she had an “established history of increasing low back pain” as of July 19, 2010.  We disagree.  The July 19, 2010, record actually seems to indicate that her symptoms were “stable” at that point, and there was no indication in the treatment note that the employee was relating her symptoms to her work activities.  She had not been in for treatment since her last physical therapy appointment on June 22, 2010, and she had continued working until the weekend of July 17 and 18, when she was off as scheduled.  When the employee was seen again on July 19, 2010, she reported pain in the low back, bilaterally, with no radiation.  Dr. Nelson also noted that on examination, straight leg raise test was negative.  This finding is obviously contrary to Dr. O’Connor’s finding on August 5, 2010.

The employee further argues that because Dr. Barnett opines that the employee’s symptoms from before the motor vehicle accident were intermittent and activity related, and because Dr. Barnett opined that the employee’s symptoms increased significantly after the accident, the work injury necessarily remained a substantial contributing factor after the injury.  As such, the employee argues that the employer and insurer could not show that the motor vehicle accident was the sole cause of the employee’s ongoing disability and need for medical treatment.  However, even if the employee had ongoing symptoms that were arguably attributable to her work injury at the time of her motor vehicle accident, a dramatic increase in the nature and severity of symptoms as a result of a non-work injury is evidence of a superseding, intervening cause.  Jackson, slip op. (citing Kaufhold v. Auburn Manor, slip op. (W.C.C.A. Aug. 27, 1993); Hendrickson v. Potlatch Corp., 43 W.C.D. 212 (1990), summarily aff’d (Minn. July 31, 1990)).

The Jackson case is very similar to the circumstances here, and it is instructive.  In Jackson, the employee sustained work injuries in early 1992.  The injuries involved multiple body parts, including his low back with symptoms radiating into his left leg, and he was diagnosed at one point with low back pain and left sciatica.  The employee was taken off work because of the work injuries on August 5, 1992.  By early September 1992, the employee was continuing to experience persistent, sharp low back pain, but his leg symptoms had improved.  On September 24, 1992, the employee’s treating physician felt that he had “stabilized,” and the employee was released to return to full-time work with restrictions, including lifting no more than ten pounds.

Just four days later, however, the employee was involved in a non-work related automobile accident when he was rear ended while stopped at a traffic light.  Following the accident, the employee experienced constant, sharp low back pain that radiated into his left buttock down his leg into his foot.  The employee’s treating physician opined that the employee’s condition after the motor vehicle accident was solely the result of that accident, and the employee was taken off work because of the accident.

The compensation judge reviewed conflicting medical opinions, including an IME that apportioned liability for ongoing symptoms between both the work injury and the motor vehicle accident.  The employee testified and the medical records also showed that his low back diagnosis did not change after the accident, but the symptoms increased in severity.  As such, the employee argued that his work injury remained a substantial contributing factor in his ongoing condition.  The compensation judge, however, concluded that the employee did not sustain his burden of proof that the work injury was a substantial contributing cause of his disability and need for medical care after the motor vehicle accident.  The compensation judge also found that the employee’s September 1992 automobile accident was a superseding, intervening cause of the subsequent disability and need for chiropractic care.

This court found that substantial evidence supported the compensation judge’s conclusion and affirmed.  Specifically, this court noted that the severity and nature of the employee’s symptoms dramatically changed after the accident, the employee was released to return to full-time work prior to the accident, although with restrictions, and the employee was unable to work for a significant period of time following the accident.  See also Austin v. Coca-Cola Bottling Midwest, slip op. (W.C.C.A. Aug. 6, 1991) (holding that where the employee’s symptoms had stabilized, and he had “returned to an almost normal level of function,” a subsequent motor vehicle accident involving injuries to the same body parts was a superseding, intervening cause of the employee’s disability).

As in Jackson, the employee here argues that because her symptoms before and after the motor vehicle accident involved her low back and her right leg, the work injury remained a substantial contributing factor after the motor vehicle accident.  The employee points to numerous references in the medical records that she believes mandate a finding that the employee’s work injury continued to remain a substantial contributing factor in her issues after the motor vehicle accident.  For example, she argues that even Dr. Barnett conceded that there was a potential diagnosis of sciatica before the motor vehicle accident, and that she was diagnosed with sciatica at the time of the July 19, 2010, visit.

However, as indicated in Jackson, prior complaints of low back and leg symptoms, and even a possible diagnosis of sciatica, are not enough to mandate a conclusion that the work injury remained a substantial contributing factor in the employee’s condition.  Unless the medical evidence establishes that a causal relationship still exists between the employee’s work injury and her ongoing condition after the accident, the employer and insurer are not responsible for the employee’s ongoing disability and medical expenses, and this is a factual question for the compensation judge.  Smith, No. WC06-106.

Here, the compensation judge considered all of the evidence presented, including the employee’s testimony and the medical opinions offered from Dr. Barnett, Dr. O’Connor, and Dr. Ahmed.  The experts involved here disagreed regarding the underlying causation of the employee’s ongoing complaints and the cause of her disability and need for treatment.  The compensation judge correctly stated in her memorandum that “While [the employee] had difficulty doing her work, the medical opinions do not conclude that the work injury continued to be the reason for that difficulty, as opposed to the motor vehicle accident.”  In cases such as this one, which involve a pattern of prior symptoms and a possible temporary aggravation, it is sometimes difficult to determine where the symptoms attributable to the aggravation might end.  Thus, as indicated in cases such as Hamm and Flowers, it is difficult to establish an exact line as to when a work injury is no longer a substantial contributing factor in ongoing disability or need for medical treatment.  The compensation judge could reasonably rely on the opinion of Dr. Barnett, as opposed to that of Dr. Ahmed or Dr. O’Connor, when reaching her conclusion that the work injury was a temporary aggravation that was no longer a substantial contributing cause of the employee’s ongoing medical condition and claimed disability and need for medical treatment after the motor vehicle accident.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985) (resolution of conflicting expert medical testimony is function of trier of fact and will usually be upheld on appeal).  Because there is substantial evidence to support the compensation judge’s conclusion that the employee sustained a temporary aggravation of a preexisting condition as a result of her work injury and that after the motor vehicle accident, the work injury was no longer a substantial contributing factor in the employee’s disability and need for medical treatment, we affirm.