JEAN O. KUISLE, Employee/Appellant, v. SUNRISE ASSISTED LIVING a/k/a KARRINGTON ASSISTED LIVING and ROYAL & SUN ALLIANCE INS. CO., Employer-Insurer, and MN DEP=T OF HUMAN SERVS., Intervenor.
WORKERS= COMPENSATION COURT OF APPEALS
OCTOBER 2, 2002
EVIDENCE - EXPERT MEDICAL OPINION. The compensation judge=s rejection of all the opinions of the employee=s treating and evaluating physicians other than Dr. Park, based on lack of foundation, was clearly erroneous.
EVIDENCE - CREDIBILITY. Where it appears that the sole basis of the compensation judge=s denial of claims for the employee=s alleged right leg and foot injury is the compensation judge=s belief that the employee could not have and did not observe her right foot turning inward at the precise moment of the incident on November 8, 1999, that finding and determination are clearly erroneous.
WAGES - CALCULATION. Where the compensation judge provides no explanation as to why, in determining the employee=s earning capacity, he considered the employee=s previous part-time employment for the employer, when in fact she worked full-time at the time of the injury when calculating a weekly wage rate, the matter is remanded to the compensation judge for reconsideration of the wage rate and for specific findings outlining the basis for his determination of the wage rate.
Affirmed in part, vacated and remanded in part.
Determined by Rykken, J., Pederson, J., and Stofferahn, J.
Compensation Judge: James R. Otto.
MIRIAM P. RYKKEN, Judge
The employee appeals from the compensation judge=s denial of her claim for various benefits allegedly due as a result of a work-related injury on November 8, 1999, arguing that the compensation judge erred in denying all claims based on his conclusions that the employee sustained a temporary aggravation of her low back condition on November 8, 1999, and that she sustained no injury to her right leg, foot and heel on that date. The employee also appeals from the finding that the employee=s weekly wage on November 8, 1999, was $284.50 and that her earnings from a separate employer from April 30, 1999, through August 6, 1999, are not relevant wages to be considered in determining the employee=s weekly wage. We affirm in part, vacate in part, and remand in part to the compensation judge for reconsideration.
This appeal arises from a work-related injury that the employee, Ms. Jean O. Kuisle, sustained on November 8, 1999. On that date, the employee sustained an admitted injury to her low back and also claims to have sustained an injury to her right lower extremity. As described below, she has undergone medical and chiropractic treatment prior to her 1999 injury, including treatment for low back and right leg and foot symptoms, following previous work-related injuries.
The employee underwent training as a licensed practical nurse in the early 1960's and has worked as a nurse or personal care attendant since then. Following a March 1961 tobogganing accident, and again in 1963, the employee was treated at the Mayo Clinic for complaints of numbness in her right leg and low back pain. On October 24, 1975, the employee sustained a work- related injury while transferring a patient at Desert Samaritan Hospital in Arizona. She noted pain in her low back and right leg following this injury and received medical treatment for a few months post-injury.
On August 11, 1979, the employee sustained a work-related injury while working at Rochester State Hospital. She noted pain in her low back, radiating into her right leg, and in her right shoulder, and was diagnosed as having chronic myofascial pain syndrome. The employee initially consulted a physician at the Olmsted Medical Center following this injury, and testified that she received chiropractic treatment from Dr. Thomas Boisen thereafter. She also received treatment at the Mayo Clinic following her 1979 injury. The employee remained off work for most of the next six years; she was provided retraining benefits and completed her B.S. degree in social work at the College of St. Theresa. By November 1984, Dr. Keith Campbell, Mayo Clinic, assigned a permanency rating of A5% of the whole person for the low back syndrome and 5% of the whole person for the right upper limb symptoms@ in Aaccordance with the AMA Guide to the Degree of Impairment.@ In October 1985, the employee entered into a full, final and complete settlement of her workers= compensation claim pertaining to her 1979 injury.
In June 1987, the employee received medical treatment for right foot and ankle pain and tenderness. The record contains no further references to right foot pain until December 27, 1990, when the employee sustained another work-related injury while working for Shamrock In-Home Care. According to the employee=s testimony, she noted low back pain radiating into her right buttock and right thigh, calf and heel following this injury, symptoms similar to those she experienced following her 1975 and 1979 work-related injuries. Following this 1990 injury, the employee was paid 6.8 weeks of temporary total disability benefits in addition to temporary partial disability benefits. She again consulted physicians at the Olmsted Medical Center, including Dr. Larry Grubbs, occupational medicine specialist. Dr. James Allen, neurologist, examined the employee on January 31, 1991, and diagnosed a Avery minimal disc bulging due to the incident@ in December 1990. He recommended continued traction and home exercises. Dr. James Smith also conducted a neurological examination of the employee on October 11, 1991. Dr. Smith noted that the employee walked with an antalgic gait; she reported right heel pain if her heel touched the floor. Dr. Smith diagnosed the employee as having A[b]ack pain of indeterminate etiology. No evidence for a neurologic lesion.@ He prescribed continued physical therapy and Elavil to assist with sleeping.
In 1992, Dr. Robert Wengler, who examined the employee upon referral of her attorney, assigned a rating of 14% permanent partial disability to the spine, and assigned work restrictions of no lifting over ten pounds and avoiding repetitive bending and stooping and prolonged sitting. The employee continued her physical therapy through at least July 1993. In 1993, the employee settled her workers= compensation claims pertaining to her 1990 injury on a full, final and complete basis.
In July 1993, the employee noted pain in her right foot. Dr. Grubbs stated that the pain was Apossibly secondary to the persisting back pain and altered gait.@ On July 22, 1993, Dr. Dr. Loring Stead, podiatrist, diagnosed A[p]es cavus with plantar fascial strain. Peroneus brevus tendinitis.@ In September 1993, Dr. Richard Salib examined the employee at the referral of Dr. Grubbs; the employee reported low back, right buttock and right foot pain. Dr. Salib recommended diagnostic imaging studies of the sacroilliac joint, but there is no indication in the record whether those diagnostic tests were performed. The employee underwent further physical therapy, from approximately July 1994 until March 1995. In his chart note January 27, 1995, Dr. Grubbs stated that the employee had a chronic low back pain secondary to sacroiliac dysfunction, and that she should maintain her 20 pound lifting restriction. On June 14, 1995, the employee consulted Dr. Richard Christiana, occupational medical specialist, reporting persistent low back pain and pain in her right buttock and right heel. Dr. Christiana diagnosed chronic low back pain. In response to his questions, the employee advised Dr. Christiana that she could work but not sit for more than 30 minutes or stand for more than 45 minutes.
In the records of the Olmsted Medical Clinic generated between June 1995 and September 1997, there is no further reference to the employee=s low back condition, other than two references to prescription refills for pain medication.
In August 1997, the employee began working as a licensed practical nurse and personal care attendant for Sunrise Assisted Living, also known as Karrington Assisted Living, (the employer). In September 1997, Dr. Grubbs conducted a pre-employment physical examination of the employee and determined that she could perform the physical duties required by the employer which were, in the employee=s opinion, strenuous. According to testimony by the employee and a representative of the employer, while working as a nurse for the employer prior to her 1999 injury, the employee regularly lifted 50 to 70 pounds in the course of her work, and her duties included repetitive bending, lifting of laundry baskets, and personal care work for patients including diapering and dressing patients. On January 26, 1999, the employee underwent a complete physical examination at the Olmsted Medical Clinic, and in the course of providing a history to the doctor, reported Alower back discomfort on occasion.@ However, there is no record of any additional treatment for those low back symptoms prior to late November 1999.
On November 8, 1999, the employee sustained an admitted injury to her lumbar spine in the course of her employment for the employer. The employee also claims that she sustained an injury to her right leg, foot and heel at the same time. The employer was then insured for workers= compensation liability by Royal & Sun Alliance Insurance Company (the insurer).
At the time of her injury, the employee worked full-time for the employer and had done so since August 20, 1999. Since 1998, the employee had worked essentially full-time hours, through a combination of two part-time jobs as a nurse with both Pine Haven Nursing Home and the employer. By August 20, 1999, the employee had resigned her part-time position at Pine Haven, and worked full-time and overtime hours for the employer.
On November 8, 1999, the employee and two co-workers worked with a patient who was diagnosed with Alzheimer=s disease, attempting to teach him how to walk again. The patient stood with a walker in front of him. The employee faced the patient and held on to his gait or transfer belt; two co-workers stood on each side of the patient, holding onto him and to the frame of the walker. As the employee began walking backwards and encouraged the patient to walk forward, the patient attempted to sit down, causing the employee to be pulled forward and bent over the walker bar. According to the employee=s testimony, she pulled on the patient=s gait belt to protect him from falling, and noted an immediate pulling and throbbing sensation in her right buttocks extending into her right leg. That same night and the following morning, the employee noted significant pain in her low back, right foot and right heel.
On November 16, 1999, the employee obtained treatment from Dr. Thomas C. Boisen, D.C., with whom she had last treated in 1979. The employee reported right low back pain with burning pain into her right leg, commencing a week earlier. Dr. Boisen recommended that the employee work on a light duty basis, if available, or otherwise remain off work a few days. Thereafter, on November 28, 1999, the employee sought emergency room treatment at Olmsted Medical Center Hospital, complaining of low back pain with radicular pain in her right leg and heel; she was prescribed pain medication.
On December 1, 1999, the employee consulted Dr. Christiana, reporting continued low back pain, right lateral thigh pain and pain in her right heel. Dr. Christiana diagnosed Aright trochanteric bursitis, right Achilles tendinitis, and low back muscle strain, resolving,@ and restricted the employee to sedentary work, with restrictions of avoiding bending, twisting, squatting and climbing. By December 8, 1999, Dr. Christiana prescribed crutches to avoid weight bearing with the right foot, and provided work restrictions of occasional ambulating and no squatting or climbing. He prescribed physical therapy to treat her right trochanteric bursitis and right hip pain. By December 30, 1999, Dr. Christiana restricted the employee to four hours of sedentary work per day.
Following her injury, the employee continued to work on a light-duty, part-time basis, within restrictions assigned by her treating physicians. Due to ongoing symptoms, the employee received continued medical treatment at Olmsted Medical Center, including physical therapy and neurological, podiatric and orthopedic consultations. On January 5, 2000, Dr. James Smith, who had last examined the employee in October 1991, conducted a neurological examination and diagnosed musculoskeletal and heel pain. He stated that the employee=s examination was normal, and that the employee=s symptoms were Aatypical and nonanatomic, and nearly perfectly mirror similar [symptoms] from 1991.@ He recommended an EMG of the right leg, which had normal findings, and recommended continuation of the same work restrictions recommended by Dr. Christiana. He also noted in his chart that the employee Arecovered from similar [symptoms] over a relatively long period of time in 1991, but apparently w/o residual.@
On January 10, 2000, Dr. Christiana revised the employee=s work restrictions to Alight-duty@ status for six hours per day. He released her to work without restrictions by January 24, 2000. However, the employee was again assigned work restrictions by Dr. Stead, who examined her on February 4, 2000, and diagnosed plantar fascial strain with some neuropraxia of the right heel. He administered steroidal injections into her right heel, and recommended an equalizer brace for her right foot, massage and a light stretching and strengthening exercise routine. Dr. Stead concluded that the employee=s injuries to her right foot, heel and leg Awere the direct result of trying to maintain the position of a client during a fall.@ By February 15, 2000, Dr. Stead restricted the employee to six hours of work per day. By April 26, 2000, Dr. Stead assigned work restrictions of Aworking three days on, one day off, six hours maximum per day.@ He later revised those restrictions to include Aactivities to tolerance, two days off, three days on stretch with a 6-7 max per hours, with two hours off sitting or other light duties throughout the day.@ Dr. Stead referred the employee to physical therapy to treat her right foot and heel symptoms. The employee continued follow-up treatment with Dr. Stead.
On July 27, 2000, the employee was examined by Dr. H. William Park at the request of the employer and insurer. Dr. Park concluded that the employee sustained a soft tissue muscle strain in her lower lumbar spine on November 8, 1999, which resolved after two months of conservative treatment. He found no evidence that the employee sustained a localized tendinitis involving the Achilles tendon or plantar fasciitis of traumatic origin as a result of that injury. He determined that the employee had reached maximum medical improvement from her injury approximately 2 2 months post-injury, by January 24, 2000, and recommended no further treatment.
On October 2, 2000, Dr. Matthew Eich, orthopedist, examined the employee, and diagnosed a A[r]ight Achilles tendon injury with subsequent tightening of secondary forefoot overload with Morton=s neuroma phenomena and metatarsalgia as well as mid-foot strain. Probable stress fracture and low back strain.@ Dr. Eich prescribed crutches and a cane, and referred the employee for a bone scan to assess her foot problem and an MRI of her lumbar spine, which she underwent on October 6, 2000. Dr. Eich concluded that the employee=s right leg and foot and low back conditions resulted from her work-related injury in November 1999. By October 9, 2000, Dr. Eich restricted the employee entirely from work. He ultimately referred her to an orthopedic foot and ankle specialist, Dr. Lowell Lutter.
Dr. Lutter, along with Dr. Diane Palkert, initially examined the employee on January 2, 2001. Dr. Lutter referred the employee for an MRI of her right foot, which showed inflammatory changes at the fourth metatarsal. Dr. Lutter diagnosed right anterior tendinitis and chronic low back pain, and recommended physical therapy, lumbar sympathetic blocks to treat the pain in her lower extremity, and an orthotic for her right foot.
In a report dated March 8, 2001, Dr. Eich stated that the employee Awas not capable of returning to her occupation as a practical nurse care giver for Alzheimer patients as she was doing prior to the injury.@
On May 4, 2001, the employee was re-examined by Dr. Park, who concluded that the employee=s November 8, 1999, injury was a temporary low back strain that was a temporary aggravation of her pre-existing condition. Dr. Park concluded that there was no evidence that the employee sustained any structural injury to her right foot or heel, nor any soft tissue injury of a chronic nature, as a result of her injury on November 8, 1999. Dr. Park opined that the degenerative changes in the employee=s mid foot, detected on an MRI scan conducted in January 2001, were related to the employee=s preexisting condition. Dr. Park concluded that the conservative treatment the employee received for her back for six weeks post-injury, and the MRI scans of the employee=s low back and foot, were reasonable and necessary diagnostic tests. However, he recommended no further medical or chiropractic treatment other than stretching exercises for the right ankle. Although Dr. Park restricted the employee from lifting more than fifty pounds, he stated that the restriction is due to the employee=s preexisting condition and not to her injury dating back to November 1999. Dr. Park encouraged the employee to return to gainful employment to avoid chronic pain syndrome.
In his report of May 22, 2001, Dr. Lutter opined that there was a causal relationship between the employee=s November 1999 injury and her ongoing disability, stating as follows:
There is a connection between the injury sustained November 8th 1999, while working for Sunrise Assisted Living and the condition she is being treated for currently. It is my opinion that the injury that she sustained on November 8th 1999 is the same problem that she is now being treated for. The basis of this is that the mechanism of injury, the progression of symptoms, and physical examination are all consistent with her diagnosis of tendinitis, which was triggered by the injury to her ankle. This lead to an alternation of gait and the ankle tendinitis.
Dr. Lutter concurred with Dr. Eich=s earlier work restrictions that had restricted the employee from work since October 9, 2000.
In a claim petition filed on February 8, 2001, the employee claimed various benefits as a result of her work-related injury of November 8, 1999, including temporary partial disability benefits between July 30 and October 8, 2000, temporary total disability benefits thereafter, and payment for medical and rehabilitation expenses. In their answer to the claim petition, the employer and insurer admitted that the employee sustained a temporary low back strain on November 8, 1999, which had resolved, and denied that the employee sustained a right leg, foot or heel injury on November 8, 1999.
This matter was addressed at hearing on August 29, 2001. In addition to extensive hearing testimony by the employee and deposition testimony by a representative of the employer, evidence included medical records and reports from numerous physicians and clinics, including records of the Olmsted Medical Group from 1979 - 2001, the Mayo Clinic, Fairview Red Wing Clinic and Hospital, Desert Samaritan Hospital, Dr. James Allen, Dr. Robert Wengler, Dr. Richard Salib, Dr. Matthew Eich, Dr. Loring Stead, Dr. Lowell Lutter, and Dr. Thomas Boisen, D.C.
In findings and order served and filed October 4, 2001, the compensation judge found that the employee sustained an injury to her low back on November 8, 1999, in the nature of a temporary aggravation of her pre-existing condition. He found that the employee had reached maximum medical improvement (MMI) from that injury prior to July 7, 2000, and that notice of MMI was served on the employee on July 24, 2000. He found that the employee=s wage was $284.50. The compensation judge determined that the employee=s part-time wages earned for Pine Haven from April 30 through August 6, 1999, were not relevant for calculating the employee=s weekly wage. The compensation judge denied the employee=s claim for temporary total or temporary partial disability benefits from and after July 29, 2000, and denied her claim for payment of unpaid medical expenses and unpaid rehabilitation expenses, concluding that those expenses were not causally related to the employee=s personal injury of November 8, 1999. The employee appeals.
STANDARD OF REVIEW
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 (1992). 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 the 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).
"[A] decision which rests upon the application of a statute or rule to essentially undisputed facts generally involves a question of law which [the Workers' Compensation Court of Appeals] may consider de novo." Krovchuk v. Koch Oil Refinery, 48 W.C.D. 607, 608 (W.C.C.A. 1993).
Nature of November 8, 1999, Injury
The employee appeals from the compensation judge=s findings that the employee sustained a temporary aggravation of her pre-existing low back condition as a result of her work related injury on November 8, 1999, and that she sustained no right leg or foot injury on November 8, 1999, and from his denial of her claim for temporary total or temporary partial disability benefits after July 29, 2000, medical treatment expenses, and rehabilitation expenses.
The compensation judge found, in pertinent part, that the nature of the employee=s injury on November 8, 1999, was Aa temporary aggravation type personal injury involving her lumbar back only,@ that the employee was not entitled to temporary disability benefits from and after July 29, 2000, to the date of hearing, and that AMs. Kuisle=s unpaid treatment expenses and unpaid rehabilitation expenses are not causally related to her temporary aggravation type personal injury of November 8, 1999." (Findings Nos. 2, 4 and 11.) The compensation judge further found that
Ms. Kuisle=s testimony and the medical histories she gave to her treating and her examining physicians subsequent to November 8, 1999 were not accurate histories and the opinions based on the histories given were not based on a proper foundation (no motion to take live testimony was made).
Ms. Kuisle=s testimony has not been received as fully credible.
(Findings Nos. 9 and 10.)
The issue before this court is whether the compensation judge=s findings are supported by substantial evidence of record, and are not clearly erroneous. "The burden is on the employee to prove by a fair preponderance of the evidence that she is entitled to workers' compensation benefits." Fisher v. Saga Corp., 463 N.W.2d 501, 501, 43 W.C.D. 559, 560 (Minn. 1990). In addition, Ain order to recover workers' compensation benefits, the employee must establish that his work-related injury is a substantial contributing factor to his current disability." Steinhaus v. F.B. Clements, 47 W.C.D. 22, 30 (W.C.C.A. 1992).
The compensation judge rejected all of the employee=s treating physicians= opinions as lacking foundation and accepted only Dr. Park=s opinion. The medical evidence of record includes opinions from various treating physicians that the employee=s injury on November 8, 1999, including an injury to her lumbar spine and right leg and foot, substantially contributed to her ongoing disability following that injury. By contrast, Dr. Park concluded that the employee=s November 8, 1999, lumbar spine injury was temporary in nature and had resolved, that it no longer substantially contributed to the employee=s ongoing disability, and that the employee sustained no right leg or foot injury on November 8, 1999.
The employee argues that her November 8, 1999, injury substantially aggravated her pre-existing condition, resulting in a more disabling condition, more stringent physical work restrictions, and the need for more extensive medical treatment than she required before that injury. She argues that she required no medical treatment for her low back, right leg, right sciatica, or right foot pain between midsummer 1995 until her injury on November 8, 1999. She states that in September 1997, Dr. Grubbs had conducted a pre-employment physical examination of the employee and determined that she could perform the physical duties required of her position as a nurse for the employer.
The employer and insurer argue that the employee failed to provide her treating physicians an accurate medical history involving her pre-1999 low back pain, citing to various references in her medical records. Based on these alleged omissions in the employee=s medical histories, the employer and insurer argue that Dr. Park is the only physician who based his opinions on the employee=s complete medical history, that Dr. Park=s opinion is based on proper foundation and is supported by substantial evidence of record, that the compensation judge properly rejected all medical opinions other than Dr. Park=s, based on lack of foundation, and that the employee failed to meet her burden of proof.
By contrast, the employee argues that she provided an adequate history of her previous injuries to her various doctors, contrary to the compensation judge=s finding that she had not done so. The employee=s post-1999 medical records contain references to the employee=s previous injuries and comparisons between her earlier symptoms and post-injury symptoms; the employee points to these medical records as proof that she provided an adequate history to her treating and examining physicians, and that her treating doctors had sufficient history and medical records available for review to support their opinions.
The compensation judge agreed with the employer=s position, and specifically found that the employee=s testimony had Anot been received as fully credible.@ In his memorandum, the compensation judge outlined his review of the employee=s records and concluded that:
Ms. Kuisle=s failure to give to her treating and examining doctors her prior medical history involving her low back pain and her right leg pain subsequent to November 8, 1999 portrays Ms. Kuisle as a person who has not been honest with any of her treating or examining physicians. All medical opinions on causation from treating or examining physicians have little value as they were given without adequate foundation.
(Memo, p. 6) In denying the employee=s claims, the compensation judge rejected all medical opinions except Dr. Park=s.
Where a compensation judge=s determination is based upon a choice between differing medical opinions, this court must affirm where the opinion relied upon has adequate foundation. Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985). However, a Adoctor's opinion regarding causation which is based on an inadequate factual foundation is of little evidentiary value." Winkles v. Independent Sch. Dist. #625, 46 W.C.D. 44, 58 (W.C.C.A. 1991) (citing Welton v. Fireside Foster Inn, 426 N.W.2d 883, 41 W.C.D. 109 (Minn. 1988)). To be of evidentiary value, a medical opinion must rest on a factual basis. Zappa v. Charles Mfg. Co., 260 Minn. 217, 224, 109 N.W.2d 420, 424, 21 W.C.D. 459, 467 (1961). Furthermore, the facts upon which the expert relies for his or her opinions must be supported by the evidence. McDonald v MTS Sys. Corp., 43 W.C.D. 83 (W.C.C.A. 1990), summarily aff'd (Minn. July 13, 1990). The failure to comment on the details of an employee=s history does not render a doctor=s opinion invalid, and a medical expert need not be aware of all of the exact details of the employee=s previous medical history before the doctor may render an opinion. Minor facts may be unknown to a doctor without damaging the foundation for the medical opinion as long as the omissions do not mislead the fact-finder. Scott v. Southview Chevrolet Co., 267 N.W.2d 185, 188, 30 W.C.D. 426, 431 (Minn. 1978). In general, such deficiencies go only to the persuasiveness or weight to be given the opinion, not to its admissibility. See Drews v. Kohl=s, 55 W.C.D. 33, 39 (W.C.C.A. 1996); see also Bossey v. Parker Hannifin, slip op. (W.C.C.A. Mar. 14, 1994); Trego v. Associated Leasing, slip op. (W.C.C.A. Jan. 9, 1998); Stuhr v. Northwestern Travel Serv., Inc., 57 W.C.D. 352 (W.C.C.A. 1997); summarily aff=d (Minn. Dec. 15, 1997).
In denying the employee=s claim, the compensation judge focused extensively on the employee=s histories as reflected in her medical records. Our review of the record shows that the employee=s testimony is generally consistent with notations in her medical records, and that some of her post-1999 medical records refer back to earlier medical treatment and symptoms. Of significant note is that the employee consulted physicians at the Olmsted Medical Clinic for general medical treatment, and for treatment following work injuries, since at least 1975. This is not a case where the bases for the various doctors= opinions are unknown or where the doctors made unsupported material assumptions in rendering causation opinions. In addition, the competence of a witness to render expert medical testimony depends both upon the degree of the witness= scientific knowledge and the extent of the witness= practical experience with the matter at issue. Reinhardt v. Colton, 337 N.W.2d 88, 93 (Minn. 1983). The employee=s treating physicians presumably had available to them the employee=s medical chart generated since 1975. They had opportunities to examine the employee, review her medical records and take a history from her.
Under these circumstances, there was foundation for the medical opinions in the record and the compensation judge erred in rejecting all medical opinions other than Dr. Park=s on foundation grounds. See, e.g., Olson v. Menasha Corp., 59 W.C.D. 14 (W.C.C.A. 1998) (where a doctor Areviewed and described many of the pertinent medical records, findings, and test results, and he personally performed a detailed examination of the employee,@ there clearly was foundation for that doctor=s opinion and the compensation judge erred in rejecting his opinion on foundation grounds). The compensation judge erred by rejecting the employee=s claim for lack of properly founded supporting medical opinions. We therefore vacate and remand the matter to the compensation judge for reconsideration in light of all the evidence, including the opinions of those physicians other than Dr. Park.
The compensation judge also found that the employee was not credible when testifying about the description of how her right leg and foot injury occurred on November 8, 1999, and denied her claims related to her right leg and foot condition based on his assessment of the employee=s credibility. He concluded that
Most damaging to Ms. Kuisle=s credibility was her testimony at the hearing held August 29, 2001 that when her incident occurred on November 8, 1999 her right foot turned inward when she was suddenly placed in a position of supporting an Alzheimer patient who fell backward before being caught by two nursing aides. I do not believe Ms. Kuisle could have or did observe her right foot turning inward at the precise moment of the incident, nor do I believe that her right foot did, in fact, turn inwardly.
(Memo., p. 6.)
The employee disputes the compensation judge=s conclusion that she could not have, and did not, observe the exact mechanism of her right foot injury on November 8, 1999. The employee argues that there was no evidentiary support for that determination, and argues that the exact mechanism of the injury is irrelevant. She argues that the relevant issue is whether the injury, in whatever manner it occurred, caused an aggravation of the employee=s low back, right sciatica, right leg and right foot injuries.
We agree that, in this particular case, the exact mechanism of the alleged foot injury on November 8, 1999, does not dictate the ultimate determination of whether the employee sustained an injury that caused the employee=s subsequent foot and heel symptoms. It appears there is no dispute that an incident occurred. The employee=s treating and examining physicians obtained a history from the employee about the actual incident and her ongoing symptoms post-injury. In addition, although the employee had obtained medical treatment in the past for her right foot, she has received more extensive medical treatment for her right foot and heel since her 1999 injury, and various physicians have diagnosed her condition following her 1999 injury as including a right Achilles tendon injury, subsequent tightening of secondary forefoot overload with Morton=s neuroma phenomena and metatarsalgia, mid-foot strain, and plantar fascial strain with some neuropraxia of the right heel. These diagnoses are not listed in the employee=s medical records prior to her 1999 work injury.
We acknowledge that it is the trier of fact's responsibility to assess the credibility of a witness, and a finding based on credibility of a witness will not be disturbed on appeal unless there is clear evidence to the contrary. Tolzmann v. McCombs-Knutson Associates, 447 N.W.2d 196, 198, 42 W.C.D. 421, 424 (Minn. 1989) (citing Even v. Kraft, Inc., 445 N.W.2d 831, 835, 42 W.C.D. 220, 225 (Minn. 1989)). However, the issue presented here was not whether the employee credibly testified exactly how her foot injury occurred, but whether the employee injured her right foot and, if so, whether that injury substantially contributed to her ongoing disability. The compensation judge summarily concluded that the employee sustained no injury of any type to her right foot or leg on November 8, 1999, but made no specific findings regarding that alleged injury. Instead, based on his conclusion that the employee=s testimony and histories provided to physicians were inaccurate because she did not advise them of her pre-1999 medical history, he concluded that the employee=s claims, including her claim based on her right leg and foot condition, are not compensable.
We therefore conclude that the compensation judge=s denial of the employee=s claims of a right leg and foot injury, based solely on his conclusion that she could not have observed the position of her foot at the time of her injury on November 8, 1999, is not supported by substantial evidence. Accordingly, we vacate and remand to the compensation judge for reconsideration of the employee=s claims in view of all of the evidence of record, including all medical opinions and records. On remand, the compensation judge should make specific factual findings regarding the causation of the employee=s alleged right foot and leg injury and should explain the evidentiary basis for those findings. The compensation judge should reconsider this matter based on the existing record.
Weekly Wage Claim
The employee appeals from the compensation judge=s determination that her weekly wage on November 8, 1999, was $284.50. At hearing, the parties submitted the employee=s wage information covering the period between April 30 and November 8, 1999. The employee essentially worked full-time hours through a combination of two part-time jobs until August 20, 1999. From August 20 until November 8, 1999, the employee worked full-time solely for the employer. At Finding No. 8, the compensation judge found that the only relevant wages for calculating the employee=s weekly wage on the date of injury were those wages the employee earned for the employer, and found that the employee=s wage rate was $284.50.
The employer and insurer initially admitted a wage rate of $360.00 and paid temporary disability benefits based on that wage. At hearing, however, the employer and insurer alleged that the proper wage rate was $284.50, apparently based on an average of the employee=s part-time, full-time and overtime wages earned from the employer during the 22 weeks preceding November 8, 1999, utilizing the calculation method set forth in Minn. Stat. ' 176.011, subd. 3.
The employee claims a wage rate of $652.60, based on a 26-week average of her wages earned from both Pine Haven and the employer, since she had worked for both during a portion of the 26 weeks prior to her November 8, 1999, injury. Although the employee worked solely for the employer on November 8, 1999, she claims that her weekly wage rate should be based on an average of her earnings from both Pine Haven and the employer. Alternatively, the employee claims that her weekly wage should be based on an imputed full-time hourly rate of $11.00, alleging that even though the employer promised that higher wage when offering her the full-time position, she was never paid that rate, and was paid only $9.00 per hour on the date of her injury.
The object of a wage determination is to arrive at a fair approximation of the employee=s probable future earning power which has been impaired or destroyed by the injury. Sawczuk v. Special School District 1, 34 W.C.D. 282, 312 N.W.2d 435 (Minn. 1981). See also, Bradley v. Vic=s Welding, 39 W.C.D. 921, 405 N.W.2d 243 (Minn. 1987); Beissel v. Marschall Line, Inc., 58 W.C.D. 470 (W.C.C.A. 1998). AWhile the computation of weekly wage is frequently based upon actual wages, there are various circumstances which make the claimant=s actual earnings during a particular period an unreliable measure of his future earning power.@ Bradley, 39 W.C.D. at 924, 405 N.W.2d at 246.
Based on payroll records in evidence, during the 2-week pay periods encompassing August 20 and November 8, 1999, the employee=s hours varied from 70.5 to 105.5. Her regular pay during those 2-week pay periods ranged from $600.75 to $945.00. In addition, her overtime earnings each pay period ranged from $6.75 to $236.25. Although the employee was working full-time and overtime hours for the employer at the time of her injury, and had done so since August 20, 1999, the compensation judge concluded that the employee=s weekly wage on November 8, 1999, was $284.50, but does not explain how he reached this conclusion. The compensation judge apparently considered the employee=s wages earned from the employer during the 22-weeks preceding her injury, which included a period of time when she worked part-time for the employer. The compensation judge provides no explanation as to why, in determining the employee=s earning capacity, he looked at her previous part-time employment for the employer, when in fact she worked full-time on the date of injury and had done so since August 20, 1999. It is evident that, in this case, using only a portion of part-time wages when calculating a weekly wage rate results in a wage rate that does not accurately reflect the employee=s earning capacity, since she was earning full-time wages at the time of her injury.
Therefore, we vacate the compensation judge=s finding that the employee=s weekly wage on November 8, 1999, was $284.50, and vacate his related finding concerning the employee=s claim for an underpayment of benefits. We remand this issue to the compensation judge for reconsideration of the employee=s wage rate and the employee=s claim for an underpayment of temporary disability benefits, and for specific findings outlining the basis for his determination of the wage rate.
 The only reports in the record from Dr. Boisen are dated November 16 and 29, 1999. Dr. Boisen=s November 16th chart note record states that Ms. Kuisle was previously seen 10-15 years ago.
 Dr. Wengler refers to a 14% permanent partial disability of the spine referable to a herniation or possible stenosis. It appears that this is a typographical error and was intended to state disability of the whole body. The permanency rules in effect at the time of the employee=s 1990 injury allow a rating of 14% permanent partial disability of the whole body for either a herniated disc or stenosis at one vertebral level, provided that certain objective findings are present.
 Dr. Stead=s July 22, 1993, chart note does not specify which foot he examined. His July 29, 1993, chart note refers to the employee=s left foot. However, it appears that the employee=s primary foot complaints were in her right foot, based on the history she provided to Dr. Grubbs and later to Dr. Salib.
 The employee=s hourly rate on the date of injury was $9.00. The employer and insurer apparently based their initial calculations of the employee=s wage on full-time work at 40 hours per week, which calculates to $360.00.
 Although the statute requires that calculations be based on 26 weeks prior to an employee=s injury date, in this case the Karrington/Sunrise payroll records in evidence only extend back 22 weeks prior to the employee=s injury date.
 The employee bases her claim on a $359.25 weekly wage at Pine Haven and a $293.35 weekly wage at Karrington/Sunrise from June.