The employee appeals from the compensation judge’s finding that the October 2, 1989, work-related injury to the employee’s low back is not a substantial contributing cause of the employee’s current need for medical treatment.  We affirm.

Janet Morin, the employee, was 70 years old at the time of the hearing.  She began working for the Dresser Rand Electric Company, now known as Electric Machinery Company, Inc., the employer herein, in 1973.  The employee’s job involved applying insulation tape to coils used in power generators.  On October 2, 1989, the employee, with the assistance of a co-worker, was lifting a 100 pound coil to put it on a crane.  While lifting, she twisted her back and felt the immediate onset of low back pain.

The employee was seen by a chiropractor within a day or two of her injury.  A CT scan on October 10, 1989, showed moderate degenerative disc disease and mild degenerative facet disease at the L5-S1 level.  A November 15, 1989, MRI scan revealed moderate degenerative disc disease at L5-S1 without nerve root impingement or bony spinal stenosis, and mild tropism of the facets at L4-5 and L5-S1.

The employee was referred to the Institute for Low Back Care and began treating with Dr. Thomas Hennessey on February 23, 1990.  On examination, the doctor noted lumbar tenderness and spasm with decreased lumbar range of motion.  Dr. Hennessey diagnosed mechanical low back pain syndrome with degenerative disc and facet joint disease.  He provided conservative care with little improvement, and in October 1990, the employee elected to proceed with a surgical workup.  Facet joint blocks at L4-5 and L5-S1 provided no pain relief.  A three-level lumbar discography on August 27, 1991, reproduced the employee’s pain at L5-S1.  A post-discography CT scan showed disc degeneration with a full-thickness posterior annular tear and mild to moderate bilateral degenerative facet joint disease at L5-S1.  The L4-5 disc appeared normal with mild degenerative facet joint changes bilaterally.

The employee was seen by Dr. Richard Salib on September 11, 1991.  Based on his diagnosis of disc disruption at L5-S1, Dr. Salib recommended an anterior and posterior fusion at that level.  The surgery was performed on October 23, 1991.  At that time, the employee was noted to be moderately obese, weighing 257 pounds.  Following the surgery, the employee reported improvement with less pain, stating on December 2, 1991, that the old pain was pretty much gone.

On January 27, 1992, the employee was seen by Dr. Sunny Kim who assumed the employee’s post-surgical care.  She continued to report significant improvement compared to her pre-surgery condition.  On February 14, 1992, however, the employee reported an episode in which both her legs gave out and she fell to her knees.  After that, she stated, she had intense pain in the lumbosacral area radiating into the right buttock and leg.  A CT scan of the same date showed no evidence of postoperative complications with a solid fusion at L5-S1 and no pathologic disc protrusion or significant degenerative facet disease at the transitional L4-5 level.  On April 17, 1992, the employee told Dr. Kim she felt her symptoms were essentially the same as prior to the surgery and she did not feel she had benefited from the fusion at all.  A right lower extremity EMG on April 27, 1992, revealed no evidence of ongoing radiculopathy.

The employee continued to treat with Dr. Kim.  On August 12, 1993, a CT mylography of the lumbar spine showed a solid fusion at L5-S1 with some minor facet degeneration and asymmetry at L4-5.

The employee was last seen by Dr. Kim on April 12, 1994.  The doctor noted her back and right leg pain remained the same.  On examination, she had good range of motion without much pain and she appeared neurologically intact.

The employee participated in a physical rehabilitation program at Physician’s Neck and Back Clinic (PNBC) in April 1994.  She was diagnosed with deconditioning syndrome and mechanical spine pain post-fusion.  A follow-up report dated May 9, 1994, indicated the employee had attended six sessions and had made good objective but minimal subjective progress in rehabilitation.

The employee testified she continued to do her home exercises and attempted to self-manage her pain.  She stated she did not seek treatment unless she experienced a flare-up of her symptoms, but there was no period of time when her pain went away completely.

Approximately two years later, on April 29, 1996, the employee sought treatment at HealthPartners complaining of low back spasms with right leg pain and weakness.^[1]  Dr. Robert Titzler diagnosed known degenerative disc disease, post 1991 fusion, subacute exacerbation, and prescribed Percocet for pain.  Dr. Titzler referred the employee for an orthopedic evaluation which was performed by Dr. Holte on May 28, 1996.  The doctor noted the employee weighed 250 pounds and used a cane to ambulate.  There was palpable tenderness over the lumbosacral area, lumbar range of motion was essentially full and pain free, and she was neurologically intact.  The doctor’s impression was intermittent, chronic, recurrent lumbar sprain/strain, status post fusion, complicated by obesity.  Dr. Holte stated that what seemed to heal the employee best was rest and time, and he did not feel she had a lot of other options.  Dr. Titzler saw the employee again on August 6, 1996.  He concluded the employee had plateaued with ongoing stable chronic low back pain.

The employee returned to see Dr. Titzler on April 17, 1997, for a review and follow-up of her low back pain.  She reported the pain had started up again a few weeks ago.  Dr. Titzler prescribed Amitriptylene and Percocet as needed for severe pain.

The employee next sought treatment for her low back on August 27, 2002, approximately five years later.^[2]  Dr. Richard Wilson, at HealthPartners, noted chronic low back pain with occasional radiating pain in the right leg.^[3]  On examination, there was tenderness in the midline without muscle spasm, and no objective motor or sensory deficit.  The employee was given a one week supply of Percocet and a prescription for Amitriptylene.

In April 2003, the employee was admitted to Unity Hospital reporting progressive low back pain and right leg weakness.  A CT mylogram on April 21, 2003, showed a solid fusion at L5-S1 and degeneration of the L4-5 facet joints with moderate central canal and bilateral recess stenosis.  Dr. David Kraker performed an orthopedic evaluation while the employee was in the hospital.  He noted she was morbidly obese, weighing approximately 290 pounds.  Dr. Kraker concluded the employee’s back and leg symptoms were likely due to pathology at L4-5 and noted the employee was at risk for developing stenosis above the fusion.  The employee was also seen by Dr. Robert Jacoby for a neurologic consultation.  Dr. Jacoby stated the employee’s leg weakness seemed out of proportion for a simple radicular-type problem and out of proportion to her pain.  The employee was given an epidural steroid injection at L3-4 that resulted in only minimal improvement of her symptoms, and was discharged from the hospital on April 26, 2003.

In October 2004 and March 2005, the employee sought treatment for severe knee pain.  Reference was made to the employee’s history of back problems, but no treatment was indicated for the back.

In January 2006, the employee again sought treatment at Unity Hospital for acute low back pain extending into the right leg.  The doctor believed the flare-up represented a short-term exacerbation that would improve with time.  An updated MRI study showed a solid fusion with normal alignment at L5-S1 and mild facet and ligamentous degenerative changes at L4-5.

Following a motor vehicle accident on June 25, 2007, the employee was evaluated by Dr. James Keane at Multicare Associates.  The doctor noted a previous history of lumbar pain secondary to degenerative disc disease and a lumbar fusion some years ago.  Dr. Keane diagnosed an acute lumbar strain.  He prescribed Flexeril and advised the employee to ice her back.  She was to call back in a few days if she needed additional treatment.

The next record of treatment is dated February 19, 2010, when the employee saw Dr. Keane for low back pain.  The employee was noted to be in no acute distress, range of motion in the lumbar spine was decreased at the extremes of motion, and there was tenderness over the incision in the lower lumbar spine.  Her neurological examination was within normal limits.  She was referred to physical therapy where she was seen for three sessions.

On April 28, 2011, the employee returned to Dr. Keane reporting increasing pain in the low back radiating down the right leg.  Range of motion in the low back was decreased significantly.  The doctor diagnosed low back pain with lumbar radiculopathy and prescribed a course of prednisone and Vicodin as needed for pain.  The employee was seen on May 19, 2011, with little change in her symptoms.  A CT scan of May 24, 2011, revealed normal alignment at the L5-S1 fusion site; mild disc bulging at L4-5 with moderately severe degenerative facet changes and ligament thickening with bilateral mild to moderate spinal canal narrowing and mild neural foraminal narrowing; and slight disc bulging and mild degenerative facet changes at L3-4.

The employee continued to see Dr. Keane through 2011 and 2012, reporting persistent, worsening pain in the lower back radiating into the right leg.  The doctor primarily treated the employee with muscle relaxants and narcotic pain mediation.  In November 2011, her weight was noted to be 314 pounds.  On April 5, 2012, the employee underwent a bone density scan which showed osteoporosis in the spine.  A repeat CT scan on October 11, 2012, showed a solid fusion at L5-S1 and, at L4-5, broad-based disc bulging and severe facet degeneration bilaterally with mild spinal canal narrowing.

The employee was examined by Dr. Gary Wyard on December 19, 2012, at the request of the employer and insurer.  By report dated December 21, 2012, Dr. Wyard stated the employee’s primary complaint was low back pain with some right leg symptoms. which essentially represented her symptom complex all along, with intermittent degrees of intensity and symptoms.  On examination, the employee was 5 foot 5 inches tall and weighed 279 pounds.  She flexed forward easily.  There was generalized tenderness in the low back.  There was no spasm, sacral joint tenderness, or sensory deficit.  Muscle tone was normal.  Dr. Wyard’s impression was (1) long-standing lumbar degenerative disease, post lumbar fusion on October 23, 1991; (2) neurologically intact; and (3) obesity.  In the doctor’s opinion, the fusion, by objective standards, was successful.  Dr. Wyard agreed the employee has low back pain, but opined that her current low back pain is not causally related to her October 2, 1989, work-related injury.  The doctor explained that the employee had had subjective complaints for years with long intervals of time without treatment.  He maintained there was nothing of an objective nature on the CT scans to indicate any important findings relative to the lumber spine.  Dr. Wyard believed the employee’s complaints were out of proportion to her objective findings and that she had significant comorbidities.  Finally, Dr. Wyard concluded that the employee’s need for medical care and treatment was not related to her October 2, 1989, work injury.

On March 4, 2013, Dr. Keane provided a letter report stating that in his opinion, the work injury on October 2, 1989, was a substantial contributing factor resulting in ongoing low back pain and leg pain that was causing her current need for medical treatment.  The doctor stated the employee had significant pain, tenderness, and decreased range of motion in the low back, as well as a positive straight leg raising test of the right leg, and he believed the employee needed to see a back specialist.

The employee was seen on March 6, 2013, by Dr. Kraker for an evaluation of her back pain.  Dr. Kraker noted the employee was 70 years old with chronic back and right leg pain.  The doctor related a history of a work injury on October 2, 1989, and an anterior/posterior fusion in 1992.  He indicated the surgery helped reduce her pain for about two to three years, and that over time the employee had had flare-ups.  On examination, the employee ambulated with a normal gait, and had sensitivity over the lumbar spine from L4 to S1.  Extension was limited to 10 degrees due to pain; she had no pain with flexion.  Sensation was normal, motor strength was good, and straight leg raising was negative bilaterally.  X-rays taken that day showed spondylolisthesis at L4-5 and osteopenia.  The doctor’s diagnosis was moderate canal stenosis with spondylolisthesis and instability at L4-5.  Dr. Kraker opined the employee had developed degeneration and instability at L4-5 secondary to the fusion at L5-S1.  He believed the adjacent segment degeneration was causing the employee’s current need for medical treatment.  At a follow-up appointment on May 14, 2013, Dr. Kraker noted an epidural steroid injection at L4-5 did not provide any significant improvement.  He confirmed the April 2012 bone density scan showed osteoporosis in the spine.  He provided a referral for pool therapy, and stated that, long-term, the employee might require additional surgery.

In the fall of 2012, the employee filed Medical Requests seeking payment of various medical expenses incurred between 2000 and 2012.  In a Decision and Order, served and filed December 17, 2012, the employer and insurer were ordered to pay outstanding bills for medical treatment and care related to the employee’s low back.  On January 15, 2013, the employer and insurer filed a Request for Formal Hearing.  Following a hearing on June 5, 2013, a compensation judge at the Office of Administrative Hearings found that, while the medical care provided to the employee was reasonable and necessary, the employee failed to establish the 1989 work-related injury was a substantial contributing factor to the employee’s need for medical treatment as delineated in the outstanding medical claims.  The employee appeals.

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 (2012).  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, 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 evidence or not reasonably supported by the evidence as a whole.”  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

In making her determination, the compensation judge explicitly adopted the opinion of Dr. Wyard with respect to the issue of causation, and rejected the opinions of Dr. Keane and Dr. Kraker.  The employee argues that the evidence of record does not support the opinion of Dr. Wyard and, specifically, that seven factors listed by the compensation judge in her memorandum are are insufficient to provide a basis for Dr. Wyard’s opinion.

The employee does not argue that Dr. Wyard lacks the requisite educational and professional qualifications to render an opinion.  Rather, she asserts that Dr. Wyard did not review all of, or accurately restate, the employee’s treatment records, and that the doctor’s ultimate conclusion is inconsistent with the employee’s medicolegal history.  For example, Dr. Wyard maintained the employee had subjective complaints for years with long intervals of time without treatment.  The employee disagrees, pointing to certain details in the chronology of her medical treatment which she contends are inconsistent with Dr. Wyard’s conclusion.  While there may be some differences in the details, the medical records do reflect multiple gaps in treatment, extending from eight months to five years or so between 1994 and 2010.  Moreover, an expert need not express or even be aware of every relevant fact for his or her opinion to be valid.  See, e.g., Bossey v. Parker Hannifin, slip op. (W.C.C.A. Mar. 14, 1994).  A purported lack of information goes to the weight to be afforded the opinion.  Schulenburg v. Corn Plus, 65 W.C.D. 237, 245 (W.C.C.A. 2005).  Even where some facts may be unknown to a doctor, his opinions may still be valid, so long as the omissions do not mislead the fact finder.  Drews v. Kohl’s, 55 W.C.D. 33, 37 (W.C.C.A. 1996).  Ultimately, we are unable to say that the compensation judge was mislead by Dr. Wyard’s conclusions.

The employee argues that the seven points listed by the compensation judge in her memorandum do not provide a basis for Dr. Wyard’s opinion and his opinions should not have been adopted.  It is apparent in reading the compensation judge’s memorandum that the judge’s decision rests on her consideration of all of the medical records submitted at the hearing, in combination with Dr. Wyard’s opinion.  The judge based her determination on her conclusion that the 1991 fusion surgery provided little or no relief and that all of the scans since the surgery have demonstrated a solid fusion at L5-S1.  The judge next noted that the employee’s primary care physician, Dr. Titzler, saw the employee in 1996 and 1997 on a number of occasions, and attributed the employee’s ongoing problems to degenerative disc disease, with the employee’s weight contributing to her problem.  The judge further observed the employee had extended intervals of time without treatment for the back between 1997 and 2010, and that a bone density scan in 2007 confirmed the employee has osteoarthritis in the spine.  These findings and conclusions supplement the factual information contained in, and are not inconsistent with, the history recited and conclusions reached by Dr. Wyard.

The employee also contends the compensation judge improperly rejected the opinions of Dr. Keane and Dr. Kraker because. the judge said, they did not review all of the employee’s records and because Dr. Kraker’s history was not entirely consistent with the record.  There is no contention that the opinions of the employee’s treating physicians lack foundation.  Rather, the compensation judge found Dr. Wyard’s opinion more persuasive than Dr. Keane and Dr. Kraker with respect to the ultimate question of the causal relationship of the employee’s 1989 injury to her current need for medical treatment.  It is within the compensation judge’s discretion to assess the weight and persuasiveness of a medical expert’s opinion.  Ruether v. State, Mankato State Univ., 455 N.W.2d 475, 477, 42 W.C.D. 1118, 1121 (Minn. 1990).

Finally, the employee argues that substantial evidence does not support the conclusions of the compensation judge.  The appellant argues she did not have any symptoms of degenerative disc disease prior to the 1989 injury and that her low back has been symptomatic ever since.  The employee points out the employer and insurer accepted liability for the 1991 fusion surgery and paid permanent partial disability of 17.5%.  She contends the basis for the employer and insurer’s liability was a permanent aggravation or acceleration of her underlying or pre-existing lumbar disease.  She argues there has been no resolution of the 1989 injury, no evidence of any intervening cause, and there is nothing in the record to establish the work injury is not causally related to her current need for medical treatment.

Fundamentally, however, this case boils down to a difference in medical expert opinion regarding causation for the employee’s ongoing medical care for the low back.  Dr. Keane believed the employee’s current low back condition was the result of the “late effects” of her October 2, 1989, injury.  (Ex. B.)  Dr. Kraker opined the employee has developed adjacent segment degeneration and instability at L4-5 secondary to the work-related fusion at L5-S1.  (Ex. C.)  It was Dr. Wyard’s opinion that the employee has long-standing lumbar degenerative disc disease, post fusion, is neurologically intact, and is obese, and that her resulting low back pain is not related to her October 2, 1989, injury.  (Ex. 1.)  “[M]ore than one inference may reasonably be drawn from the evidence” in this case.  Hengemuhle, 358 N.W.2d at 60, 37 W.C.D. at 240.  It is the function of the compensation judge to resolve conflicts in expert medical testimony, and this court will usually uphold the judge’s choice of medical expert unless the facts assumed by the expert in rendering his opinion are not supported by the evidence.  See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).

It is apparent from the compensation judge’s findings and memorandum that she carefully considered the arguments of the parties, reviewed the evidence, and considered the medical experts’ opinions.  We acknowledge there is evidence that could support the employee’s contention that her work injury has remained a substantial contributing factor to her need for medical treatment.  However, the issue before this court is whether substantial evidence exists to support the compensation judge’s findings.  “Whether [this court] might have viewed the evidence differently is not the point, but whether the findings of the compensation judge are supported by evidence that a reasonable mind might accept as adequate.”  Redgate v. Sroga’s Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).  Substantial evidence in the record as a whole supports the compensation judge’s determination and we, accordingly, affirm.