The employer and insurer appeal from the compensation judge’s findings as to the nature and extent of the employee’s admitted injury, and from the determination that the employee is entitled to payment of claimed temporary total disability benefits, to rehabilitation assistance, and to payment of reimbursement for medical expenses.  We affirm.

The employer, Contingent Work Force Solutions, managed kitchen operations at the Minnesota state prison at Stillwater.  In 2009, the employee, Cheryl Arne, was hired by the employer as a food service supervisor.  In 2012, she was promoted to the position of food service director.  This position included overseeing the kitchen facility at the prison, supervising both co-workers and the prisoners who worked in the kitchen.

The employee sustained an admitted personal injury on January 30, 2013, when she was assaulted by an inmate.  The employee testified at hearing that she had only a limited recollection of what happened immediately preceding and during this assault.  She was talking with co-workers and prison employees in the dining hall, standing near a steel fence used to control inmate movement.  An inmate came over and started to argue with one of her co-workers.  He was quite agitated.  One of the prison guards came up and stood to her right.  The employee recalled that the inmate then “squared up” and that she heard a “smash noise,” after which she regained consciousness and saw the guard lying face down in blood.  The employee realized that she was on the floor and that her left leg hurt.

The assault and its aftermath were caught on security video.  The video shows an inmate in an animated discussion with the employee and other workers.  The inmate is seen attacking a prison guard and knocking the prison guard unconscious to the ground with a single punch; then turning to the employee, pushing her with his left hand, and apparently punching the side of her head with his right fist.  The employee is seen to fall backwards.  It appears that she may be striking the back of her head on a metal barrier before falling to the floor, but the angle of the camera view does not allow this to be determined with absolute certainty.  When paramedics arrive, the employee is seen to be left sitting on the floor for an extended period while their attention is first focused on the injured prison guard.

The employee then was lifted into a wheelchair and taken by ambulance to the emergency room at the River Falls Hospital in Wisconsin, where she complained of left knee pain and a minor headache.  The employee's left knee was tender, and x-rays of the employee’s left knee showed a moderate effusion, but it was felt that her prior knee replacement was still intact.  Examination showed the employee to be fully oriented.  She was noted to exhibit “abnormal recent memory” and to appear anxious.  A CT scan of the employee’s head conducted on that date was interpreted as being normal.  The employee was provided with a knee immobilizer and discharged.

The employee received extensive physical and occupational therapy for orthopedic and vision conditions, and was diagnosed with a possible traumatic brain injury and Post Traumatic Stress Disorder.  Her overall care has been overseen by Dr. Lynn Miller at the Midwest Spine Institute, who initially examined the employee on April 23, 2013.  On that date the employee reported headaches and pain in her neck, low back pain, and mid scapular area, right hip and right buttock pain.  Dr. Miller diagnosed a traumatic brain injury, left-sided occipital neuralgia, and disc herniation at the C3-4 and C5-6 levels with left C6 radiculopathy and questionable left C4 radiculopathy.  Dr. Miller also diagnosed possible cranial pathology, a neuropsychological delay post traumatic brain injury, and post-traumatic stress.

The employer and insurer first admitted a left knee injury, and later admitted temporary strains to the employee’s neck, back, and left knee, but denied liability for any other claimed injuries.  On August 26, 2014, the matter was submitted to a compensation judge for hearing.  The record closed on January 15, 2015, and the judge issued her findings and order on a number of contested issues including (1) the nature and extent of the work injury, (2) the attainment of maximum medical improvement, (3) the reasonable, necessary and causal relationship between the disputed medical treatment and the injury, and (4) the entitlement to temporary total disability compensation from and after June 26, 2013.  In her findings and order, served on March 6, 2015, the compensation judge found that the employee had sustained injury to her left knee, low back, and neck and had developed a vision problem and a psychological condition as a result of the injury.  The judge found that the employee had not reached maximum medical improvement, and that all of the employee’s medical, chiropractic, and psychological treatment was reasonable, necessary, and causally related to the work injury.  The employer and insurer appeal.

The medical evidence relating to the various conditions is extensive.  For clarity, part of that evidence is summarized below and divided into categories by body parts or conditions.

The employee has a long history of left knee problems starting with a skiing accident in 1988.  She subsequently underwent multiple additional surgeries to her left knee culminating in total left knee replacement surgery in 2010 performed by Dr. Rutledge.  There remained some limitation of flexion, at 90 degrees.  The employee was released to work full time on January 31, 2011.  The employee returned to see Dr. Rutledge a few more times in 2011.  Dr. Rutledge released the employee from his care with no physical restrictions in November of that year.  The record shows no additional treatment for the employee’s left knee until after the work injury on January 30, 2013.

The employee reported ongoing left knee pain beginning with and continuing since the work injury.  She reported left knee pain at the emergency room on the date of the January 30, 2013, work injury.  On the next day, she was seen for orthopedic evaluation of her knee pain at the Mayo Clinic in Red Wing, where she had originally treated at the time of her left total knee replacement.  The examining physician’s assistant noted effusion, concluded that the knee was stable, and released the employee to return to work in a sedentary position, with a knee immobilizer and crutches.  By mid-February 2013, the physician’s assistant prescribed physical therapy, restricted the employee from work through at least mid-March 2013 due to her knee condition, and assigned work restrictions thereafter.

The employee later received treatment for her knee from Dr. Boyd at TRIA Orthopedics starting in April 2013.  An MRI of the employee’s left knee on April 4, 2013, showed the employee’s total knee replacement to be in place.  There was moderate soft tissue swelling laterally near the IT band which was considered consistent with a contusion.

In June 2013, Dr. Boyd referred the employee to Dr. Edward Cheng, who examined the employee on September 10, 2013.  Dr. Cheng considered the employee’s examination findings and symptoms suspicious for an MCL laxity post left total knee replacement.  He recommended that the employee either continue physiotherapy and the use of a hinged knee brace and see if her pain resolved, or undergo surgery to assess the degree of laxity in the MCL.  On February 18, 2014, Dr. Cheng conducted a manipulation of the employee’s knee under anesthesia.  That procedure was successful in improving her range of motion in the knee.  The employee received physical therapy at Saunders Therapy following the manipulation procedure.

The employee had sporadic low back complaints prior to the work injury.  Around 1998 she injured her back in a fall from a horse.  In July 2001, she sought treatment for episodic low back pain starting one and a half months previously.  A lumbar MRI showed degenerative disc disease with tearing and bulging at L5-S1 and L4-5.  Her last date of treatment for the 2001 episode was October 16, 2001.  In February 2006, the employee was seen by a chiropractor after developing some low back pain while painting a fence.  X-rays showed chronic degenerative disc disease at L2-3 and L4-5.  There is no record of any follow-up treatment.  The employee was also seen for a single chiropractic visit on March 18, 2011, for pain in the upper back, neck, mid and low back after a lifting incident at home three days earlier.  The record subsequently fails to show any further treatment or new injury to the employee’s neck or low back until the date of the January 30, 2013, work injury.  There is also no evidence that the employee had any permanent restrictions for her neck or low back prior to the work injury.

The employee returned to her chiropractor, Dr. Annette M. Harel, a few days after the 2013 work injury reporting neck, upper back, mid back, and low back pain, in addition to her knee and leg pain.  An MRI of her neck on March 25, 2013, showed a two millimeter right posterolateral protrusion at C6-7 mildly narrowing the central spinal canal with flattening of the cord and accompanied with chronic moderate left and mild right foraminal stenosis.  There was also mid to lower cervical spondylosis with bulging from C2-3 to C5-6, mild central stenosis and cord abutment on extension at C2-3 and right dorsal bulging/protruding at Tl-2.  The scan was also read as showing left facet joint hypertrophic changes at C7-T1.

Dr. Harel referred the employee to Dr. Lynn Miller to evaluate a possible neck injury.  Dr. Miller diagnosed disc herniation at the C3-4 and C5-6 levels with left C6 radiculopathy and questionable left C4 radiculopathy.  The employee underwent an epidural steroid injection at C7-T1 on May 17, 2013.

The employee continued treating with Dr. Harel and other physicians for pain in her neck, upper back, mid back, and low back.  On August 28, 2013, the employee underwent bilateral C3 medial branch blocks.  She underwent a bilateral C1-2 facet joint block at Midwest Spine on June 9, 2014, and a right-sided SI joint injection there on June 23, 2014.  However, the employee denied any relief from this treatment.

In her report of August 11, 2014, Dr. Harel diagnosed the employee with permanent injuries to her low back and neck, as well as to her left knee and brain.  She opined that the employee was unable to return to work.

In April 2013, at her initial examination with Dr. Miller, the employee reported problems with worsening vision and “floaters” in her eye.  She later reported “blurry” vision that had commenced after her work injury.  The employee reported having difficulty reading for greater than 15 minutes of time, and also experienced photophobia.

Dr. Miller referred the employee to a neuro-ophthalmologist, Dr. Marian Rubenfeld, who examined the employee on August 30, 2013.  She assessed her with a closed head injury, presbyopia, photophobia with discomfort, vitreous floaters, convergence insufficiency, and myopia.  Dr. Rubenfeld felt that the employee’s symptoms were characteristic of a traumatic brain injury with microscopic effects not usually visualized on a CT scan or MRI scan.  She referred the employee for occupational therapy to address her vision issues, and prescribed special glasses.

The employee had a history of some previous mental health treatment.  She had been prescribed Paxil for emotional issues dealing with her left knee surgeries, asthma, and the death of her father, and was treated for anxiety related to asthma flare-ups on several occasions during the period from 1998 to 2006.  The employee testified that she was weaned off Paxil prior to the time she began working for the employer.  There is no further mention of treatment for a psychological condition through the date of the work injury on January 30, 2013.

Within a month of the 2013 work injury, the employee told Dr. Harel that she had become very emotional and was quite fearful since the assault.  She was unable to sleep. She also reported depression, anxiety, and memory loss.  Dr. Harel referred the employee to Dr. Elizabeth Goldsmith at Woodbury Allina Clinic, who diagnosed anxiety as an acute reaction to gross stress, and referred the employee for therapeutic counseling.  The employee thereafter continued in ongoing treatment and psychological counseling for anxiety and depression.

In June 2013, the employee was seen by Jonathan Hoistad, a psychologist, at the referral of Dr. Miller.  The employee reported experiencing periods of nightmares and insomnia since her assault.  Dr. Hoistad diagnosed major depression, recurrent, severe and generalized anxiety disorder, and a narcissistic and obsessive compulsive personality.  He concluded that the employee was experiencing stress because of her physical problems and difficulties recovering from the assault incident at work.  He recommended continued medical treatment as well as individual psychological support.

The employee underwent a neuropsychiatric evaluation by Dr. Susanne Cohen at the Noran Neurological Clinic in July 2013.  Dr. Cohen interpreted testing results to indicate that the employee might have difficulty coping with emotional stress, causing her to focus on her physical dysfunction.  In light of the history of the assault, she thought it possible that the employee had sustained a brain injury which had resulted in residual cognitive deficits.  However, she also was uncertain whether the employee’s test results reflected her true abilities.  Dr. Cohen suggested a referral to a brain injury program at Sister Kenny Institute.

The employee underwent occupational therapy at Sister Kenny Institute for her physical condition, her cognitive complaints, and her alleged visual impairments.  On April 9, 2014, the employee was evaluated by Dr. Bradley Helms at Courage Kenny Rehabilitation Associates.  He concluded that the employee continued to show symptoms directly related to her work injury, both from a physical and psychological standpoint.  He recommended continued occupational therapy for her head injury, physical therapy for her knee injury, and ongoing myofascial treatment for her neck and back.

Multiple reports from medical experts were submitted by both parties at the hearing.  The employee submitted medical records from providers who have treated her for various conditions, as well as narrative reports in which they outlined their conclusions.  The employer and insurer had the employee examined by physicians specializing in a variety of medical specialties corresponding with the employee’s various claimed conditions.

Dr. Lynn Miller, who was involved in the employee’s care since early 2013, diagnosed the employee with post-traumatic stress syndrome, a cranial nerve injury, visual pathology, traumatic brain injury, knee pathology, occipital neuralgia, disc herniation, cervicalgia, low back pain, and right groin pain.  She opined that the work injury was the cause of the employee’s continued symptoms and disability, and her need for medical treatment and work restrictions.  Dr. Miller recommended follow-up treatment for the employee, and concluded that the employee is unable to return to her previous job due to PTSD, although she could benefit from returning to a different, light duty job.  Dr. Miller was also of the opinion that the employee had reached maximum medical improvement from her traumatic brain injury, but that she was not yet at MMI for the remaining injuries and conditions.

Psychologists Elizabeth Goodchild and Greg Picker, who were among physicians treating the employee’s psychological issues, opined that the employee continued to experience extreme anxiety and depression secondary to injuries she sustained while working at the prison.  They considered the employee’s reported increased anxiety, panic attacks, and episodes of rage as supportive of a diagnosis of post-traumatic stress disorder and directly related to the work injury. They recommended ongoing mental health treatment.  In their view, the employee was not yet able to work as of their August 2014 report.

In a report dated September 23, 2014, Dr. Helms reiterated his earlier opinions that the work injury had resulted in an injury to the employee's knee, back, and neck, along with possible traumatic brain injury and possible post-traumatic stress.  He thought the employee might eventually need a pain management program.  He opined that she was still unable to return to work in her job.

Dr. Thomas Beniak, a licensed psychologist, examined the employee on behalf of the employer and insurer on October 9, 2013.  He concluded that the employee had sustained, at most, a questionable and exceedingly mild traumatic brain injury from the assault at work.  He found no evidence of neuropsychological deficits or depressive symptomatology.  In his opinion, the work injury did not result in any neuropsychological consequences.  He did not believe that the employee was disabled from work on a neuropsychological basis.  He placed no restrictions on the employee as a function of her neuropsychological status, and opined that the employee had reached maximum medical improvement from a neuropsychological perspective.

On October 17, 2013, the employee was examined by Dr. Alan Weingarden, a neuro-ophthalmologist.  He felt that the employee had an entirely normal eye exam with no residual effects from any head injury.  He found no evidence of convergence insufficiency, exophoria or photophobia, and concluded that the employee’s floaters and presbyopia, myopia, and astigmatism were all normal for the employee’s age.  He did not believe the employee was ever disabled as a result of any eye condition.  He did not believe that the employee needed treatment for a vision condition, nor did he agree with the prescription for special prismatic glasses.

The employee was examined on behalf of the employer and insurer on November 18, 2013, by Dr. Mark Friedland, an orthopedic surgeon.  With respect to an injury to the low back or neck, he concluded that the employee had sustained, at most, “minor and temporary exacerbations of her long-standing documented cervical and lumbar degenerative disc disease in the form of cervical and lumbosacral strain/sprain injuries.”  Dr. Friedland also concluded that the employee sustained only a temporary thoracic strain/sprain injury, and a very mild and temporary left medial collateral ligament sprain, all of which had resolved with no permanent partial disability.  He opined that the employee was at MMI for those conditions.

Dr. Friedland also evaluated the employee’s left knee condition.  He felt that the left knee treatment provided to the date of his examination was reasonable and necessary, except for chiropractic treatment which he deemed excessive.  In his opinion, the employee had not yet reached maximum medical improvement with regard to her left knee injury.  He agreed with Dr. Cheng’s treatment recommendation for manipulation of the left knee under anesthesia, noting that if the employee was found to have arthrofibrosis, she might need six to twelve weeks of physical therapy to increase her range of motion.  On July 21, 2014, Dr. Friedland conducted a follow-up examination of the employee after the recommended left knee manipulation and post-operative physical therapy.  Dr. Friedland then concluded that the employee had fully recovered from a temporary left knee injury upon completing rehabilitation on June 3, 2014.

The employee underwent an independent psychological examination by psychologist Paul Arbisi on March 8, 2013.  Dr. Arbisi felt that the employee did not meet the criteria for PTSD.  He noted the employee’s history as obsessive-compulsive disorder and somatic symptom-related disorder, but concluded that the work injury did not substantially contribute to those conditions.  In his opinion, the employee had not sustained a permanent psychological injury as a result of her work injury.  Dr. Arbisi was of the opinion that any temporary exacerbation of the employee’s underlying anxiety that might have been caused by the work injury would have resolved as of March 20, 2013, and that maximum medical improvement had been reached.  He did not think the employee was disabled from work from a psychological standpoint at any time after the work injury.  He considered psychological treatment through March 2013 reasonable and necessary, as was a referral to Dr. Cohen at the Noran Neurological Clinic to evaluate the employee's cognitive complaints.  He did not believe the employee had required any further psychological treatment after that date.

The Workers’ Compensation Court of Appeals will uphold the factual findings of the compensation judge if they are supported by substantial evidence and were reached through application of the correct legal standard.^[1]  Substantial evidence is such relevant evidence as a reasonable mind might accept as adequate to support a conclusion.^[2]  In reviewing for substantial evidence to support the judge’s findings, we do not make credibility determinations.^[3]  Where the evidence allows reasonable minds to differ as to whether the employee’s injuries remain a substantial contributing factor in the need for continuing medical treatment, the responsibility for that decision rests with the compensation judge.^[4]

In her findings and order, the compensation judge concluded that the employee had sustained injury to her left knee, neck, and low back, and had developed a vision condition and a psychological condition as a result of the work injury.  She found that the employee had not reached maximum medical improvement from her injury, and had been temporarily and totally disabled since June 26, 2013, to the date of the hearing.  The judge also found that all of the employee’s medical, chiropractic, and psychological treatment had been reasonable and necessary.  The employer and insurer appeal.

The first question before us is whether substantial evidence supports the compensation judge’s finding that the employee was credible.  The employer and insurer argue that this case rests on the employee’s credibility, in that doctors with whom she treated relied on her description of the work incident in forming their opinions.  They further argue that, based on the record as a whole, the employee was not credible.

First, they contend that the employee gave contradictory, inaccurate, and misleading statements regarding her injury.  As specific examples, they note that the employee testified that she had not viewed the surveillance video, even though several physicians’ notes state that she had seen a video.  Similarly, in her deposition, she testified that she had not spoken to anyone about how her injury occurred, but later, by the time of the hearing she testified that she had spoken to co-workers about how the injury occurred.  The appellants point out that although the employee denied telling her doctors that she knew how the injuries occurred or that she knew if she had struck her head during the incident, several physicians recorded a history stating that the employee struck her head.  They further point out that the various medical records show somewhat differing accounts of how the employee was injured, ranging from being pushed or thrown to the ground, being hit in the head by an inmate, to striking her head on something, with some records stating the employee struck her head once and others twice.  They argue that the employee’s doctors must have obtained their histories from the employee, and infer from the discrepancies in the histories they recorded that the employee must have given multiple disparate accounts of the injury.  Accordingly, they argue, the compensation judge should have found that the employee lacked credibility.

In further support of their contention that the employee’s testimony was not worthy of credit, the appellants point to testimony in which she claimed that Dr. Weingarden did not use a prism in the eye examination he conducted, and in which she denied that Dr. Friedland had asked her about prior neck or back pain or injuries, although these two physicians’ reports and statements contradict those assertions.  Further, they point out that the employee testified in her deposition that she did not have range of motion difficulties with her left knee in prior treatment before 2013, but that this is contradicted by contemporary records.  They also point out that the employee’s deposition testimony that she had never been advised to stop using an immobilizer or locked hinged brace until more than year after her work injury is contradicted by a Mayo Clinic record from March 13, 2013.

Finally, they assert that some of her healthcare providers have found her less than credible.  Specifically, Dr. Freeman noted on at least one occasion that some of her complaints were subjective and that his objective findings did not support the symptoms she described; and Dr. Boyd on June 10, 2013, similarly noted that her complaints of medial pain did not correlate to his physical findings.  They also point to a chart note by Dr. Cohen dated July 23, 2013, in which he stated that he was unable to rule out a possibility that the employee gave an intentionally poor effort on neuropsychological testing.  Based on all of the foregoing, they argue that the compensation judge erred in finding the employee credible “in any respect.”^[5]

We note, however, that the determination of credibility is a matter entrusted to the finder of fact.^[6]  The judge here could reasonably conclude that any differences in the employee’s accounts of the assault were to be explained in part by the traumatic nature of that experience.  Because the medical records were created not by the employee, but by her medical providers based on their own understanding and interpretation of the history she gave, the compensation judge could further reasonably conclude that minor inconsistencies between the various recitals of the medical history did not necessarily indicate that the employee gave greatly inconsistent accounts to different providers.  The compensation judge expressly found that the various medical histories of the injury were all reasonably consistent with the employee’s testimony.  In any event, we note that the judge was also able to rely on the surveillance videos to assist her in assessing to what extent the employee’s account of the injury was credible.

We conclude that the various inconsistencies cited by the appellants are not of a sufficient degree or nature to render the compensation judge’s credibility determination clearly erroneous.  It was for the compensation judge to determine what weight should be given to any contradictions in the employee’s account of the injury, or in regard to the tangential questions of what various physicians said or did during their examinations.  The judge weighed and resolved these alleged inconsistencies in favor of accepting the employee’s overall testimony as credible.  Under these facts, we are not persuaded by the appellants’ arguments that the compensation judge’s credibility determination should be reversed on appeal.

The employer and insurer also appeal from the judge’s determination that the employee still has ongoing medical and psychological conditions resulting from the work injury and that she was entitled to temporary benefits and rehabilitation.  In reaching these findings, the compensation judge expressly relied on the expert medical opinions of the employee’s treating physicians over those of the employer and insurer’s examining physicians.  As the trier of fact, the compensation judge has the discretion to choose between conflicting medical expert opinions.^[7]  On appeal, the judge’s exercise of that discretion is generally not to be disturbed on appeal unless clearly erroneous or if the opinion relied upon was without adequate foundation.^[8]

The appellants, however, contend that the opinions of the employee’s physicians lacked foundation in that most of them were not provided with a complete set of all the medical records from each of the other treating physicians, as well as all the employee’s medical records predating the date of injury.  They argue that the employee’s doctors were therefore unaware that slightly different accounts of the assault had been recorded by various physicians.  They assert that, had the employee’s physicians been aware that there were slightly different accounts of the assault in the various medical records, the employee’s physicians and experts would have viewed the employee’s account of the incident as lacking credibility.  This argument is essentially a restatement of the employer and insurers’ contention, already discussed, that the employee’s account of the assault was not credible.  We have already stated and affirmed the judge’s express conclusion that the various medical histories of the injury were all reasonably consistent with the employee’s testimony.  There is consequently no obvious foundational defect in the opinions of the physicians who relied on the employee’s history of the assault as foundation for their opinions, since the history they relied upon was accepted by the compensation judge.  The appellants’ assertion that the employee’s medical experts would have changed their opinions on the basis of the variations in the recorded medical histories is largely a conjectural argument.

The employer and insurer further argue that the security video contradicts the history the employee gave to her providers, and argue that the foundation for their opinions was therefore inadequate or incorrect.  It appears to us that the hinge point of this issue on appeal is whether the surveillance video of the incident is, as the appellants claim, wholly inconsistent with the history of the incident as reasonably understood by the medical experts and the compensation judge.  The compensation judge found that the video was consistent with the employee’s testimony.  She also found that the various histories recorded by the employee’s physicians were all reasonably consistent with the incident.

Having viewed the video, we note that there is room for uncertainty about some aspects of the employee’s injury, as not all of the events were clearly visible due to the distance and angle of the camera and the presence of obstructions to a full view of the employee’s body during her fall.  Nonetheless, it appears to us that the judge’s interpretation of the events of the assault is reasonably supported by the video.  The video does show that the employee was first pushed by the assailant and then likely struck on the side of the head by her assailant’s closed fist.  While it is not possible to see definitively whether the employee struck her head as she fell, the way in which she fell and the position of a railing and table make that eventuality highly probable and permit an inference that she did strike her head.  The employee is then seen to remain motionless for a short but sufficient duration to permit the judge to infer that she was rendered briefly unconscious, and to credit her testimony to that effect.  If different inferences can justifiably be drawn from the evidence in the case, the inference drawn by the factfinder will generally not be disturbed on appeal.^[9]

While there is room under these facts to dispute a specific mechanism for the injuries, we conclude that reasonable inferences drawn from the video, together with the employee’s subsequent symptoms and medical test results, adequately supports the foundation for the expert opinions which served as a basis for the judge’s findings.  Substantial evidence supports the compensation judge’s findings based on her choice of medical experts, and we affirm.