The employee appeals from the compensation judge’s determination that he did not sustain an injury to his spine, has no restrictions and was not disabled as a result of an incident at work on December 11, 2004.  We affirm.

Tony Dam, the employee, was working for Hi-Lo Manufacturing, the employer, on December 11, 2004.  On that date, the employee was involved in an altercation with his supervisor and a co-employee during the employee’s lunch break.  The employee did not return to work for the employer following the incident and his employment was terminated on December 14, 2004.

Following the altercation, the employee testified he “just felt a little bit of pain” and he went home.  (T. at 45.)  On December 15, 2004, the employee went to the St. John’s Hospital emergency room complaining of head pain.  The hospital records indicate the employee was accompanied by a friend who translated the employee’s native Vietnamese language to English.  A nurse’s note indicates the employee fell at work on December 11, 2004, and struck the back of his head while trying to break up a fight.  The employee complained of frontal head pain which radiated around his head.  Dr. Leidig examined the employee and noted he did not appear to be in any discomfort, although the employee stated he had the worst headache of his life.  A CT scan of the head was negative.  The diagnosis was a tension headache.  The employee was given an injection of Toradol and Vistaril in the right deltoid and was discharged.  The employee returned to St. John’s on December 18, 2004, complaining of ongoing headaches, intermittent dizziness and discoloration in the right upper arm in the area of the injections.  Dr. Workman examined the employee and noted his neck was supple and nontender and a motor and sensory examination was normal.  The doctor diagnosed a close-head injury with some headache and bruising at the injection site.  The doctor prescribed Darvocet and discharged the employee.

On December 18, 2004, the employee also sought treatment at Hynan Chiropractic Clinic for headache, neck pain and back pain.  The employee gave a history of breaking up a fight between his supervisor and a co-worker at which time he fell on the floor.  Dr. Hynan diagnosed an acute cervical strain with post-traumatic headaches and commenced a regimen of chiropractic treatment which continued until March 28, 2005.

On April 15, 2005, the employee sought a second opinion from Minh T. Pham, D.C., complaining of neck and low back pain.  The employee gave a history of falling and striking his head on the floor while trying to protect a co-worker who was attacked by a supervisor at work.  The doctor diagnosed cervical, thoracic and lumbar segmental dysfunction.  Dr. Pham commenced treatment which included spinal adjustments, mechanical traction and electrical stimulation.

The employee also saw Dr. Alfonso Morales on April 15, 2005, on referral from Dr. Pham.  The doctor diagnosed post-traumatic cervical, thoracic and lumbar strain and ordered cervical and lumbar MRI scans.  The cervical scan showed herniated discs at C3-4 and C5-6 with spurring and probable neck spasm as the result of the disc herniation.  The lumbar scan showed a herniated disc at L4-5 with mild to moderate central canal stenosis and a central bulge at L3-4.

Dr. Thomas Nelson, an orthopedic surgeon, examined the employee on April 19, 2005, at the request of the insurer.  Present with the employee was an interpreter.  Dr. Nelson obtained a history, reviewed the employee’s medical records, and conducted a physical examination.  The doctor stated the employee demonstrated no objective findings on physical examination.  The neurological examination was normal.  Dr. Nelson stated the employee’s diagnosis from the December 11, 2004, injury was a headache and a contusion to the left shoulder, both of which had resolved.  The doctor opined the employee was currently capable of employment without restrictions and opined the employee sustained no permanent disability.

Certain of the employee’s prior medical records were received in evidence at the hearing.  In May 1996, the employee was seen at St. Paul-Ramsey Medical Center complaining of back pain which he stated started about five years previously while he was in the Philippines in a refugee camp working and carrying heavy things.  The employee reported he then felt a crack in his spine and has had back pain ever since which comes on once or twice a month and gradually goes away.  The diagnosis was musculoskeletal pain and the doctor prescribed Ibuprofen.  By September 1996, the doctor noted the employee’s back pain had improved.  In November 1996, the employee was seen for panic attacks and headaches for which he was prescribed Xanax and Zoloft.  He was seen again in February 1997, with a history of chronic headaches and back pain and was diagnosed with multiple somatic complaints.  The employee was seen by a neurologist in April 1997, who diagnosed tension headaches.  (Resp. Ex. 12.)  In September 2001, the employee was seen at Regions Hospital complaining of a headache and mild dizziness.  The diagnosis was a panic disorder, headache and high blood pressure.  Medication was prescribed for a panic disorder and depression.  The employee returned to Regions periodically thereafter for medication follow-up.  The employee was seen on November 2, 2004, complaining of anxiety and depression due to conflict with a prior employer, Honeywell.  The diagnosis remained panic disorder and an adjustment disorder with a depressed mood.  On February 8, 2005, the employee gave a history of being fired from his job with the employer following an altercation at work.  The employee stated that he fell and hit his head on the floor, was seen in the emergency room and had a head CT scan which was normal.  The employee’s diagnosis was unchanged.  (Resp. Ex. 11.)

The employee filed a claim petition on January 6, 2005, seeking temporary total disability benefits, a rehabilitation consultation and payment of medical expenses.  Following a hearing, the compensation judge found the employee hit his head and shoulder on the floor in the December 11, 2004, altercation and sustained a shoulder contusion, a headache and a scrape on the leg.  The compensation judge found the employee did not sustain an injury to his spine in the altercation, had no restrictions and was not disabled as a result of the work injury.  The employee appeals.

The employee contends substantial evidence does not support the compensation judge’s decision that the employee did not sustain injuries to his neck and back on December 11, 2004.  While acknowledging the opinions of Dr. Nelson support the compensation judge’s findings, the employee contends Dr. Nelson’s opinions lack necessary foundation and the compensation judge erred in relying upon them.  The employee asserts Dr. Nelson’s opinions are either inconsistent or contrary to the facts in the following respects:

Foundation goes to the competency of a witness to provide an expert opinion.  The competency of a medical expert depends both on the extent of the scientific knowledge of the witness and “the witness’s practical experience with the matter which is a subject of the offered testimony.”  Reinhardt v. Colton, 337 N.W.2d 88, 93 (Minn. 1983).  Sufficient knowledge of the subject matter can be obtained by personal knowledge, a hypothetical question or testimony at the hearing.  Scott v. Southview Chevrolet Co., 267 N.W.2d 185, 30 W.C.D. 426 (Minn. 1978).  Dr. Nelson obtained a history from the employee through an interpreter, reviewed the relevant medical records and performed a physical examination.  We have repeatedly held this level of knowledge is sufficient to afford foundation for the opinion of a medical expert.  See, e.g. Caizzo v. McDonald’s, 65 W.C.D. 378 (W.C.C.A. 2005).

As the employee correctly notes, there are inconsistencies in Dr. Nelson’s report.  Although the doctor correctly states treatment at Hynan Chiropractic Clinic commenced on December 18, 2004, Dr. Nelson does not explain why he found the treatment at Hynan Chiropractic from December 20 through January 3, 2005, to be reasonable and necessary since during that time the employee received treatment for his neck and low back.  Such concerns, however, call into question neither the degree of the doctor’s knowledge or the extent of his experience.  Although these concerns may relate to the persuasiveness or weight afforded the medical opinion of Dr. Nelson, they are insufficient to establish a lack of foundation.  See, e.g. Drews v. Kohl’s, 55 W.C.D. 33 (W.C.C.A. 1996).  Dr. Nelson stated the employee had no objective findings on physical examination and unequivocally opined the employee did not injure his neck or back on December 11, 2004.  This opinion was adequately founded and the compensation judge could rely upon it.

In his memorandum, the compensation judge explained he did not find the employee’s testimony credible, stating there were “numerous instances were [sic] his testimony or statements made to others appeared to be inaccurate or untrue.”  (Memo. at p. 4.)  The employee argues this is inadequate in the absence of any description of the testimony or statements which the compensation judge perceived as inaccurate or untrue, citing Bromen v. White Motors, Inc., 42 W.C.D. 708 (W.C.C.A. 1989), sum. aff’d. (Minn. 1989), the employee argues absent specific factual findings on the issue of credibility the Workers’ Compensation Court of Appeals cannot effectively review the compensation judge’s decision.  Accordingly, the employee contends the case should be remanded to the compensation judge for further factual findings.  We are not persuaded.

Assessment of the credibility of a witness is the unique function of the trier of fact.  Brennan v. Joseph G. Brennan, M.D., P.A., 425 N.W.2d 837, 839-40, 41 W.C.D. 79, 82 (Minn. 1988).  A finding based on the credibility of a witness will not be disturbed on appeal unless there is clear evidence to the contrary.  See Even v. Kraft, Inc., 445 N.W.2d 831, 835, 42 W.C.D. 220, 225-26 (Minn. 1989).  Further, this court must give “due weight to the opportunity of the compensation judge to evaluate the credibility of witnesses appearing before the compensation judge.”  But a finding regarding credibility of a witness like any other factual finding must be supported by substantial evidence.  The substantial evidence standard “is an admonition to the reviewing court not to treat the findings of the fact finder lightly, while at the same time the reviewing court remains cognizant of its own responsibility to exercise good judgment in reviewing what the evidence will reasonably sustain.”  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 239 (Minn. 1984).

The employee denied any back problems prior to working at Hi-Lo Manufacturing.  Records from the St. Paul-Ramsey Medical Center prior to 2004, however, reflect chronic complaints of headaches and back pain.  (Resp. Ex. 12.)  The employee contends he injured his neck and low back on December 11, 2004, but the St. John’s Hospital emergency room records for December 15 and December 18, 2004, do not reflect any complaints of neck or back pain.  The employee contends it is likely the examining physician simply failed to provide a fully-detailed account of all of the employee’s complaints.  Further, the employee was accompanied to the emergency room by his minor son who acted as his interpreter.  Certainly, the compensation judge could have concluded, as the employee argues, the absence of neck and back complaints in the emergency room records was due to a failure of communication caused by a language barrier.  The compensation judge, however, apparently chose not to make this inference and certainly a less favorable explanation could also be reasonably inferred.

Given the facts in this case, we cannot conclude the compensation judge’s determination that the employee’s testimony lacked credibility was unsupported by substantial evidence.  Further, the medical opinions of Dr. Nelson support the compensation judge’s findings and those findings must, therefore, be affirmed.