The employee appeals from the compensation judge’s determination that she failed to establish her right hip condition and need for surgery was related to her employment.  We reverse.

The employee, Annette Satrum, began working for the employer, the City of Minneapolis, in its public works department as a construction maintenance laborer beginning in June 1999.  The job was heavy, requiring extensive shoveling, and occasionally using a jackhammer.  The employee had a pre-employment physical before beginning to work for the city and no restrictions or concerns were noted.

On November 9, 2005, the employee climbed up on the wheel of a dump truck to retrieve tools that were in the bed of the truck.  When she jumped back down, she stated that she “felt something pull in my back and it really hurt.”  The employee reported the incident to her supervisor and then left the worksite to obtain medical help.

The employee went to Occupational Medical Consultants because “that’s where the city’s doctors are located” and the initial history from that facility was that the employee was being sent for an “evaluation” of the injury.  The employee told the doctor that she had pain in her right groin and in her left lower back and some pain into her left leg.  The diagnosis was “1. strained right groin.  2. left lumbar strain.”  She was given pain medication and work restrictions.  The employee returned for medical care on November 14 with continued symptoms and Dr. Thomas Jetzer’s impression was left lower back and thigh strain.  Therapy was prescribed.  Dr. Jetzer released the employee without restrictions on November 18 and concluded that the employee’s “left lumbar strain” was resolved.

The employee returned to the clinic in January 2006, however, and reported that her pain had never resolved.  She still had pain in her left lower back and into the left leg.  On exam, the employee had pain with external and internal rotation of the left hip.  A left hip strain and lumbar radiculopathy were diagnosed and an MRI was ordered.

The MRI of the lumbar spine showed what was described as “mild to moderate multilevel disc degeneration.”  No nerve root impingement was shown.  An MRI was done on February 24, 2006, which showed “advanced osteoarthritis within the left hip with a moderate-sized joint effusion and evidence of diffuse synovial hyperplasia.”  The MRI also demonstrated “moderate osteoarthritis within the right hip with focal areas of abnormal signal intensity within both acetabular and femoral subchondral bone.”

The employee returned to Dr. Jetzer on March 2, 2006.  She reported her pain had gotten worse and the pain was mostly in her left hip.  She also had some pain, however, in her right hip.  His impression was “1. Multilevel degenerative disc disease and osteoarthritis of the spine.  2. Osteoarthritis of both hips, left worse than the right.  3. Previous injury.  4. Injury to the low back and left hip.”  His opinion, as set forth in the chart note, reads, “It is my opinion that she suffered an injury in November but is (sic) appears that she has very extensive preexisting disease in both of her hips and in her back. She appears to be older than her age and therefore I consider that her injury should be a temporary aggravation of a pre-existing condition.”  It should be noted that Dr. Jetzer’s reference to a previous injury is not supported by any other evidence in this matter.

The employee was referred to Dr. Peter Hanson at Sports and Orthopedic Specialists and saw him on March 20, 2006.  On examination, Dr. Hanson noted that the employee was walking with a limp and he found decreased range of motion in both hips with external and internal rotation.  He stated “I believe that her injury from 11/9/2005 aggravated an underlying condition.  It is possible that her work as a laborer contributed to the degeneration of her hip.”  Dr. Hanson recommended an intra-articular hip injection and some therapy aimed at the hip.

Dr. Hanson apparently saw the employee again on April 5, but only part of his chart note, including his recommendation from that date is in the record.  He referred her for further consultation and she saw Dr. Christopher Larson on April 10, 2006.  Examination and review was limited to the left hip.  Dr. Larson recommended a total hip arthroplasty.  The employee was referred to Dr. Thomas Nelson at Twin City Orthopedics to determine if other treatment options existed.

She saw Dr. Nelson who concluded that a left hip replacement arthroplasty was necessary.  Dr. Nelson performed that procedure on January 31, 2007.  Dr. Nelson also provided the employee’s follow-up care.

The employer accepted liability for the employee’s left hip condition and paid wage loss benefits, permanent partial disability, and medical expenses.

The employee was provided with rehabilitation services and Dr. Nelson’s records indicate that on March 22, 2007, he sat down with the employee and her QRC and “reviewed her job description in detail.”  Dr. Nelson placed detailed restrictions on the employee’s work with the city and released her to return to work.  The employee testified that when she went back to work, she was assigned janitorial duties at the city’s water treatment plant.  The employee described her duties as involving a “lot of footwork” primarily cleaning and mopping floors.  The employee testified “my other hip started bothering me a little bit and I was kind of afraid to say anything because I wanted to keep my job so I just kept on working.”

The employee was terminated by the city in March 2008; she was advised there was no work for her within her restrictions.  The employee testified that at the time of her termination she was experiencing right hip pain.

The employee first treated specifically for her right hip pain on March 12, 2009, when she saw Dr. Nelson.  Dr. Nelson concluded that the employee was in need of a right total hip arthroplasty.  He also stated, “it is again my opinion based on the records that I have reviewed and also my history and examination of the patient that the right hip is also a permanent aggravation of preexisting degenerative arthritis.  Clearly, the work-related accident accelerated her arthritis and the need for eventual surgical treatment.”

The employer denied liability for the employee’s right hip condition and the employee filed a claim petition.

Dr. Nelson provided deposition testimony for the hearing.  When asked about his conclusion that the employee’s right hip condition was related to her employment, he stated “that’s what happened based on her activity level.  I think she probably had some underlying osteoarthritis, but her work as a laborer for the water department clearly accelerated the pace of degeneration of the hip and the need for surgery, the need for treatment.”  He further explained the mechanism of how the employee’s heavy physical activity on the job resulted in accelerated degeneration of the hip joint.  On cross-examination, he was asked about other possible causative factors such as smoking, but Dr. Nelson’s response was that smoking was not shown to be a causative factor in the employee’s condition.

The employee’s claim petition was heard by Compensation Judge Bradley Behr on June 23, 2009.  The employee was the only witness testifying at the hearing. The employee relied on the opinion of Dr. Nelson.  The employer did not obtain an independent medical examination, relying on the comments of Dr. Jetzer as found in his chart notes.  In his findings and order, the compensation judge denied the employee’s claim, concluding that the employee had failed to establish her claim by a preponderance of the evidence.  The employee appeals.

The employee argues on appeal that the compensation judge erred in finding that she had failed to prove a Gillette^[1] injury to her right hip from her employment with the city.  She contends that the compensation judge improperly rejected the opinion of her treating doctor.  In response, the employer claims that the compensation judge’s decision is based on substantial evidence when considering the record as a whole.

At the beginning of the hearing, the employee set forth the basis of her claim.  She alleged that the heavy physical work of her employment had aggravated a degenerative condition in her hips, resulting in a compensable injury on November 9, 2005.  The employee’s claim was supported by her treating orthopedic surgeon, Dr. Nelson, and by Dr. Peter Hanson, who saw her in March 2006.  The employer relied entirely on Dr. Jetzer’s chart note from March 2, 2006, that the employee’s injury was a temporary aggravation of her preexisting condition.

In order to establish a Gillette injury, the employee must demonstrate a causal relationship between the employee’s ordinary work activity and the disablement.  Steffen v. Target Stores, 517 N.W.2d 579, 581, 50 W.C.D. 464, 467 (Minn. 1994).  Further, “the question of a Gillette injury primarily depends on medical evidence.”  To prevail on a claim, the employee must prove the claim by a preponderance of the evidence.  “Preponderance of the evidence means evidence produced in substantiation of a fact which, when weighed against the evidence opposing the fact, has more convincing force and greater probability of truth.”  Minn. Stat. § 176.021, subd. 1a.  (Emphasis added.)

Dr. Nelson, the employee’s treating orthopedist, provided the support for the employee’s claim. He stated in his October 30, 2007, report and in his deposition before the hearing that the employee’s work aggravated her degenerative condition in both hips and necessitated hip replacement surgery.  Dr. Nelson had performed the left hip replacement, which the employer had agreed was work-related.  He had met with the employee and her QRC and discussed in detail the employee’s job duties.  He had reviewed the employee’s prior medical records including the records of Dr. Hanson from March 2006 which noted abnormal findings in both hips.  In his deposition testimony, he explained the mechanical process by which the employee’s work led to an aggravation of her degenerative condition. The use of a jackhammer and jumping in and out of trucks, activities Dr. Nelson knew were part of the employee’s job, placed increased stress on the hip joints and, as a result, had accelerated the degenerative process in both hips.

There was no medical opinion opposing Dr. Nelson.  The employer relied on Dr. Jetzer’s opinion as set out in his chart note from March 2, 2006. The compensation judge did not adopt Dr. Jetzer’s opinion or even refer to it in his decision.  Even the employer had not adopted Dr. Jetzer’s opinion since, if it had done so, it would not have paid for the left hip replacement surgery. Further, we note that Dr. Jetzer’s opinion would seem to lack foundation because his opinion is based, in least in part, on an incorrect history of a “previous Injury.”

Nevertheless, the compensation judge did not accept Dr. Nelson’s opinion and denied the employee’s claim. The compensation judge referred to the employee’s age, her smoking history, arthritic changes in her spine, and the lack of reported right hip symptoms. There is no evidence, however, that any of these factors have any medical significance in the present case. The compensation judge was essentially inserting his own medical opinion on causation. “The finder of fact in a workers’ compensation proceeding is not free to disregard unopposed medical testimony because such testimony concerns issues not within the realm of knowledge of the fact finder.” Ruether v. State, Mankato State Univ., 455 N.W.2d 475, 478, 42 W.C.D. 1118, 1122 (Minn. 1990).

The compensation judge also questioned Dr. Nelson’s opinion because Dr. Nelson did not cite medical studies, diagnostic testing, clinical findings, or subjective complaints which would support his conclusions.  The employee argues that this imposes a burden of proof not required by Steffen and that under the compensation judge’s rationale, it would be impossible to know what evidence would be deemed sufficient to prove a Gillette case.  We agree. In the absence of any contrary medical opinion, there was no basis for the compensation judge to reject Dr. Nelson’s well-founded opinion.

We reverse and order payment of the benefits which the parties stipulated at the hearing were reasonable and necessary.