The employee appeals from the compensation judge’s finding that chiropractic treatment rendered from July 10, 2004, to August 3, 2005, was not reasonable or necessary for the treatment of the employee’s March 8, 2004, work injury.  We affirm.

The employer, Instant Web Companies, is a printer and direct mailer of consumer mail offers.  David Bond, the employee, began working for the employer in April 1995.  He was employed as a maintenance mechanic, with his primary duties consisting of the repair and maintenance of printing presses and other equipment.  He also performed other tasks as needed including snow removal and moving barrels of waste printing solvents and inks.

After a work injury to the right upper arm in 1996, the employee began receiving chiropractic treatment with Paul W. Lemke, D.C.  Dr. Lemke also treated the employee in 1998 for upper back and neck pain following a non work motor vehicle accident.

On September 28, 2002, the employee slipped on oil at work and fell, after which he experienced the onset of low back pain with pain radiating into the groin bilaterally.  He started treatment for his injury on September 30, 2002, with Dr. Lemke, who diagnosed a thoraco-lumbar strain/sprain, multilevel thoracic and lumbar subluxations, and right sacroiliac subluxation.  During October 2002, the employee treated with Dr. Lemke about three times per week for his symptoms, which consisted of right-sided hip pain, low and mid-back pain, and buttock and flank pain.  By November 2002, the employee was again working ten to 12 hour days per week for the employer in his regular duties.  He continued treating with Dr. Lemke twice a week through December 2002 and January 2003.  As of the beginning of February 2003, Dr. Lemke had reduced treatment to one visit per week.

The employee sustained a reinjury at work on February 15, 2003, when he slipped on water and fell.  On February 17, 2003, Dr. Lemke noted that the employee’s symptoms now included right-sided neck pain, mid back pain, shoulder pain, and lower back pain.  He diagnosed cervical, thoracic and lumbar strain, myofascial pain syndrome, rotator cuff strain, lumbar disc syndrome and multilevel subluxation.  He restricted the employee to work only eight hours per day for the next six days.  The employee treated with Dr. Lemke about three times per week during the remainder of February, March and April.  An MRI of the employee’s lumbar spine was performed on March 11, 2003.  The MRI showed lumbar disc dehydration at L2-3 and mild disc bulging at L3-4 with no stenosis, disc compression or herniation.  An epidural injection was performed on April 10, 2003.  By the end of April, the employee’s chiropractic treatment was reduced to two visits per week and his work hours were expanded to allow 10 hours a day.

In mid-May, 2003, the employee had elevated lower back, hip and buttock pain, with pain into the left leg, and Dr. Lemke recommended that the employee see Dr. Ronald M. Tarrell, D.O., for a neurological consultation at the Noran Clinic.  On Sunday, May 25, 2003, the employee saw Dr. Lemke for an emergency chiropractic visit.  He told the doctor he had experienced sharp, searing pain in his low back on bending forward.  The employee returned the next day for another emergency chiropractic treatment, noting continued elevated low back pain with radiation into the right hip and knee and around the groin area.  The employee treated with Dr. Lemke eight times over the next eleven days and as of June 6, 2003, was reporting a substantial overall reduction in pain, particularly in the low back, hip and leg.

On June 9, 2003, the employee was seen by Dr. Tarrell.  The employee’s neurological exam was negative, but Dr. Tarrell noted a marked decrease in the range of motion throughout the lumbar spine.  Given the employee’s radicular symptoms, Dr. Tarrell suggested repeating the epidural injection and performing a CT and myelogram.  The CT was performed on June 12, 2003, and showed minimal bulging at three lumbar levels with no evidence of acute herniation, nerve root impingement, or spinal stenosis.  The findings were read as consistent with mild diffuse lateral spondylosis.

By June 24, 2003, Dr. Lemke’s records indicate that the employee had experienced significant relief.  He was released to return for further treatment on an as needed basis.  The employee thereafter treated with Dr. Lemke about once a week through August 2003, and then at about two to three times per month through February 2004, for various combinations of low, mid and upper back pain, shoulder pain, neck pain, hip and right leg pain and headache, which he often attributed to working long hours or to specific heavy work activities.

On March 8, 2004, the employee fell at work when he stepped onto a piece of cardboard that had oil under it.  He landed on his right hip, right shoulder, and right elbow, and struck his head.  The employee was sent to see Dr. Evgeny Tseplaev, a medical doctor at the Ridgeview Chanhassen Clinic.  Dr. Tseplaev diagnosed a lumbosacral and cervical strain with concussion.  He took the employee off work, prescribed Advil and Flexeril, and advised the employee to return in one week for reevaluation.

The employee also saw Dr. Lemke the same day.  Dr. Lemke diagnosed a cervical/thoracic sprain/strain, a lumbosacral sprain/strain, rotator cuff strain, hip strain, myofascial pain syndrome, and subluxation at multiple areas.

The employee saw Dr. Lemke for chiropractic treatment daily for that week, and returned to Dr. Tseplaev on March 15, 2004.  He told Dr. Tseplaev that he had not started the Flexeril, but had instead treated with his chiropractor.  His low back pain and headache had improved but he still had neck and shoulder pain.  Dr. Tseplaev noted that the employee’s upper extremity numbness and tingling followed a left C8 distribution.  He diagnosed a cervical strain with some signs of radiculopathy.  He kept the employee off work for another week, and suggested a head and neck clinic, but the employee elected to continue chiropractic treatment instead.

The employee continued daily treatments with Dr. Lemke through March 20, 2004, after which he was scheduled for treatment on a three day per week basis.  On March 22, Dr. Lemke outlined return to work restrictions consisting of limiting lifting to 10 pounds, and of avoiding bending, twisting or reaching.  The employee was authorized to return to work initially at four hours per day, to increase after two weeks.  That same day, the employee saw Dr. Tseplaev, who agreed with the return to work limitations and deferred further treatment to Dr. Lemke.

The employee returned to work on a four hour per day basis on March 24, 2004.  During April, he slowly continued to improve.  His work restrictions were raised to six hours per day with 20 pounds carrying.  His symptoms varied but overall he had significant improvement to his low back and hip pain by mid April, and a cervical pillow, provided in late April, brought him a significant decrease in neck pain and headache.  From mid-April through May he continued to receive chiropractic treatment at about three times per week.  On May 5, he was released to work eight hours per day, with lifting at 25 pounds.

On April 14, 2004, Dr. Lemke opined that the employee had reached MMI from his earlier, 2002 and 2003 work injuries on January 31, 2004, with a 13.5 percent permanent partial disability.

Dr. Lemke reduced the employee’s treatment schedule to twice a week on May 12, 2004.  On May 14, the employee reported elevated headache, neck and shoulder pain.  He returned for an unscheduled appointment the next day, but over the next three appointments his pain decreased.  However, on May 28, the employee came in for two chiropractic visits the same day, seeking treatment for a severe increase in his neck and upper back pain.  Dr. Lemke recommended that the employee undergo a cervical MRI scan.

The MRI was performed on June 4, 2004.  It showed a small, broad-based central and right-sided disc herniation at C6-7, but without cord or nerve root impingement.  The employee treated with Dr. Lemke about twice a week over the next month.  The doctor’s charts notes in this period show the employee complaining of varying degrees of headache, neck, upper back, right shoulder, and low back pain and stiffness, but generally indicate continuing improvement.  On June 19, Dr. Lemke noted that he anticipated treatment could be reduced to one visit per week in about three weeks.

On July 9, 2004, the employee was examined by chiropractor John M. Wildenauer, on behalf of the employer and insurer.  The employee noted complaints of low back soreness, a sore and stiff neck, and headaches.  Examination showed no spasm or nodules along the cervical, thoracic or lumbar spine, although the employee expressed tenderness to cervical palpation.  Spinal range of motion was unimpaired and neurological testing was normal.  Dr. Wildenauer concluded that the March 2004, work injury had resulted in a soft tissue aggravation of the cervical, thoracic, and lumbar spine, and the sacral, hip and right shoulder regions, as well as a concussion with a recurrent headache.  He opined that these had resolved, and that the March 8, 2004 work injury had been a temporary aggravation to the employee’s prior condition and was no longer a substantial factor in his current complaints.  In his opinion, the employee needed no restrictions and no further chiropractic care was medically necessary after May 8, 2004.

In accordance with Dr. Wildenauer’s opinion, the employer and insurer disputed payment for further chiropractic treatment after July 9, 2004.

The employee saw Dr. Lemke the next day, Saturday, July 10, 2004, reporting that Dr. Wildenauer’s examination had irritated his neck and shoulder.  The doctor reduced the treatment schedule to one visit per week, and then, on July 24, 2004, to a per needed basis.  The employee testified that, since that date, he has determined when to see Dr. Lemke, based on how much pain he has.  He takes ibuprofen at work and uses ice and heat at home, but when this does not take care of his pain he returns to see Dr. Lemke.

From July 2004, through September 2005, the employee saw Dr. Lemke variously from two to five times per month, averaging a little less than once per week.  According to his testimony, Dr. Lemke’s treatments have been needed to keep his pain level sufficiently reduced to permit him to perform his job duties, which are strenuous and which, from time to time, exacerbate his symptoms.

The issue of the reasonableness and necessity of chiropractic treatment after July 9, 2004, was heard before a compensation judge of the Office of Administrative Hearings on September 9, 2005.  Following the hearing, the judge found that the treatment in dispute was not reasonable or necessary.  The employee appeals.

At issue before the compensation judge was the reasonableness, necessity, and causal relationship of the chiropractic treatments the employee received from Dr. Lemke between July 10, 2004, and August 3, 2005.  The judge denied reimbursements for the treatments, concluding that the employee had not proved that the treatment was reasonable and necessary.

The employee argues on appeal that the compensation judge applied an improper legal standard, requiring the employee to show significant improvement, complete independence from treatment, and that treatment was close-ended, as a legal prerequisite to a finding that the treatment was reasonable and necessary.

Minn. Stat. § 176.135 requires the employer to provide such medical care “as may reasonably be required at the time of the injury and any time thereafter to cure and relieve from the effects of the injury.”  Included under the statute is palliative care to prevent pain and discomfort even though the treatment cannot effect a cure.  Castle v. City of Stillwater, 235 Minn. 502, 51 N.W.2d 370, 17 W.C.D. 103 (1952).  An employee has the burden of proving that his or her claimed medical expenses were reasonable, necessary, and causally related to his or her work injury.  See, e.g., Adkins v. University Health Care Ctr., 405 N.W.2d 233, 39 W.C.D. 898 (Minn. 1987).  The determination of whether particular services rendered by a chiropractor were reasonably required to cure and relieve the employee from the effects of the injury is a factual one to be made by the compensation judge.

Considerations which may be relevant in determining whether chiropractic services are reasonably required include: evidence of a reasonable treatment plan, documentation of the details of the treatment, the degree and duration of relief resulting from the treatment, whether the frequency of treatment is warranted, the relationship of the treatment to the goal of returning the employee to suitable employment, potential aggravation of underlying conditions, duration of treatment, and cost.  Field-Seifert v. Goodhue County, slip op. (W.C.C.A. Mar. 5, 1990).  Other relevant factors include: the employee's testimony concerning the relief obtained; the possibility that other conditions not discovered by the chiropractor may be causing the employee's symptoms; whether treatment is scheduled on a regular or an as needed basis; the use of other health care providers in the event of continuing symptoms; the employee's overall activities and the extent of the employee's ability to work; and the employee's dependence on the treatment.  Horst v. Perkins Restaurant, 45 W.C.D. 9 (W.C.C.A. 1991), summarily aff'd (Minn. July 10, 1991).  "The appropriate factors will vary from case to case, depending upon the unique circumstances of each situation."  Fuller v. Naegele/Shivers Trading, slip op. at 4 (W.C.C.A. Apr. 14, 1993).

In the present case, the compensation judge found that the employee’s symptoms, although fluctuating, have continued without any significant objective or subjective improvement despite the ongoing and extensive chiropractic treatment.  The judge further noted that Dr. Lemke has nonetheless not modified his treatment plan or recommended cessation of treatment during the roughly 14 months of treatment.  In addition, the judge found, in essence, that the treatment notes reflect that the employee, who has continued to average almost one chiropractic visit per week, displays a dependence on ongoing chiropractic treatments.  Finally, in her memorandum, the compensation judge noted that she did not find persuasive the employee’s testimony that the treatment was needed to assist him in continuing to work with the employer.  The determination of witness credibility is a matter generally left to the sound discretion of the compensation judge and here cannot be said to be so contrary to the other evidence in the case as to merit reversal.  See, e.g., Even v. Kraft, Inc., 445 N.W.2d 831, 42 W.C.D. 220 (Minn. 1989).

All of the foregoing are factors which the compensation judge might legitimately consider in evaluating the reasonableness and necessity of the chiropractic treatment.  While it would have been error for the compensation judge to have treated these factors as legal prerequisites to a finding of compensability of the treatment, rather than as factors to consider in weighing the evidence as a whole, we see nothing in the opinion which would indicate that this was done.  Rather, it appears to us that the compensation judge highlighted these factors as those given the most weight in her consideration of the entirety of the evidence.

The compensation judge’s conclusions were also supported by the expert opinion of Dr. Wildenauer denying the necessity of the treatment for the period in question.  While the compensation judge did reject that portion of Dr. Wildenauer’s opinion which considered the employee’s March 2004 work injury wholly temporary in nature, she was not thereby prevented from accepting that portion of the doctor’s opinion bearing on whether the employee’s condition needed continuing chiropractic treatment, which was based on the doctor’s assessment of the employee’s condition as of the date of the examination.  It is the role of the compensation judge to resolve any differences or conflicts between the medical experts.  Generally, this court must uphold findings where primarily based on a compensation judge’s choice between conflicting expert opinion, unless the facts assumed by the expert on whom the judge relies are not supported by the evidence.  Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).