The employee appeals from the finding that she failed to prove that her 1996 work injury was a substantial contributing cause of her disabling low back condition and related 2008 surgery.  We affirm.

The employee, Laurie K. Getman, began treating at the Park Nicollet Clinic in April, 1996.  Records beginning in that month indicate a past medical history of migraine headaches and associated right arm numbness and tingling since 1993.  The employee also has a longstanding diagnosis of osteoarthritis and rheumatoid arthritis for which she has been on medications since 1991.  She testified that the rheumatoid arthritis has caused pain and swelling in her joints, primarily in her hands and feet.  The osteoarthritis is a degenerative condition that causes pain in her knees.  The employee has also trochanter bursitis which sometimes has caused intermittent pain in her right hip.

On October 16, 1996, the employee sustained an admitted work injury while working for the employer, the Carlson Marketing Group, as a benefits specialist in the employer’s human resources department.  The injury occurred when she was in a stockroom moving some boxes of forms and brochures, weighing about 15-20 pounds.  The employee testified that she lost her footing and wrenched her neck and back, experiencing an immediate pain in her neck down her spine and legs.  She also testified that she sought treatment that day in the urgent care department at the Park Nicollet Clinic.  No medical records have been found showing that visit or any treatment on that date; according to the employee’s testimony, her physicians thought she might have pulled some muscles, and Flexeril and Advil were prescribed.  The employee was able to return to work without lost time.  She was able to continue working at her usual job duties, although she testified that she needed to change some of her activities following the injury as a result of ongoing neck, back and leg pain.

The employee did not return to the Park Nicollet Clinic for further treatment until April 3, 1997, when she was seen for right hand pain secondary to keyboarding.  The employee was diagnosed with right hand tendinitis.  Her symptoms continued despite work restrictions and conservative treatment and she began complaining of pain through the right arm as well as in the thoracic region.  She was subsequently seen by multiple physicians at the Park Nicollet Clinic for her neck and right arm symptoms. The employee’s upper extremity complaints were treated with physical therapy, and the employee also received a prescription for a TENS unit.  The employee testified that she also, on her own, used the TENS unit for low back pain.

An MRI scan of the employee’s neck, performed on September 8, 1997, revealed disc herniations at the C4-5 and C5-6 levels with flattening of the cervical cord.  On that date, the employee met with an internal medicine specialist to discuss the scan findings.  The employee complained of a recurrent problem with right arm pain since March, and reported recently having shooting pains from her neck into her shoulder.  She also reported some numbness and discomfort in the lower extremities, particularly the right leg.  She could not recall having undergone any major physical trauma, except for an incident at work in October, 1996, when she “stood up at work and she did strike her back, as well as the back of her head on a cabinet” which “sent shock waves down into her spine and arms, and she now recalls this injury.”  This is the first medical record in evidence making reference to symptoms involving the low back or lower extremities.

The employee was referred to Dr. Cox, a neurosurgeon, for evaluation of right-sided shoulder and arm pain.  Dr. Cox saw the employee on September 11, 1997 and recommended a trial of prolotherapy for the employee’s chronic cervical pain.

In November 1997, the employee noted left hip pain in addition to her leg numbness.  In a chart note dated December 1, 1997, Dr. Mary Ryken, who was treating the employee in prolotherapy, noted a diagnostic impression of a chronic low back pain with spondylosis, deconditioning, obesity, and lumbar sprain/strain.  She provided the employee with a lumbosacral support and referred her for physical therapy.  The employee also had prolotherapy for the neck and right shoulder and acupuncture for the hip and low back.  She completed nine or ten prolotherapy sessions over the course of one month but noted no decrease in symptoms.

The employee next saw Dr. Ryken on January 7, 1998.  She was experiencing mid lumbar and bilateral posterior hip pain.  Dr. Ryken diagnosed chronic cervical, thoracic, and lumbar pain with myofascial findings and multiple level cervical disc herniations.  The employee continued to receive prolotherapy treatments during the spring and early summer of 1998.  In a follow up appointment with Dr. Ryken on July 22, 1998, the employee reported a 50% improvement of her condition following prolotherapy, with most of her pain localized to the neck and shoulder.  Twenty percent of her pain was in the medial right buttock, although the buttock pain was intermittent.

The employee continued to receive conservative treatment for her neck and low back over the next several years with no significant increase or decrease in symptoms except for an occasional flare up of symptoms.  She continued at her job with the employer and missed no time from work.

On October 9, 2002, the employee experienced a sudden onset of severe pain in her low back and into her right leg, lateral foot and ankle while walking to her car.  On October 11, 2002, she was evaluated by Dr. Edward Rydell for an acute onset of posterior right hip pain.  The pain was noted to be constant and radiating down the right leg to the foot and she complained of paresthesias in the lateral aspect of the right thigh and lower leg.  Tenderness was present over the right sacroiliac joint, as well as over the right mid buttock.  There was alteration of sensation in the lateral aspect of the employee’s right lower extremity.  She was diagnosed with possible right piriformis muscle spasm or right sacroiliac dysfunction.

On October 30, 2002, the employee underwent an MRI of the lumbar spine.  The scan revealed a disc herniation without nerve root compression at L5-S1 and a mild disc bulge with mild central canal narrowing at L4-5.

On November 4, 2002, Ms. Getman was evaluated by an occupational medicine specialist, Dr. Anne Brutlag.  Dr. Brutlag diagnosed discogenic low back pain with spasm or lateral shift.  The employee gave as history that her low back pain was of approximately one month’s duration, with a sudden onset of symptoms on October 9, 2002 while walking.  Straight leg raising test was positive on the right.  Dr. Brutlag recommended hospitalization for pain control and further evaluation.

The employee was evaluated by Dr. Andrew J. Smith, a neurosurgeon, on November 4, 2002.  The employee again noted that her pain had started in October, 2002 while walking and the doctor noted that “she denies any more severe injuries than just that walking incident.”  The employee’s pain had moved into both legs, and was now worse on the left than the right.  Dr. Smith found clinical indications of bilateral sensory L5 radiculopathy, with numbness in the L5 distribution bilaterally and a positive Patrick's test with external rotation of both hips.  He discharged her with medications.  On November 6, 2002, Ms. Getman underwent an epidural steroid and anesthetic injection at the left L5-S1 level.

The employee was seen by Dr. Brutlag on November 14, 2002.  Her symptoms had not changed significantly and she complained of difficulty sitting at work, which increased her symptoms.  Dr. Brutlag recommended that she continue using OxyContin, Vicodin, Flexeril and a TENS unit.

Medical records over the next several months show a continuing improvement in the employee’s low back and leg pain.  Her diagnosis was discogenic low back pain with a herniated disc and rheumatoid arthritis.

In September, 2003, the employee complained of a flare-up of her pain, primarily in her neck, shoulder, and upper back, with secondary low back pain. When seen by Dr. Brutlag on December 9, 2003, the employee did not mention low back symptoms.

The employee continued to work at her regular job for the employer until October 28, 2003, when her employment ended due to a layoff.  She then found a job with the Park Nicollet Clinic as an Insurance Selection Specialist in the Registration Department.

During the rest of 2003 and in 2004 the employee treated several times for cervical spine complaints without reporting significant complaints involving the lumbar spine or lower extremities other than occasional tingling and numbness in one or both legs.

In January 2005, the employee sought treatment for an acute flare-up of her cervical spine complaints.  There was no reference to any lumbar complaints. On March 7, 2005, she had a right C5-C6 hemilaminectomy and foraminotomy performed by Dr. Andrew Smith at Methodist Hospital.

In July, 2005 the Employee sought additional medical care for her low back and was treated with epidural injections and physical therapy for low back pain.  In 2005, the employee also received injections for trochanteric bursitis as a result of complaints of bilateral hip pain.

On January 6, 2006, the employee was evaluated by Dr. Michael Manning for her right hip pain.  The pain had initially improved somewhat with physical therapy, but the employee had recently developed increased pain after manipulation.  The diagnosis was of right hip and SI joint discomfort somewhat suggestive of sciatica but with no objective findings of lumbar radiculopathy.  Conservative therapy was recommended.

On March 10, 2006, the employee was seen by her neurosurgeon, Dr. Smith, for a recurrence of low back and radicular right leg symptoms.  Dr. Smith recorded that “[t]hese were apparently part of the original Work Comp injury.”  On examination, straight leg raising was positive.  There was numbness of the right heel and sole of the foot, but no abnormalities in deep tendon reflexes.  Dr. Smith diagnosed an S1 radiculitis by clinical indications, but noted that an updated MRI scan was needed.

An MRI performed on March 27, 2006, was compared with the prior study from 2002 and showed development of anterolisthesis of L4 to L5 secondary to degenerative changes of the facets, resulting in moderate foraminal stenosis and mild to moderate narrowing of the spinal canal.  Diffuse disc bulging was present at L5-S1with a focal central protrusion but without nerve root compression or displacement.

On April 26, 2006, the employee underwent a right L4-5 epidural and a right L4-5 facet steroid injection which resulted in symptomatic improvement.  On June 13, 2006, she underwent a repeat of the injections.

Later in 2006, the employee was treated for plantar fascitis in both feet, worse on the left than the right.  In June of 2006 she sustained ruptured ligaments and fractures in the left foot while crossing a street.

On November 2, 2006, she reported to her family physician, Dr. Hagerness, that her back pain had grown more severe.  Dr. Hagerness speculated that the employee’s back might have been worsened by a change in body mechanics and altered gait related to the employee’s left foot fracture.  The employee was referred to Dr. Leela Engineer, a physical medicine rehabilitation specialist.  Dr. Engineer saw Ms. Getman on November 3, 2006.  Her diagnosis was lumbar spine degenerative disc disease, L4-5 foraminal and lateral recess stenosis without evidence of specific nerve root compression, L4-5 facet arthropathy, and myofascial pain syndrome with a history of rheumatoid arthritis.  She recommended further conservative therapy including physical therapy.

The employee was reevaluated by Dr. Brutlag on August 21, 2007.  Dr. Brutlag diagnosed chronic left foot and ankle pain and chronic low back pain.  A trial of lumbar sympathetic blocks was recommended.  Dr. Brutlag recommended discontinuing physical therapy.

The employee next saw Dr. Brutlag on January 8, 2008, complaining of numbness, tingling, and weakness in the left leg.  There was decreased sensation over the left lateral calf and medial foot, with moderate weakness of the left extensor hallucis longus.  Hip abduction was moderately weak on the left.  The employee was unable to heel walk on the left,and spasm was was present in the lumbar paraspinous muscles.  Dr. Brutlag diagnosed chronic low back pain with an acute left L5 radiculopathy.  She recommended a repeat MRI of the lumbar spine.

The MRI was performed on January 9, 2008.  It showed a slight increase in the anterolisthesis at L4-5, with a resultant mild increase in the central canal stenosis at that level.  Moderate bilateral neural foraminal stenosis was also present at that level.  There was spondylolisthesis with moderate to severe central right-sided stenosis and neural foraminal narrowing.  There was moderate neural impingement causing impingement of the exiting L4 nerve roots, right greater than left.  At L3-4 there was a broad-based disc bulge with mild to moderate central canal stenosis.  Other than mild increase in the central stenosis at L4-5, the scan was read as essentially unchanged from the scan done in March 2006.

The employee was evaluated for low back and bilateral leg pain and numbness by Dr. Ensor Transfeldt on February 25, 2008.  Dr. Transfeld noted by way of history that the employee had experienced chronic intermittent low back pain for many years, but in August 2007 had a severe episode of pain followed by increasing leg pain and by the development of left leg weakness starting in December.  The left leg pain was associated with foot drop.  Dr. Transfeldt further noted that the employee was accompanied by a QRC, having had a work injury in 1996.  On examination, Dr. Transfeldt found definite weakness of ankle dorsiflexion on the left, which he speculated might be related to the employee’s recent foot surgery.  There was generalized numbness in the left leg.  Dr. Transfeldt diagnosed degenerative listhesis at L4-5 with spinal stenosis and nerve root deficits.  Dr. Transfeldt recommended a steroid injection to help with the employee’s pain but told her that her condition would require surgery.

The employee filed a claim petition on February 25, 2008, seeking approval for the proposed surgery as well as temporary total disability compensation from January 8, 2008.

Dr. Transveldt performed posterior L4-5 decompression and fusion on May 12, 2008. The pre-operative diagnosis was multilevel disc degeneration with degenerative listhesis at L4-5 and spinal stenosis at L4-5 with central subarticular and foraminal stenosis.

Following the surgery, the employee reported to Dr. Transfeldt on June 9, 2008, that she felt improvement in her back and leg pain with decreased numbness.  The doctor’s examination showed slight weakness of the left anterior tibialis, but improved compared to her preoperative status.  Dr. Transfeldt recommended rehabilitation and physical therapy, and projected that she would recover from the surgery in about three to four months.

On July 27, 2008, the employee was seen for an examination on behalf of the employer and insurer by Dr. Terry Hood.  After taking the employee’s history, reviewing the medical records, and conducting a physical examination, Dr. Hood concluded the employee's low back condition which necessitated her surgery could not have resulted from the single traumatic event she described as having occurred twelve years earlier.  He found as particularly significant that the employee did not seek treatment for low back symptoms or report any documented complaints related to her lumbar spine for almost a year after the claimed date of injury.

On September 23, 2008, a hearing on the employee’s claim petition was held before a compensation judge at the Office of Administrative Hearings.  Following the hearing, the compensation judge found that the employee had failed to establish by a preponderance of evidence that the work injury of October 16, 1996, was a substantial contributing factor to the development of the employee’s disabling low back condition and related surgery.  The employee appeals.

The compensation judge found that the employee had failed to establish by a preponderance of evidence that the work injury of October 16, 1996, was a substantial contributing factor in the development of the employee’s disabling low back condition and related surgery.  The compensation judge stated in the findings that he had adopted the expert medical opinion of Dr. Hood.

Questions of medical causation fall within the province of the compensation judge.  Felton v. Anton Chevrolet, 513 N.W.2d 457, 50 W.C.D. 181 (Minn. 1994).  It is the function of the compensation judge to resolve conflicts in expert medical testimony, and the choice of expert opinion is usually upheld unless the facts assumed by the expert in rendering the opinion are not supported by the evidence.  Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  Where evidence is conflicting or more than one inference may reasonably be drawn from the evidence, the findings of the compensation judge are to be upheld.  Redgate v. Sroga's Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).

The employee argues, however, that the compensation judge’s findings are not supported by substantial evidence.^[1]  The employee first contends that Dr. Hood’s opinion was based on an incorrect understanding of the medical evidence and thus lacked adequate foundation.  Specifically, the employee argues that Dr. Hood mistakenly assumed that the employee had no complaints referable to the lumbar spine for almost a year following the October 16, 1996, work injury.  The employee points out that she testified that she had experienced pain in her low back and legs immediately following the work injury, and that she continued to experience these symptoms up to the date she first mentioned these symptoms to her physicians on September 8, 1997.  She also notes that the history she gave to the physicians on that date supports her testimony by apparently linking the low back symptoms to the 1996 injury.

Dr. Hood’s opinion did not focus on the employee’s testimony and recollection of symptoms, but on the absence of any medical records documenting the symptoms or any low back treatment.  Specifically, Dr. Hood discounted the employee’s account of her symptoms on the basis that she “was seeing multiple treating physicians at the time and had ample opportunity to express complaints referable to the lumbar spine; however, such complaints were not seen until approximately one year following the claimed injury.”

The compensation judge was not required to accept the employee’s testimony as to her symptoms, and was free to find that the contemporary medical records were better evidence as to whether or not she was experiencing significant low back symptoms during the year following the work injury.  The judge’s adoption of Dr. Hood’s opinion strongly suggests that he did not give great weight to the employee’s claim of ongoing low back problems during the 11 months following the injury.  Given the evidence set out in those medical records, we cannot conclude that Dr. Hood’s opinion was based on facts contrary to those found by the judge.  Accordingly, we conclude that Dr. Hood’s opinion had sufficient foundation to serve as the basis for the compensation judge’s decision.

The employee next argues that the compensation judge failed to notice or consider brief statements on causation by some of her treating physicians, who in various reports either summarily identified the employee’s low-back condition as work-related or relied on the history the employee gave them to attribute the onset of the low back condition to an October 1996 work injury.  The employee points to the language of Finding 30, in which the compensation judge stated that the employee “failed to provide a medical causation opinion that the employee’s work injury of October 16, 1996, caused the employee’s need for the claimed fusion surgery or an opinion that the October 16, 1996, personal injury is a substantial contributing factor in the development of the employee’s low back symptoms . . . which the surgery is to cure and relieve.”  She contends that this language demonstrates that the judge either was unaware of some portions of the evidence or applied an overly strict standard which unreasonably disregarded medical opinions on causation merely because they were summarily stated and failed to provide a detailed explanation.

In McBride v. Anderson Power & Equip., Inc., slip op. (W.C.C.A. Feb. 21, 2002), we noted that a doctor's causation opinion need not be expressed in any particular words, so long as it appears from the doctor's words, considered as a whole, and in light of the evidence in the case, that the doctor was of the opinion that it was not merely possible that the employee's work could have caused the employee's injury, but that it was probable that it did in fact cause the injury.  A failure to identify or explain the specific mechanism of injury does not render a causal relationship opinion legally insufficient.  Rather, the presence or absence of such testimony goes to the weight that may be afforded the opinion by the compensation judge.  All that is required is, under the facts of the case considered as a whole, that it appears a competent medical witness opined the injury causally contributed to the disabling condition.  See, e.g., Goss v. Ford Motor Co., 55 W.C.D. 316 (W.C.C.A. 1996).

However, under the facts of this case, and given the cursory nature of the “causation” statements and “work-related injury” attributions on which the employee relies, we believe that the compensation judge could reasonably have concluded that these statements did not meet even this minimal standard.  The evidence contrary to the employee’s claim included not only a detailed medical opinion and explanation, but also consisted of a one-year gap between the work injury and any treatment or recorded complaints of low back symptoms, during which time the employee had seen her physicians for numerous other medical problems. In addition, there was a period of ten years between the work injury and the emergence of the serious symptoms ultimately requiring surgery.  There were also references in the medical records of non-work incidents or conditions that could explain the employee’s diagnosis.  Given this evidence, we do not find it inappropriate for the compensation judge to comment on the lack of expert opinion in support of the employee’s claim.

We conclude that the compensation judge’s determination has substantial support in the record and we affirm.