The employer appeals from the judge’s findings that the employee’s right knee condition was permanently aggravated by a work-related injury, that the work injury was a substantial contributing cause of the employee’s need for a total knee replacement, that the employee had not reached maximum medical improvement, and that the employee reasonably refused a job offer.  Finding substantial evidence to support the judge’s findings, we affirm.

The employee was working for Minneapolis Public Schools, Special School District 1 [the employer] as a bus driver when she was involved in a motor vehicle accident on November 9, 1994.  The employee was also involved in a work-related accident on April 25, 1997.  At that time, she injured both of her knees, her low back, and her neck.^[1]  She treated with Dr. Douglas Becker and underwent surgery on her left knee in July of 1997.

In August of 1998, the employee underwent an MRI of the right knee, and, about two months later, on October 15, 1998, Dr. Becker performed arthroscopic surgery.  His post-operative diagnosis included degenerative changes of the knee.

The employee returned to work as a bus driver after this surgery, received no treatment, and had no further difficulties with her neck, low back, shoulders, or knees until the injury at issue in this case.  Dr. Richard Strand performed an independent medical examination on behalf of the self-insured employer on May 18, 1999, and stated that the employee’s knee condition “should not restrict her driving a bus.”

On May 26, 2009, the bus the employee was driving was struck by a car.  The employee sought medical treatment on May 28, 2009, from physician assistant Mary Anderson, for pain in her left shoulder and right knee, explaining that she had been driving a bus that was stopped when it was hit by a car and that she had been tensed up at the time of impact.  She also gave a history of a prior right knee injury.

The employee returned to PA-C Anderson on June 4, 2009.  The office note from that date indicates that the employee denied having struck her knee in the accident but indicated that she had been tense when impact occurred.  The employee complained of right knee pain and edema and was advised to remain off work.

The employee was seen by Dr. Ronald Tarrel of the Noran Clinic on June 10, 2009, complaining of a severe headache, neck pain, and back pain with radiation into the right leg to the big toe.  The form that the employee filled out at the time of that examination also noted that she was experiencing knee pain and gave a history of prior knee surgeries.  She was diagnosed with a cervical sprain and lumbar sprain as a result of the 2009 accident.

The employee was seen by Dr. Becker on June 15, 2009, for left shoulder and right knee pain.  At that time, the employee related that her right knee had made impact with the dashboard of the bus at the time of the collision.  Dr. Becker diagnosed right knee chondromalacia of the patella and left impingement syndrome/AC strain and restricted the employee from bus driving through August 1, 2009.

When seen at Noran Clinic on July 8, 2009, the employee noted that, at the time of impact in the May of 2009 accident, she had been pushing her feet hard on the brake.  Certified nurse practitioner Ann Rechtzigel opined that the employee’s right knee pain and swelling “may be related to the impact and from stepping on the brake so hard.”

When seen in follow-up at Dr. Tarrel’s office on July 29, 2009, the employee continued to complain of neck pain, shoulder pain, low back pain, and right knee pain.  It was noted that the employee was treating with Dr. Becker for her knee condition.  She was to remain off work through August 31, 2009.

On August 17, 2009, the employee was seen by PA-C Anderson again.  On that date, the employee reported that she was “better,” and examination of her knee was described as “normal.”  PA-C Anderson discontinued physical therapy and noted that the employee would be returning to work as a bus driver on September 1.

When she returned to Dr. Tarrel on August 31, 2009, the employee continued to have some neck and back pain, and the doctor continued to diagnose cervical and lumbar sprains.

When seen by Dr. Becker on October 7, 2009, the employee complained of severe ongoing symptoms in both her left shoulder and right knee.  Dr. Becker opined that surgical treatment for the right knee condition was reasonable and restricted her from bus driving.

Dr. Becker performed an arthroscopic surgery on the employee’s right knee on November 19, 2009.  At the time of the surgery Dr. Becker found advanced degenerative changes in the knee.  On December 2, 2009, he recommended that the employee observe restrictions on bending, twisting, stooping, standing, and squatting.^[2]  Physical therapy for the employee’s right knee condition was scheduled but later cancelled due to “insurance issues.”

The employee was seen in Dr. Tarrel’s office on January 12, 2010, complaining of persistent neck pain with intermittent discomfort and numbness in the left upper extremity down into her hand.  She also reported persistent generalized low back and lower thoracic pain and spasm.  Physical therapy was ordered, and a physical therapy assessment was performed on January 25, 2010.  Two treatments per week, for four to five weeks, were recommended.  However, there is no record indicating that the employee had that physical therapy.

Dr. Christopher Meyer performed an independent medical examination of the employee on January 29, 2010, for the employer.  With regard to the employee’s right knee, Dr. Meyer reported that the employee had described pushing very hard on the brake at the time of the impact on May 26, 2009, or perhaps hitting her knee on the steering column; she was not certain.  Dr. Meyer opined that the employee was suffering from age-related degenerative joint disease of both knees, resolved cervical and lumbar strains, left shoulder strain, age-related degenerative disc disease of the neck, and extreme pain behaviors.  It was also his opinion that any symptoms in the employee’s back and neck had resolved by August 17, 2009, and that any symptoms occurring thereafter were not related to the 2009 accident.  He further concluded that the employee’s significant degenerative changes in the right knee “may have been flared up after a motor vehicle accident, but [were] not caused by a motor vehicle accident.”  According to Dr. Meyer, any flare up of the employee’s right knee symptoms had resolved by August 17, 2009, and any symptoms beyond that point were related to degenerative joint disease.  He opined that the employee could have returned to work without restrictions as of October 7, 2009,^[3] and that the employee had reached MMI from the 2009 motor vehicle accident on August 17, 2009.

On February 9, 2010, the employee began physical therapy for her right knee condition.  The record of that visit noted that the employee was complaining of increased pain and difficulty with walking, sitting, using stairs, and making transitional movements.  From March 18, 2010, through May 5, 2010, Dr. Becker continued to restrict employee’s work activities, including restricting her from bus driving.  On March 12, 2010, the employee was re-evaluated by Dr. Tarrel.  It was his opinion that the employee continued to suffer from a chronic neck and back injury that was work-related.  He kept her off of work through mid April.

On March 31, 2010, the employee underwent another MRI of the right knee.  About a week later, on April 5, 2010, the employee and Dr. Becker discussed the advisability of total knee replacement surgery.

The employee was seen again in Dr. Tarrel’s office on April 7, 2010, regarding neck, back, and headache pain.  The employee reported that she had returned to work the day before but was fighting an escalating headache.  CNP Ann Rechtzigel gave the employee a note recommending that she work four hours per day, five days per week, with restrictions.  Physical therapy was again recommended.

On April 14, 2010, Dr. Becker wrote a letter stating that, as of April 5, 2010, the employee’s right knee remained symptomatic “as a result of the May 26, 2009 work exposure and work injury.  That particular injury was a work related motor vehicle accident that caused a contusion of the right knee.  This led to significant knee discomfort, swelling, and symptoms requiring arthroscopic microfracture.”  Dr. Becker went on to describe progressive discomfort and dysfunction in the employee’s right knee since the injury, and he opined that the employee had suffered a permanent aggravation of her right knee as a result of the May 2009 injury, which had led to the need for additional treatment, including the recommended total knee replacement.  The employee’s restrictions at the time included no bus driving.

In his June 7, 2010, office note, Dr. Becker again continued the employee’s previous restrictions and noted that the employee had returned to work in a non-bus driving position.  He also noted, however, that the employee had been experiencing increasing pain and was using a cane full time.  He again recommended a total right knee replacement.

Dr. Meyer reviewed additional medical records and issued an addendum to his report on June 8, 2010.  He reiterated that MMI had been reached by August 17, 2009, agreed that the employee needed a right total knee arthroplasty for her significant degenerative joint disease, but denied that the May 2009 injury was a substantial contributing cause of the employee’s need for that surgery.

On February 18, 2010, the employer wrote to the employee, advising that, per the opinions of Dr. Meyer, the employee was expected to return to work as a bus driver on February 22, 2010.  A notice of intention to discontinue workers’ compensation benefits [NOID] was filed on March 1, 2010, when the employee failed to report for that job.  An amended NOID filed on March 2, 2010, added that the employee had reached MMI and had been served with notice of MMI on February 27, 2010.

The NOID proceeded to an administrative conference, and, in an order on discontinuance, the employer was allowed to discontinue benefits based solely on the employee’s attainment of MMI.  As to the employer’s other basis for discontinuance, it was determined that the employee had reasonably refused the bus driving job based on her treating doctor’s recommendation.  The employee filed an objection to discontinuance, seeking temporary total disability benefits continuing from February 17, 2010, and a claim petition seeking authorization for the right knee replacement surgery.  The employer filed a petition to discontinue, disputing the judge’s conclusion that the employee’s job refusal was reasonable.  The objection to discontinuance and petition to discontinue were consolidated by order dated June 3, 2010.  When those matters came on for hearing before a compensation judge, the parties agreed also to litigate the employee’s request for a total knee replacement.

In findings and order filed on October 19, 2010, a compensation judge found that the 2009 work incident permanently aggravated the employee’s preexisting right knee condition, that the employee had not reached MMI from her neck, low back, and right knee conditions, that the employee had reasonably refused the employer’s job offer, and that a total right knee replacement was reasonable, necessary, and causally related to the employee’s 2009 work injury.  The employer appeals.

On appeal, the employer contends that substantial evidence does not support the compensation judge’s finding that the employee’s right knee condition was permanently aggravated in the May 2009 incident.^[4]  We are not persuaded.

The records and reports of Dr. Becker support the judge’s findings.  Dr. Becker treated the employee’s right knee in 1998, performed arthroscopic surgery on that knee in October of 1998, and resumed treatment of the employee’s right knee on June 15, 2009.  In a letter written on April 14, 2010, Dr. Becker referred to the employee’s May 26, 2009, motor vehicle accident, indicating that it had caused a contusion of the right knee that had led to “significant knee discomfort, swelling, and symptoms requiring arthroscopic microfracture.”  He further reported that the employee had experienced progressive discomfort and dysfunction in the right knee since the injury, that, by April 5, 2010, her symptoms were quite severe, and that the MRI scan findings were consistent with progressive degenerative changes in her knee.  In his opinion, the employee had suffered a permanent aggravation to her right knee as a result of the May 2009 accident.

In her memorandum, the compensation judge applied the factors delineated in Wold v. Olinger Trucking, Inc., slip op. (W.C.C.A. Aug. 29, 1994), in analyzing whether the employee’s injury was temporary or permanent.  While acknowledging that the employee had degenerative joint disease prior to the 2009 accident, the judge noted that the employee had gone without treatment for ten years, she had been successfully employed as a bus driver during that period, she had no restrictions on her work activities prior to her 2009 work injury,^[5] and that, since the 2009 injury, she had had significant symptoms, treatment, and restrictions.  The employer apparently does not dispute the judge’s analysis.  Rather, the employer relies on the argument that Dr. Becker’s opinions lack of foundation.

The employer contends that Dr. Becker did not have adequate foundation for his opinions because he failed to review all of the employee’s medical records, the employee’s deposition transcript, and Dr. Meyer’s two reports.  The employer also contends that Dr. Becker based his opinion on the erroneous assumption that the employee had hit her knee during the course of the May 2009 accident.  Again, we are not persuaded.

We concede that the histories contained in the medical records regarding the employee’s 2009 injury are not entirely consistent.  Noran Clinic recorded that the employee was pushing down on the brake with both feet at the time of impact.  Dr. Becker recorded that the employee’s knee made contact with the steering column.  The employee told Dr. Meyer and testified at hearing that she may have hit her knee on something, but was not certain, but that she knew that she experienced the onset of right knee pain in the 2009 accident.  The precise “nature of the injury” does not appear to be relevant, however.  While Dr. Meyer noted that “it is very difficult for me to understand the mechanism and the velocity of the injury to her knee,” he went on to find that the employee’s preexisting degenerative changes of the knee “may have been flared up” by the motor vehicle accident in 2009.  Injuries are compensable either if the employment substantially causes a condition or if a work injury substantially aggravates or accelerates a preexisting condition.  Wallace v. Hanson Silo Co., 232 N.W.2d 363, 28 W.C.D. 79 (Minn. 1975); Vanda v. Minnesota Mining & Mfg. Co., 218 N.W.2d 458, 27 W.C.D. 379 (Minn. 1974).

Dr. Becker treated and operated on the employee’s right knee in 1998, conducted examinations of the employee beginning in 2009, obtained a history from the employee that is similar to that taken by Dr. Meyer, and reviewed x-rays and MRIs of the employee’s right knee.  As a general rule, this level of knowledge establishes the doctor’s competence to render an expert opinion.  See Grunst v. Immanuel-St. Joseph’s Hospital, 424 NW2d 66, 40 W.C.D. 1130 (Minn. 1988).  Dr. Becker’s failure to review all records containing conflicting accounts of the accident is not fatal under these particular facts. 

The employer contends that Dr. Meyer’s opinion is better founded.  However, this court generally will affirm a compensation judge’s choice between expert opinions unless the facts assumed by the expert in rendering his opinion are not supported by the evidence.  Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  We find no basis to overturn the judge’s decision on this issue.

The employer first contends that temporary total disability benefits should cease because the employee failed to respond to the employer’s February 4, 2010, job offer.  However, this was not an issue presented to the compensation judge at hearing.  While the employer’s brief on appeal provides specifics about an offer for an office job, we could find no evidence in the record on this topic.  As such, the employer’s argument regarding a February 4, 2010, job offer is not properly before us.

The issue at hearing was the propriety of the job offer made by the employer on February 18, 2010, calling for the employee to return to full-time bus driving.  Substantial evidence supports the judge’s finding that the employee did not unreasonably refuse this offer.  Specifically, at the time of this job offer, the employee was operating under a restriction against driving a school bus, which had been issued by Dr. Becker on February 2, 2010, and was to be in effect through March 17, 2010.  In addition, during the weeks before and after the job offer, the employee was undergoing physical therapy for her right knee and was complaining of constant right knee pain and increased difficulty sitting and bending/straightening her knee.  Given this evidence, we affirm the judge’s finding that the employee did not unreasonably refuse the employer’s offer of a school bus driving job.

On the issue of MMI, the employer again contends that Dr. Becker’s opinion lacks foundation and that the opinion of Dr. Meyer has better foundation and should be adopted.  This argument has already been addressed above.

Maximum medical improvement is defined as “the date after which no further significant recovery from or significant lasting improvement to a personal injury can reasonably be anticipated, based upon reasonable medical probability, irrespective and regardless of subjective complaints of pain.”  Minn. Stat. §176.011, subd. 25.  At the time of Dr. Meyer’s MMI report, the employee was under direction to have physical therapy for her right knee, but insurance would not cover it.  In addition, she had been referred to physical therapy for her cervical and lumbar spine complaints, but that therapy never took place.  Finally, since the issuance of Dr. Meyer’s report, the employee has been advised to undergo a total knee replacement.  Given these circumstances, it was not unreasonable for the compensation judge to conclude that the employee had not reached MMI from the effects of her work injury.

The employer’s only argument on this issue is that Dr. Becker’s opinions lacked foundation.  Having found that Dr. Becker had foundation for his opinions, we affirm the judge’s finding that the recommended right knee replacement surgery is reasonable, necessary, and causally related to the work injury.