The employee appeals from the compensation judge’s Findings and Order denying the employee’s claim for workers’ compensation benefits arising out of  an injury to the low back on January 29, 2003.  We affirm.

Lubomir Petrov, the employee, immigrated to the United States from Bulgaria in October 1994.  The employee testified he has had only about 16 hours of course work in English as a second language, and his ability to speak English is limited.  He was 54 years old at the time of the hearing.  The employee began working as a craft band worker for Twin City Tile & Marble, the employer, in July 1997.  His duties included cutting and polishing granite and marble and, about once a week, delivery and installation of product, primarily countertops, in customer’s homes.

On January 2, 1999, the employee was involved in a non-work-related motor vehicle accident.  He was seen two days later by Leon Frid, D.C.  The doctor noted moderate paraspinal lumbar spasm from L2 to S1 with decreased lumbar range of motion.  Dr. Frid diagnosed a moderate lumbar sprain/strain, prescribed physical therapy and chiropractic manipulation, and took the employee off work.  The employee was examined by Dr. Alexander Axelrod, a family practice physician, on January 5, complaining of severe low back pain with radiation into the legs bilaterally.  Dr. Axelrod prescribed Relafin and Norflex and additionally recommended home exercise.  On January 12, 1999, Dr. Joseph Engel, a rehabilitation medicine specialist,^[1] noted muscle spasm from L1 to S1, pain with supine straight leg raising, a decreased left ankle jerk, and sensitivity over the left sciatic notch and back of the left thigh and calf.  The doctor diagnosed a lumbosacral sprain with tenderness of the left sciatic nerve.

The employee received ongoing treatment at the clinic on a regular basis.  On February 2, 1999, Dr. Frid released the employee to return to work with restrictions of no lifting over 55 to 60 pounds with limited bending and twisting.  The lifting restriction was increased, two months later, to 80 pounds.  In May 1999, Dr. Frid released the employee to conservative care as needed.^[2]  In a report dated May 17, 1999, Dr. Frid observed the employee still had some limitations with bending and twisting but had a favorable course of recovery.  He stated the employee had been able to return to the majority of his work duties with the 80 pound lifting restriction, noting, however that strength loss remained a concern.

David Gottlieb, D.C., performed a chiropractic examination on behalf of the automobile insurer in June 1999.  The employee complained of continuing problems with low back pain, grading the pain at a seven, along with right leg paresthesia.  He reported constant back pain with difficulty moving and lifting secondary to pain.  On examination, the doctor noted no significant clinical findings but marked pain complaints with any testing maneuver.  Dr. Gottlieb diagnosed a musculoligamentous lumbar strain/sprain with evidence of fairly significant symptom magnification.

In a report to the employee’s attorney in April 2000, Dr. Frid stated the employee had chronic residuals from the 1999 injury with low back pain, muscular rigidity and stiffness, limitation of motion, and myofascial changes in the affected musculature.  He assigned a 10% permanency and stated the employee would benefit from occasional conservative management, as needed, during acute phases, as well as periodic medication for pain control.  Dr. Frid stated the employee’s work restrictions were permanent.  The doctor further observed the employee would remain predisposed to additional re-injury, as well as early and accelerated development of osteoarthritic and degenerative changes in the spine.  In an October 2000 letter, Dr. Frid maintained “the condition certainly could not be considered fully resolved.”  (Resp. Ex. 1.)

The employee was involved in a second non-work-related motor vehicle accident on August 29, 2000.  The employee returned to Dr. Frid on September 21, 2000, reporting worsening low back pain with generalized lower extremity weakness.  The doctor noted moderate to moderately severe paraspinal spasm, significantly decreased range of motion, and positive Kemp’s and straight leg raising tests with back pain.  Dr. Frid diagnosed an acute lumbosacral sprain/strain with possible lower extremity radiculopathy.  He prescribed physical therapy and chiropractic manipulation, and restricted the employee to a four hour day with no lifting over 40 to 50 pounds and limited bending and twisting.  The employee received chiropractic/physical therapy for the low back and occasional bilateral or right-sided radicular symptoms on a three day a week basis for a month.  On October 25, 2000, Dr. Frid released the employee to full-time work, eight hours a day, with no lifting over 50 pounds.

The employee continued to receive chiropractic/physical therapy from November through March 2001 on a reduced basis, with flare-ups and remissions, but some improvement.  A February 6, 2001, lumbar MRI scan showed degenerative disc changes at L1-2, L4-5 and L5-S1, including a diffuse disc bulge at L4-5 that contacted the left L4 nerve root with minimal posterior displacement, and a small to medium-sized central disc herniation at L5-S1 without displacement of the left S1 nerve root.  From and after April 2001, although he continued to have low back symptoms, the employee was managed with pain medications and as needed care.

On February 13, 2001, the employee was examined by Dr. Mark Gregerson, an orthopedic surgeon, at the request of the automobile insurer.  The employee reported primarily low back pain with radiating pain and tingling into the left leg to the ankle.  The employee stated his ongoing symptoms had not changed, overall, in the past three months and that chiropractic/physical therapy care provided only temporary relief.  Dr. Gregerson diagnosed a musculoligamentous lumbar strain and recommended an epidural steroid injection at L4-5, but no further medical care, and work restrictions for the next six months of no lifting over 30 pounds with limited repetitive or heavy lifting, bending and twisting.

The employee was seen by Dr. Bruce Idelkope for a neurological consultation and independent medical evaluation on August 8, 2001.  The employee complained of constant low back pain, aggravated by turning and twisting, with occasional radiating pain to the left buttock, thigh and calf.  Dr. Idelkope found no clinical evidence of neurological abnormalities indicative of spinal, nerve or rootlet injuries.

 From September 2001 through the fall of 2002, the employee’s medical records reflect ongoing, periodic treatment for his chronic lumbar back condition with intermittent lower extremity complaints (variously bilateral, left or right), including anti-inflammatory and pain medications, use of a lumbar brace, an epidural steroid injection, trigger point injections, and physical therapy and chiropractic care.  The employee was taken off work or had light-duty lifting restrictions on several occasions.

On October 10, 2002, the employee returned to Dr. Engel reporting low back pain and intermittent pain to his left foot.  The doctor prescribed medications and referred the employee for physical therapy.  The employee received chiropractic care and physical therapy three times a week throughout October then once a week through November 22, 2002, for an acute flare-up of his chronic lumbosacral sprain/strain injury with disc degeneration and radicular symptoms.  At his last visit, the employee reported feeling better but continued to have low back pain with restricted lumbar range of motion and tenderness on palpation in the lumbar paraspinals.

On January 30, 2003, the employee was seen at the Park Nicollet Clinic for low back pain, starting yesterday, lifting 80 pounds.  Michael Pischke, PAC, saw the employee and recorded a history of left low back pain occurring several hours after doing some lifting of blocks during work.  That same day, a First Report of Injury was completed reporting an injury on January 29, 2003, in the nature of lower back pain “walking up steps - lifting pail.”  (Resp. Ex. 9.)

On examination, Mr. Pischke noted the employee had minimal difficulty getting on and off the examination table and could ambulate quite well; had increased pain with flexion, rotation and extension; and pain in the lumbar paraspinous muscles and SI joint on deep palpation, but no muscle spasm.  There was no muscle weakness or paresthesias and lower extremity reflexes were equal and symmetrical.  Mr. Pischke diagnosed a lumbar sprain/strain, prescribed ibuprofen and Percocet, and referred the employee to physical therapy.  He released the employee to return to work with occasional lifting not over 20 pounds, no ladder climbing, squatting or kneeling, and no bending, twisting or reaching below knee level.

The employee was seen for physical therapy on January 31.  A history was recorded of “lifting 80# bag of cement up steps & tripped” with immediate pain in the left lumbosacral region.  (Pet. Ex. B.)  The employee returned to the Park Nicollet clinic for follow-up on February 13, at which time Mr. Pischke noted the employee was doing much better with only occasional lumbar region pain, mainly when bending and twisting.  Mr. Pischke related the employee did not find physical therapy helpful and discontinued it on his own.  Mr. Pischke stated the back examination was unremarkable, with some mild muscle spasm and diffuse tenderness over the upper right musculature, no radicular pain, muscle weakness or paresthesias, and an essentially normal neurological examination.  Light-duty restrictions were continued through February 20, including no lifting over 50 pounds and occasional bending and twisting.

On March 7, 2003, the employee sought treatment from Dr. Frid, giving a history of a low back injury on January 29 while lifting 80 pound bags of cement to the second floor of a customer’s home.  The employee reported mild improvement with treatment, but persistent severe low back pain with radicular lower extremity pain and numbness, right significantly greater than the left, and stated he was having significant difficulty performing his work duties, even light-duty.  Dr. Frid diagnosed an acute lumbosacral strain/sprain with lumbar disc syndrome and bilateral lower extremity radiculopathy, referred the employee for chiropractic care and physical therapy, and took the employee off work.  On March 11, the employee was seen by Dr. Engel for medications, reporting low back pain that spread to the right leg.  On examination, the doctor noted restricted, painful lumbar range of motion, reduced ankle jerks, and right-sided muscle spasms.  Dr. Engel diagnosed a lumbar sprain with mild degenerative changes, and recommended a repeat MRI scan and then an epidural block.

The March 12, 2003, MRI scan showed degenerative disc disease from L1-2 through L5-S1.  The radiologist noted a new, shallow right far lateral disc protrusion at L3-4, along with bulging discs at L4-5 and L5-S1, without evidence of stenosis or impingement.  In a follow-up evaluation on April 14, 2003, Dr. Frid noted the employee continued to experience spasms in the low back and radicular symptoms in the legs that were better some days than others.  The doctor’s assessment was ongoing acute lumbosacral strain/sprain with multiple level disc involvement, secondary to the work injury of January 29, 2003, superimposed on pre-existing lumbar disc disease.

The employee continued to receive regular chiropractic/physical therapy treatments through the month of June 2003, along with periodic evaluations by Dr. Frid and Dr. Engel.  The employee’s records reflect slow improvement with flare-ups and remissions of his low back pain.  Right leg complaints significantly diminished, but the employee then complained of intermittent bilateral and left or right leg symptoms.  In late May, the employee had a series of back injections, and on June 6, 2003, was given an epidural steroid block at L5-S1.  On June 30, 2003, Dr. Frid noted general improvement in the employee’s symptoms, with a persistent moderate decrease in range of motion and an essentially normal neurological examination.  The doctor released the employee to return to work on July 1, four hours per day, with light-duty restrictions of no lifting over 20 pounds and limited bending and twisting.

On June 22, 2003, the employee was seen by Dr. Edward Szalapski, an orthopedic surgeon, at the request of the employer and insurer.  An interpreter was present for the examination.  Dr. Szalapski recorded a history of an injury at a customer’s house on January 29:

In a report dated March 17, 2005, Dr. Frid stated the employee was under care at the clinic for a work-related injury sustained on January 29, 2003.  The doctor stated the employee’s condition was very mildly improved, but he continued to suffer from constant and severe low back pain and radicular lower extremity pain and numbness, right side significantly worse than the left.  Dr. Frid’s diagnostic impression was chronic residuals of a moderate lumbar strain/sprain; degenerative disc and joint disease of the lumbar spine; a new L3-4 right lateral disc herniation with compression of the right L3 nerve root; right lower extremity radiculopathy; and pre-existing disc protrusions at L4-5 and L5-S1 aggravated by the January 29, 2003, work incident.  Dr. Frid stated the employee’s current work restrictions included no lifting over 25 pounds; rated a 9% permanency for radicular syndromes, single vertebral level at L3-4; and opined the employee had reached maximum medical improvement as of that date. The employee continued to treat, as needed, on a periodic basis with Dr. Frid, Dr. Engel and other providers for low back pain and intermittent radiating leg pain through 2006.

In April 2003, the employee filed a claim petition alleging a work-related injury on January 29, 2003, and seeking various periods of temporary total and temporary partial disability benefits, permanent partial disability benefits and payment of disputed medical treatment and vocational rehabilitation expenses.  Following a hearing, the compensation judge, accepting the opinion of Dr. Szalapski, found the employee’s work activities on January 29, 2003, were not a substantial contributing factor in the employee’s subsequent low back and leg complaints, and that, to the extent the employee’s low back condition had worsened, it was the result of a natural progression of his pre-existing degenerative disc disease.  The judge, accordingly, denied the employee’s claims in their entirety.  The pro se employee appeals.

The employee asserts the compensation judge’s findings and his decision denying his claim for benefits are wrong and inequitable.  He contends the evidence does not support the judge’s determination and argues the judge misstated,^[4] misunderstood, misinterpreted or failed to properly credit evidence presented in the case.

The employee states the most important issue in the case was the nature of his injury following the January 29, 2003, incident.  He points to the new finding of a disc herniation at L3-4 in the March 12, 2003, MRI scan, and the fact that he returned to work with the employer following the motor vehicle accidents but was off work for an extended period of time after the January 2003 incident.  The employee argues the judge did not understand there was a new injury in January 2003, asserting his symptoms following the motor vehicle accidents were in a different place and were not comparable to the sharp pain he experienced after January 29, 2003.  The employee argues Dr. Szalapski’s opinion that his back condition was the result of the natural progression of his pre-existing degenerative disc disease is contrary to the 2003 MRI study.  He asserts that multiple treating doctors disagreed with Dr. Szalapski, who was hired by the insurance company, and contends the compensation judge had no basis for concluding that Dr. Szalapski’s opinion was more reliable than the opinions of Dr. Frid.  We are not persuaded.

In reviewing cases on appeal, this court is to determine only whether there is sufficient evidence of record to support the decision of the compensation judge.  It is not the role of this court to reconsider or reweigh the evidence.  Where the evidence is conflicting or more than one inference may reasonably be drawn from the evidence, the findings of the compensation judge must be upheld.  Redgate v. Sroga’s Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988), citing Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 37 W.C.D. 235 (Minn. 1984).  While there is evidence that would support the employee’s position, there is also evidence to the contrary.  Although the 2003 MRI study does include a new finding of a slight right-sided disc bulge at L3-4, the radiologist saw no evidence of stenosis or impingement, and there is little evidence in the medical records of any clinical correlation with the employee’s symptoms after January 2003 and this particular disc.  The employee’s symptoms both prior to and after the claimed injury included lumbar pain extending from the thoracolumbar junction to S1, with restricted motion and spasm, and non-focal, intermittent lower extremity symptoms.  And while Dr. Frid opined the employee had a new L3-4 disc herniation with compression of the right L3 nerve root and right leg radiculopathy, Dr. Engel’s diagnosis was very similar to that of Dr. Szalapski’s, that is, chronic lumbar pain with degenerative changes and mild radicular irritation involving the lower extremities.
 
The opinion of the employee’s treating doctor is entitled to no more medical credibility than the diagnosis of an independent medical examiner.  See, e.g., Wilson v. North Star Steel, slip op. (W.C.C.A. Dec. 7, 1993).  In this case, Dr. Szalapski concluded, after examining the employee and reviewing the employee’s very substantial medical records, that the employee’s ongoing low back problems were not related to the employee’s work activities on January 29, 2003, but were instead a manifestation of the employee’s long standing degenerative disc disease.  As the trier of fact, it is the compensation judge’s responsibility to weigh the evidence and resolve conflicting medical expert testimony.  The judge’s choice between medical experts will not be reversed by this court where there is sufficient foundation for the opinion.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73).  We conclude it was not unreasonable for the judge to infer from the employee’s medical records, and the opinion of Dr. Szalapski, that the employee was subject to a pre-existing degenerative low back condition that was not significantly aggravated by his work activities on January 29, 2003.

The employee also disagrees with the compensation’s judge’s finding that the medical records and the employee’s testimony reflect an element of symptom magnification, and argues the judge’s conclusion that the employee was not a reliable historian or credible witness is unjustified.  Assessment of witness credibility is the unique function of the trier of fact and this court must give deference to the compensation judge’s findings relating to credibility.  See Even v. Kraft, Inc., 445 N.W. 2d 831, 42 W.C.D. 220 (Minn. 1989); Tolzmann v. McCombs Knutson Assocs., 447 N.W. 2d 196, 42 W.C.D. 421 (Minn. 1989).  Given the long history and volume of the employee’s medical treatment for his low back, in combination with the employee’s limited English, we cannot say the compensation judge’s conclusion that the employee was not a reliable witness or historian is clearly erroneous.

Concluding the judge did not materially misstate or evidently misunderstand or misinterpret the facts in deciding this case, and that the judge’s decision is substantially supported by the record as a whole, we must affirm.