The employee appeals from the compensation judge’s denial of his claim for temporary total disability benefits as well as certain medical and rehabilitation expenses.  We affirm.

Jose Lara was employed by Mavo Systems when he sustained a work injury to his low back on September 21, 2011.  He began working as a laborer for Mavo Systems in January 2004.  Mavo’s business was asbestos abatement and the employee’s job was to remove walls, ceilings, and carpeting as a part of that process.  He used a 20- to 30-pound sledge hammer to knock down walls and ceilings, and used wheelbarrows and carts to remove the debris.

On September 21, 2011, the employee and a coworker were moving a cart filled with building material.  At one point, they had to lift the cart, weighing between 180 and 200 pounds, over an obstacle and when they put the cart down, Mr. Lara felt what he described as a crack in his back.  He had immediate pain in his low back and left leg.

Mr. Lara went to urgent care at the Olmstead Medical Center Clinic for his low back pain on September 23, 2011.  He was given pain medication and released to sedentary work.  He then returned to Olmstead Medical Center Clinic on September 28 and treated there, receiving conservative care in the form of medication, activity restrictions, and physical therapy.  An MRI was done on November 23, 2011, and was read as showing disc herniation at L5-S1 with disc extrusion impinging on the L5 and S1 nerve roots.  The employee was then referred to Mayo Clinic Spine Center for further care.

Mr. Lara saw Dr. Bradford Currier, an orthopedic surgeon at Mayo, on December 12, 2011.  Dr. Currier provided treatment options of oral steroids, epidural steroid injections, or surgery, and the employee opted for surgery.  On December 15, Dr. Currier performed an L5-S1 hemilaminotomy and discectomy.

After his surgery, Mr. Lara began treating with Dr. Russell Gelfman at Mayo Clinic Work Rehabilitation Center.  At the employee’s first visit on January 16, 2012, it was noted that his left leg pain was “considerably better,” but he still had low back pain at 5 on a 10-point scale.  Dr. Gelfman recommended physical and occupational therapy and restricted Mr. Lara to four-hour work shifts with occasional lifting of 10 pounds or less.  Mr. Lara returned to work for Mavo on January 23, 2012, on light duty and began receiving temporary partial disability benefits from the insurer.

On January 27, 2012, after two physical therapy sessions, the employee was reporting pain at 1 or 2 out of 10, and he described “mild low back pain.”  On January 31, Mr. Lara told the physical therapist his pain was at 1 on the 10-point scale.  On February 2, the physical therapist noted “patient rates his current pain as a 0 in the low back. . . .  No low back pain after last session.”  On February 8, Mr. Lara rated his pain as 0, and the same report regarding low back pain was made at visits on February 8, 10, and 14.

The employee saw Dr. Gelfman on February 14, 2012.  It was noted that in physical therapy, Mr. Lara has progressed “to a 50-pound lift and reports no pain on today’s visit.”  Mr. Lara was no longer taking any medication, and his “current pain” was recorded as being 0/10.  Dr. Gelfman released the employee to return to work without restrictions.

Mr. Lara returned to work at Mavo at his regular job.  He subsequently reported another incident that he alleged took place on March 13, 2012, when he was swinging a sledge hammer against a wall and developed pain in his neck, back, and legs.

The employee returned to Dr. Gelfman on March 20 and related this incident.  He reported that after the incident, his back hurt more, his left leg started to feel cold, his left leg seemed weaker than his right, and his back pain was worse with coughing and sneezing.  He was on crutches when he saw Dr. Gelfman.  The physical examination was essentially normal except for tenderness to palpation in the lumbar spine.  Dr. Gelfman took the employee off work.

A repeat MRI was done March 21, and was interpreted as showing “only postoperative changes with no recurrent disc herniation.”  When Mr. Lara saw Dr. Gelfman on March 21, he reported “discomfort radiating up toward his neck on the left side, as well as paresthesias in both legs.”  The employee was using crutches.  Dr. Gelfman recommended a return to physical therapy and also prescribed pain medications.  Physical therapy was not helpful in alleviating Mr. Lara’s symptoms.  At physical therapy sessions on April 16 and 18, he reported pain at 10/10 in both his low back and neck.  When Dr. Gelfman saw the employee on April 24, he stated, “I am at a loss to explain his severe functional limitations.”  A referral was made to Dr. Currier, who found no basis for any further surgical treatment.  Mr. Lara also saw Dr. James Watson at the Mayo Clinic Pain Clinic on June 25, 2012, for possible treatment options.  The employee did not return to the Mayo Clinic after that date except for an emergency room visit in September 2012 for his low back pain.

Mr. Lara transferred his care to the Noran Neurological Clinic and saw Dr. Fred Lux on June 11, 2012.^[1]  Dr. Lux outlined a number of possible diagnoses and recommended an epidural steroid injection, increased medication, and keeping Mr. Lara off work.  A cervical MRI was done on June 20 and was read as showing mild to moderate multilevel degenerative disc disease with mild posterior bulging at C6-7.  Dr. Lux saw the employee again on July 10, and apparently agreed with Dr. Watson that a pain clinic approach would be appropriate.  Mr. Lara testified he did not proceed with further treatment after that time because the workers’ compensation insurer would not pay for any additional medical treatment.

Mr. Lara was seen by Dr. William Simonet on July 16, 2012, at the request of the employer and insurer.  Dr. Simonet reviewed medical records relating to the employee’s treatment for his work injury and conducted a physical examination.  Dr. Simonet characterized the examination as normal except for what he described pain behavior by Mr. Lara.  Dr. Simonet’s impression was of “somatoform pain behavior (psychogenic pain), physical symptoms without organic pathology to explain” and “symptom amplification for secondary gain.”  Dr. Simonet concluded Mr. Lara needed no work restrictions since, “he has nothing physically wrong with him.”  No further treatment was necessary in Dr. Simonet’s opinion.

Dr. Lux provided a medical report dated September 14, 2012 to Mr. Lara’s attorney.  Dr. Lux stated, “In my opinion he has sustained an injury that affects his lumbosacral spine with radicular type symptoms affecting his left leg and L5-S1.”  Dr. Lux further stated that the employee should have pain clinic treatment and should not work.

The parties filed a number of pleadings which were consolidated and heard by Compensation Judge James Cannon on October 15, 2012.  The compensation judge identified the issues for determination as being the employee’s entitlement to temporary total disability benefits after August 18, 2012, payment of medical expenses at Mayo and MAPS, and the employee’s entitlement to rehabilitation services.  The compensation judge issued his findings and order on January 3, 2013.

The compensation judge determined that the employee did not sustain a work injury to his back or neck on March 13, 2012, and adopted Dr. Simonet’s opinion that the employee needed no physical restrictions or medical treatment.  The compensation judge denied the claim for temporary total disability benefits, allowed rehabilitation services up to the date of discontinuance, August 18, 2012, and medical expenses up through the date of Dr. Currier’s exam on May 14, 2012.  The employee has appealed.

The employee argues on appeal that the compensation judge’s decision is not supported by substantial evidence.  He contends that he never fully recovered from the effects of the September 2011 injury and that his condition was aggravated by his injury in March 2012.  As a result, the employee claims he is unable to work and is in need of additional medical care so that he may return to employment.

The employee’s claims rested primarily on his testimony.  To the extent that the testimony conflicted with the medical records, the employee argued at the hearing, as he does on appeal, that his testimony should control.  Unfortunately for this argument, the compensation judge made a specific finding that “based on the court’s observation and demeanor of the employee during his testimony, it is determined that the employee was not a credible witness regarding his alleged symptoms and disability.”  (Finding 20; emphasis in the original.)

“The assessment of witnesses’ credibility is the unique function of the trier of fact.”  Michaels v. ADM Milling Co., 68 W.C.D. 253, 257 (W.C.C.A. 2008).  We have noted that our deference to the compensation judge in making a credibility determination is based on the compensation judge’s ability to view witnesses and their demeanor during direct testimony and cross examination.  May v. Delta Air Lines, Inc., 72 W.C.D. 767 (W.C.C.A. 2012).  Here, based on his determination that the employee was not credible, the compensation judge concluded the employee did not sustain a work injury on March 13, 2012.

The compensation judge also specifically adopted the opinion of Dr. Simonet in reaching his conclusions.  Dr. Simonet concluded that the employee was not suffering from the effects of a work injury, did not need any work restrictions, and did not require any medical care of any type.  The employee argues, however, that Dr. Simonet’s opinion actually supports his position.  According to this argument, since Dr. Simonet diagnosed the employee with somatoform pain behavior, his opinion is consistent with the opinions of Dr. Lux and Dr. Gelfman that Mr. Lara has chronic pain as a result of his work injury.  This is a mischaracterization of Dr. Simonet’s opinion.

Dr. Simonet does not at any place in his report state that the employee has chronic pain related to his work injury.  He does not even diagnose somatoform pain disorder, but rather uses the phrase somatoform pain behavior and couples that with his additional impression of “symptom amplification for secondary gain purposes.”  Further, Dr. Simonet added in his report, “I would not place any restrictions on Mr. Lara at this time.  He has nothing physically wrong with him.  To restrict a patient such as this only serves to reinforce his perception of injury and disability which frankly does not exist.”  We conclude that a reading of Dr. Simonet’s report makes it completely clear that he does not agree with a medical opinion that the employee should have restrictions or treatment related to his work injury.

Dr. Simonet reviewed medical records concerning Mr. Lara’s treatment.  He took a history and conducted a physical examination.  He had sufficient information to establish foundation for a medical opinion.  Scott v. Southview Chevrolet, 267 N.W.2d 185, 30 W.C.D. 426 (Minn. 1978).  This court will generally affirm the decision of a compensation judge based on the choice between expert opinions unless the facts assumed by the expert in reaching his opinion are not supported by the evidence.  Smith v. Quebecor, 63 W.C.D. 566 (W.C.C.A. 2003); Perry v. ADB Construc. Inc., 68 W.C.D. 491 (W.C.C.A. 2008).

The compensation judge’s decision is affirmed.