The employee appeals from the compensation judge’s decision that claimed medical treatment and surgery was not causally related to or reasonably necessary to cure and relieve the effects of the employee’s low back injury of February 4, 1999.  We affirm.

On February 4, 1999, the employee was working as a daycare aide for the employer, Lil Rascals Daycare.  While standing up after tying a child’s shoe, the employee reacted to an object apparently thrown by another child and which was flying at her face.  She instinctively leaned backwards and twisted her body to avoid being struck.  She immediately felt an onset of back pain, which worsened as the day progressed, and began to radiate down her legs.

The employee testified that she had previously received chiropractic care for low back problems beginning about 1982, when she was treated for a low back sprain several times a month for about three or four months.  She testified that she then continued to receive chiropractic “maintenance” treatments monthly until about 1993, but she did not treat with a chiropractor again until after the 1999 work incident.^[1]

Following the 1999 incident, the employee initially sought chiropractic treatment from Dr. David S. Russoff, who referred her to Dr. Seth Rosenbaum at ORC Neck and Back Specialists for evaluation, although he continued to provide chiropractic treatment.  Dr. Rosenbaum first saw the employee on February 8, 1999.  Her symptoms on that date included mid to low back muscle spasm and pain, along with pain and paresthesias radiating down the left leg to the foot and down the right to the upper calf.  Dr. Rosenbaum suspected disc herniation, and referred the employee for an MRI scan.

The MRI scan was performed on February 9, 1999.  It showed mild degenerative disc disease at L4-5 and L3-4 with left lateral annular tears and moderate dehydration of the L3-4 and L4-5 discs.  There was no evidence of disc herniation or bony stenosis and no indication of any nerve root encroachment.  The scan also showed that the employee had partial congenital sacralization of the L5 vertebrae on the right.

When the employee was seen by Dr. Rosenbaum on February 12, following the scan, the doctor noted that the MRI abnormalities did not account for the employee’s sensory changes.  He speculated that a part of the employee’s pain pattern might be accounted for on the basis of a myofascial injury.  On February 19, 1999, Dr. Rosenbaum stated that the mechanics of the reported injury were somewhat unusual.  He speculated that perhaps an overstretch injury in the sacroiliac and iliolumbar areas might have been caused as the result of excessive torque about the pelvis which combined with the employee’s preexisting congenital lower spinal malformation.  Dr. Rosenbaum recommended that the employee continue with intensive chiropractic treatment, which he considered appropriate based on the MRI findings.  He released the employee to return to work part-time hours with restrictions.

On April 2, 1999, the employee was still having substantial ongoing problems and symptoms, though she had experienced some improvement with chiropractic care.  Myofascial trigger points were noted in the left lumbar paraspinal and left gluteus minimus which produced radiating pain down the posterolateral leg and the biceps femoris.  Dr. Rosenbaum thought that the employee likely had sustained injury to two areas, the first consisting of some disk damage bulging as recorded on the MRI scan, and the other consisting of a torsion injury of the pelvis at the symphysis pubis and left sacroiliac joints, with over stretch to some of the nerves, which was starting to resolve.  He recommended that she continue with chiropractic treatment.

On April 23, 1999, Dr. Rosenbaum recorded a small interim improvement in the employee’s condition.  He recommended piriformis stretching exercises.  By May 7, the employee was noted somewhat improved and was tolerating her return to work at three hours per day.  Dr. Rosenbaum scheduled her for MedX testing to evaluate muscular strength and for consideration of additional exercises to add to her regimen.

The employee also started treatment with the Noran Clinic by self-referral beginning on May 12, 1999.  A radiologist there reviewed the employee’s prior MRI and concluded that the findings were consistent with mild degenerative disc disease at L3-4 and L4-5.

The employee was examined, apparently for the employer and insurer, by orthopedist Dr. William Akins on May 21, 1999.  The employee’s complaints were of constant pain in the lumbosacral area radiating into the left buttock, posterior aspect of the left thigh and plantar aspect of the left foot.  Her neurologic exam was objectively intact.  Dr. Akins noted that the employee was a smoker and smoked a pack of cigarettes a day.  He considered the employee’s symptoms consistent with nerve root irritation secondary to secretion of chemicals from her damaged discs at L3-4 and L4-5.  He opined that in cases of annular tears, physical therapy treatment other than stretching was of no benefit, and in the majority of cases reduction or elimination of the patient’s pain would occur with the passage of time, typically within about 8 months.  Because of this, he considered continuing work restrictions against repetitive bending, stooping or lifting more than ten pounds were currently justified, although he saw no objective medical basis why the employee could not work full time.  He related the employee’s treatment and restrictions to the work injury but did not consider chiropractic care effective, and recommended it be discontinued.  He recommended that the employee undergo an epidural steroid injection.  If this did not produce significant clinical improvement, then he thought that the employee would then have reached maximum medical improvement.

On May 24, 1999, Dr. Rosenbaum recommended continued chiropractic treatment once a week.  He noted there had been a small improvement in the employee’s condition and he increased her work hours to four per day, with a 15 pound lifting limit.  The employee was treated several times over the next two months, having experienced an exacerbation of symptoms after reaching down to pick something up.  By June 24, 1999, her symptoms were back to the pre-exacerbation baseline.  Dr. Rosenbaum referred the employee for an epidural steroid injection at the L4-5 level.

A left L4-5 epidural steroid injection was performed on July 1, 1999.  Following the epidural injection, the employee had no improvement in her overall condition.  On August 27, 1999, Dr. Rosenbaum recommended a sacroiliac joint injection.

On September 22, 1999, the employee returned to the Noran Clinic where she was seen by Dr. Richard Golden.  He noted that the employee’s back pain and neck pain had not changed despite treatment.  He found significant spasm in the left paralumbar region accompanied by a limited range of motion.  Dr. Golden agreed with the suggestion for an injection into the sacroiliac joint and also suggested alternative therapies including massage, myofascial release, and biofeedback.

A left sacroiliac joint injection was performed on October 1, 1999.  On October 14, Dr. Rosenbaum noted that the sacroiliac joint injection appeared to aggravate rather than relieve the employee’s symptoms.  He referred the employee to Dr. Manuel Pinto at the Twin Cities Spine Center for surgical evaluation.

The employee was also seen for consultation on October 26, 1999, at Physicians Neck and Back Clinic by Dr. Joseph Wegner.  Dr. Wegner recommended a short term active rehabilitation program.  He also thought that the employee should be screened for possible depression.  By December 7, the employee had undergone ten treatments at the clinic.  She was seen as having made only equivocal effort in the program and had experienced only slight improvement.  She was released to return to full-time work.

On December 14, 1999, the employee was evaluated by psychologist Jerry Gregersen, Ph.D.  She was diagnosed with major depression and chronic pain.

Dr. Pinto saw the employee on January 6, 2000.  She continued to experience low back and left leg pain.  It was noted that the employee was a smoker who averaged one pack of cigarettes per day for the past 18 years.  She currently was working four and a half hours a day as a daycare aide.  Examination revealed a slight limp without antalgia, minimal midline back tenderness, and tenderness at the sacroiliac joints and the L5-S1 region.  There was a slight decrease in sensation in the left L5-S1 distribution, and straight leg raising reproduced the shooting sensations down the employee’s left leg.  Dr. Pinto thought the employee had discogenic pain, and suggested that the employee consider a lumbar discogram to assist in determining the source of her symptoms.

Discography was performed at multiple levels on February 3, 2000.  Concordant pain was produced at the L4-5 and L3-4 levels.  Her pain at L2-3 was not concordant and the attempt to inject L5-S1 was unsuccessful.  On February 24, 2000, the employee returned to Dr. Pinto for review of the discogram.  The doctor noted leakage of contrast material at L3-4 and L4-5 with concordant pain.  He considered the employee a reasonable candidate for fusion surgery at L3-4 and L4-5, but suggested she should only consider surgery if she could not otherwise cope with her pain.

The employee was seen on April 19, 2000, by Dr. Lon Lutz, a pain management specialist at Medical Advanced Pain Specialists (MAPS).  Dr. Lutz suggested that the employee consider an IDET procedure as an alternative to fusion surgery.  The employee decided to try this, and on July 13, 2000, the employee underwent a two level IDET procedure with rhizotomy at the L3-4 and L4-5 levels.

On August 2, 2000, the employee reported to Dr. Lutz that her pain level was about what it was prior to the procedure.  Over the next several months, the employee was followed by Dr. Lutz on several occasions and noted no significant change in her symptoms.  On December 4, 2000, Dr. Lutz noted that the discography previously done at L5-S1 was not able to evaluate whether the employee’s disc at that level was symptomatic.  He suggested that discography be repeated at this level.  A discogram at L5-S1 on January 8, 2001, was read as giving concordant pain.  Dr. Lutz suggested that the employee try a further IDET procedure at this level.

The employee underwent the IDET procedure at the L5-S1 level on February 27, 2001.  On March 13, 2001, Dr. Lutz noted that following the L5-S1 procedure the employee continued to experience low back pain radiating into the left buttock and leg.  Her care over the next several months was largely directed by Dr. Espeland, a pain management specialist.

In May, 2001 the employee told Dr. Espeland that she had recently been doing reasonably well, but had recently fallen and was having persistent axial back pain with problems standing, walking, and sitting.  She was advised to limit her activity and avoid bending and lifting.

The employee was evaluated for physical therapy at the Institute for Athletic Medicine on June 14, 2001, and was questioned regarding her progress after the latest IDET procedure.  She reported that her symptoms had been improving until an incident in April.  Her complaints were of numbness in the left foot and a shooting pain off and on in the left leg which had started after the IDET procedure.  She did not report any other symptoms.

On July 17, 2001, the employee was seen in follow-up by Dr. Espeland.  She had noted increased flexibility with physical therapy and thought her symptoms had improved about 15 percent overall since the IDET procedure.

In October 2001 the employee was seen by Dr. Lutz and was still complaining of low back pain radiating into her legs.  Dr. Lutz’s diagnosis was of lumbar degenerative disc disease with refractory low back pain.  He recommended that the employee return to see Dr. Pinto.

Dr. Pinto saw the employee on January 3, 2002.  The employee’s most significant pain was in her left leg, rather than in her low back as it had been when he had seen her previously.  He noted that the employee had not had relief from her IDET procedures.  Dr. Pinto suggested that the employee could undergo an anterior-posterior lumbar fusion, in which case he recommended that she first have a repeat MRI scan.  If she did not wish to proceed to surgery, he suggested that she remain active, continue physical therapy, and undergo pool therapy.

The employee elected not to proceed to surgery.  By this time she was working part time as a food service worker for the Farmington High School.  In July 2002, both Dr. Pinto and Dr. Lutz concluded that the employee had reached maximum medical improvement, and both provided a permanent partial disability rating of 10 percent.

When Dr. Espeland saw the employee on October 4, 2002, he noted that she was doing “fairly well.”  She was enjoying her part time work in the school cafeteria, though her back would become sore by the end of her workday.  Dr. Espeland recommended that she continue taking Vicodin as needed and return for a recheck in three months.

On January 31, 2003, Dr. Espeland indicated that the employee was reporting greater pain that day which she associated with having twisted her back the day before “while putting something away in the cupboard.”  She was advised to return in about three to four months.

The employee was next seen for a recheck for her back in June 2003.  She had been laid off for the summer in her cafeteria job.  The employee reported problems in her left knee and her right eye and an injury to her face while helping her husband with boards on a deck.  She was again advised to return in about three to four months.

The employee returned to Dr. Espeland on August 29, 2003, because of a flare up in her left leg pain which she thought might be related to stress and the weather.  This flare up had not yet abated when she was seen again on October 1, 2003.  The employee told Dr. Espeland that she was still working for the school system in their food service department and was stooping to wash down tables, as well as mopping, sweeping, and lifting more than 10 pounds.  Dr. Espeland recommended an updated MRI and clarified the employee’s work restrictions.

An MRI of the lumbar spine was performed on October 3, 2003.  It was read as showing multilevel disc degeneration and dehydration.  Dehydration and disc bulging were reported at the L2-3, L3-4, and L4-5 levels but with no evidence of nerve compression.

The employee was referred for a consultation with Dr. John Dowdle, an orthopedic spine specialist, who saw the employee on January 7, 2004.  The employee was noted able to go from sitting to standing without discomfort, and could stand on her heels and toes.  Straight leg raising was negative.  There was tenderness in the low back with flexion and extension.  Dr. Dowdle diagnosed mechanical low back pain with disc degeneration at L4-5.  He recommended that the employee continue to use a low back support.  He placed her on light duty restrictions with no more than 20 pounds lifting, no repetitive bending, and recommended she return in one month.

On February 10, 2004, the employee returned to Dr. Dowdle.  She continued to have persistent leg pain.  A Medrol Dosepack was prescribed, but this did not substantially improve the employee’s symptoms by February 17, when Dr. Dowdle noted that she was still having “mechanical back pain.”  He referred her to Physicians Neck and Back Clinic (PNBC) for an active exercise program.

The intake notes from PNBC indicate that the employee’s leg symptoms were considered to be referred pain rather than radicular in nature.  By May 12, 2004, the employee had participated in 15 treatment sessions at PNBC.  Her back and leg pain had improved and her back was stronger.  She was released to full time work five days a week with less restrictive 25-30 pound lifting restrictions.  The employee was still having mild numbness in the left leg but had significant improvement in other subjective symptoms.  PNBC recommendations included discontinuing formal rehabilitation and transitioning to a home exercise program using a Roman chair and Swiss ball.  Her discharge diagnosis was mechanical low back pain, lumbar degenerative disc changes by imaging, and deconditioning syndrome.  PNBC physician Dr. Mark Rotty opined that she had reached maximum medical improvement (MMI ) as of May 12, 2004, and he found no change in the permanent partial disability rating.

On May 18, 2004, Dr. Dowdle saw the employee noting that she had done well and improved overall.  There was still some tenderness in the low back, depending on her movement and activities, but back pain was improved.  Dr. Dowdle agreed that the employee had reached MMI.  He did not anticipate a need for further care and treatment but provided prescriptions for Vioxx and Ultracet.

Dr. Dowdle rechecked the employee on August 17, 2004.  He noted that she continued to do well.  There was mild tenderness in her low back but the doctor thought this was likely associated with a recent abdominal surgery.  He advised the employee to show caution in bending and lifting.  He did not recommend further treatment and suggested the employee reduce her medication to an as-needed basis.

The employee did not seek any medical treatment for low back or leg symptoms during the next several years, until March 2008 when she was seen at Allina Medical Clinic in Farmington by Dr. Leo Avenido for lower back pain radiating to both legs, with some left leg numbness and toe numbness in the right foot.  The record notes a duration of two days.

The employee was eventually referred for an MRI and a consultation with Dr. Pinto.  On May 27, 2008, an MRI of the employee’s lumbar spine was done.  It showed disc degeneration at L2-3, L3-4, L4-5, and L5-S1.  There were annular disc bulges at L2-3, L3-4, L4-5, and L5-S1 without evidence of nerve compression.  High intensity zone annular tears were present at L2-3 and L3-4.

The employee returned to Dr. Pinto on June 26, 2008.  Dr. Pinto recorded that the employee had persistent low back, left buttock and left lower extremity pain in the distribution of the L5 nerve root.  He recommended a brace and discussed possible surgery, though he considered that a last resort in cases of multilevel lumbar disc disease.

On August 28, 2008, the employee returned to Dr. Pinto to discuss treatment options.  Dr. Pinto gave her the choice to continue conservative care or proceed to surgery.  The employee felt she had exhausted conservative care and was interested in the surgery.  Dr. Pinto referred the employee for discograms from L1 to the sacrum to determine which discs were involved in her pain syndrome.

On September 11, 2008, a six-level discography was performed at CDI by radiologist Kurt Schellhas.  The discogram showed abnormal morphology at all levels except for L2-3, and concordant pain was produced at L3-4, L4-5, L5-S1, and S1-2.

In a letter dated September 19, 2008, Dr. Avenido wrote that the employee had chronic recurring back pain and a history of spine surgery.  He opined that recent symptoms of back pain could be related to her low back work injury, given that there was no report of a new trauma or injury when she came in to him for treatment on March 6.

The insurer refused to pay the medical bills associated with the employee’s 2008 treatments, and the employee filed a medical request on September 24, 2008, seeking reimbursement for the charges of the Allina Clinic and the Twin City Spine Center.  The employer and insurer filed a medical response noting that several years had elapsed since the employee had reached MMI and completed prior treatment, and disputing a causal connection between the recent treatment and the work injury.

On November 19, 2008, an administrative conference was held on the medical request.  A decision was issued on December 1, 2008, ordering payment of the medical bills then outstanding.  The employer and insurer challenged the order and filed a request for formal hearing on December 12, 2008.

The employee was seen by Dr. Pinto on January 8, 2009, to review her discography results.  Dr. Pinto diagnosed a symptomatic lumbar disc derangement at multiple levels.  He noted that the employee had undergone extensive conservative treatment but had continued to have pain for about ten years.  Dr. Pinto and the employee discussed a four-level fusion done through a combined anterior/posterior approach.  The employee decided to proceed to surgery, if possible, and was referred for an updated MRI scan.

The MRI, done on January 24, 2009, showed disc dessication at L2-3 to L5-S1, with slight annular bulging at L2-3 and L3-4.  There was no evidence of herniation, neural compression, or significant stenosis.  Left facet joint hypertrophy was present at L4-5.  The disc space at L5-S1 was again noted to be transitional.  The scan was compared with the prior MRI done in 2003.  This showed a progression of disc space narrowing and dessication at L5-S1, but no appreciable changes from L2-3 to L4-5.

On February 23, 2009, the employee was seen on behalf of the employer and insurer by Dr. Charles V. Burton.  Her chief complaint was of low back pain radiating into the left leg.  She described the leg pain as “variable” with occasional radiation to the foot.  The employee was noted to have an odor of tobacco about her and acknowledged having been a smoker for 20 years, currently at “under a pack a day.”  She exhibited guarding and a limited range of motion associated with verbal pain behavior.  There was diffuse tenderness throughout the lower lumbar spine and more prominent tenderness in the paravertebral area to the sacrum.  Palpation of the left sciatic notch referred pain into the left foot.  The employee’s range of motion was limited in extension and lateral flexion.  The hips did not show restriction in adduction and abduction.  There was no edema or atrophy in the lower extremities, and strength and reflexes were normal and symmetric.  Hypoesthesia was present to pin testing in an L5-S1 pattern.  Straight leg raising and Patrick’s test were negative.

Dr. Burton noted that the imaging studies had shown multilevel degenerative changes throughout the lumbar spine but no evidence of nerve compression.  He characterized the employee’s complaints as largely subjective in nature and without objective neurologic findings or physical impairments.  He felt that she exhibited a “classic chronic pain syndrome associated with pain perception unassociated with objective neurologic impairment.”  In his view, the 1999 work injury had been one of many incidents which had aggravated a long-standing and pre-existing multilevel degenerative disc disease.  The work injury had reached maximum medical improvement by August 2004, and was no longer causally related to the employee’s current symptoms or proposed surgery.  Dr. Burton opined further that the surgery being proposed was neither reasonable or necessary, both because of the lack of objective findings to support the recommendation, and because of the risk factors associated with the employee’s positive history for depression and 20-year history as a smoker.

Dr. Pinto saw the employee on February 26, 2009, for review of the MRI.  The employee was offered an anterior fusion at L3-4, L4-5, L5-S1, and S1-2, along with posterior spine reconstruction from L3 to S2.  She wished to proceed with the surgery.

At a pre-trial conference on the medical request in April 2009, the parties informed the judge that the employee had incurred further medical expenses since the date of the administrative order, and that surgery was currently also proposed and was disputed.  The judge ordered a continuance of the hearing to facilitate expansion of the issues to include the more recent treatment and proposed surgery.

In a letter dated May 26, 2009, to the employee’s attorney, Dr. Pinto opined that the work injury was a cause of the employee’s current condition and need for treatment, stating that “if [she] did not have any significant back pain prior to the injury at work, [and] then with the injury at work her symptoms started and have remained severe for all of these years, then I believe it is reasonable to state that the work injury was a significant contributing factor toward the patient’s back pain.”  The proposed surgery was justified on the grounds that the employee had exhausted conservative care and on the basis of statistics cited by Dr. Pinto suggesting that the majority of patients in multilevel fusions achieve a 50 percent pain improvement in their preoperative pain.

On July 15, 2009, the employee underwent the proposed surgery.

The employer and insurer asked Dr. Burton to review the medical records since his examination and to comment on Dr. Pinto’s opinions.  In a letter dated July 31, 2009, Dr. Burton strongly reiterated his disagreement with Dr. Pinto over the causal nexus between the work injury and the employee’s current condition, the reasonableness and necessity of the multilevel surgery given the employee’s risk factors, the absence of clear objective indications, and the merely subjective nature of her pain complaints.  In his opinion, the surgery greatly increased the potential for degeneration of the spinal level above the fusion.  He cited statistical evidence from a study which suggested that such multilevel surgery was correlated with an overwhelmingly high risk of total disability as the eventual outcome.

The matter was heard before a compensation judge of the Office of Administrative Hearings on August 8, 2009.  Following the hearing, the judge found that the care and treatment provided in 2008 and 2009, including the four-level fusion performed on July 15, 2009, was not causally related to or reasonable and necessary to cure and relieve the effects of the employee’s February 4, 1999, low back injury.  The employee appeals.

When an appeal is taken from a compensation judge’s factual findings, this court’s review is limited to deciding whether the judge’s findings and order are “clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted.”  Minn. Stat. § 176.421, subd. 1(3) (1992).  If the judge’s findings of fact are not clearly erroneous, and are supported by substantial evidence, we must affirm.  This court is not a finder of fact, and on appeal the court will not “retry” the factual issues which were before the lower court; thus, it doe not matter if different findings than those made by the compensation judge could also have been reached on the same evidence.  Substantial evidence supports the findings if, in the context of the record as a whole, 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 the evidence conflicts, or more than one inference may reasonably be drawn from the evidence, the judge’s findings must be affirmed.  Id. at 60, 37 W.C.D. at 240.  Similarly, factual findings are clearly erroneous only if “the reviewing court on the entire evidence is left with a definite and firm conviction that a mistake has been committed.”  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229, N.W.2d 521, 524 (1975).  Factual findings may not be disturbed, even though this court might disagree with them, “unless they are clearly erroneous in the sense that they are manifestly contrary to the weight of evidence or not reasonably supported by the evidence as a whole.”  Id.

This case presented two very different medical opinions.  Dr. Burton, who examined the employee for the employer and insurer, was of the opinion that the employee’s recent increased low back and leg pain was the result of degenerative disc disease of long standing, rather than being due to the work injury.  Dr. Burton also was of the opinion that a multi-level fusion was not reasonable or necessary treatment.

Dr. Pinto, who had seen the employee for surgical consultations in 2000 and 2002, and more recently since 2008, is the surgeon who recommended and performed the multi-level fusion and, obviously, considered it reasonable and necessary treatment.  He offered the opinion that if the employee’s symptoms started followed the 1999 work injury, and had remained severe from that time to the present, the 1999 work injury would be a substantial contributing factor to the current symptoms and need for treatment.  Dr. Avenido, who saw the employee on March 6, 2008, also thought that the employee’s recent exacerbation of symptoms of back pain could still be related to her low back work injury, given that there was no report of a new trauma or injury when she came in to him for treatment.

The compensation judge adopted the opinion of Dr. Burton, finding that opinion to be more persuasive than the opinions of Dr. Pinto and Dr. Avenido.  It is the role of the compensation judge, as the finder of fact, to make the choice between competing medical opinions.  See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  Unless the opinion relied upon by the compensation judge did not have an adequate factual foundation, this court generally will affirm the judge’s findings where based on that choice.  See, e.g., Smith v. Quebecor Printing, Inc., 63 W.C.D. 566, 573 (W.C.C.A. 2003).

The objection raised by the employee to the foundation for Dr. Burton’s opinions is her contention that he was mistaken about whether she was a “chronic smoker,” as he characterized her in his July 31, 2009, letter opinion.  She points to her testimony that she smoked less than a pack a day during the 20 years preceding the date of her surgery, which she contends made her a “casual smoker.”  We note, however, that the term “chronic” refers to duration rather than intensity.  A chronic smoking habit is one which has lasted for years, regardless of the number of cigarettes smoked per day.  A 20 year smoking habit certainly is one of prolonged, or “chronic” duration.  Nor does it appear that Dr. Burton was mistaken about the employee’s smoking habits.  In his IME report dated February 23, 2009, he specifically notes that the employee smoked "less than a pack a day."  Finally, we note that the issue of the extent of the employee’s smoking was not, as she suggests, part of the basis for the doctor’s opinion that the 1999 work injury was not a causal factor in the employee’s recent worsened symptoms and renewed need for treatment, although it did contribute to his appraisal of the reasonableness of multi-level fusion surgery, in that the doctor noted that smokers have a far lower rate of successful surgical fusion than nonsmokers.

Dr. Burton’s reports outline the information on which he based his opinions, including history received from the employee, a physical examination, and a quite extensive review of the medical records.  It thus appears evident that he had adequate foundation to render a medical opinion in this matter.

The employee contends, however, that the compensation judge should have given the opinion of Dr. Pinto greater weight than that of Dr. Burton, citing the specifics of Dr. Pinto’s qualifications and his experience.  We note, however, that Dr. Burton’s qualifications also to render an expert opinion are not in question.  An expert’s degree of expertise is one, but not the only, factor to consider in determining how much weight to give a medical opinion.  It is within the compensation judge’s discretion to assess the weight and sufficiency of a medical expert’s opinion.  Ruether v. State, Mankato State Univ., 455 N.W.2d 475, 477, 42 W.C.D. 1118, 1121 (Minn. 1990) 455 N.W.2d at 477.  Here, we cannot say that the compensation judge’s choice of Dr. Burton’s opinion was a clear abuse of that discretion.

The employee points to various aspects of the evidence that support her contention that the 1999 work injury remained a cause of her current symptoms.  We concede that the evidence might also have permitted a contrary result in this case, but under the scope of factual review allowed to this court, the question before us is only whether there was substantial evidence to support the findings the judge actually made.  Where more than one inference may reasonably be drawn from the evidence, the findings of the compensation judge are to be upheld.  Redgate v. Sroga’s Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).

Among other evidence supporting the judge’s findings, the employee acknowledged that she had received more than a decade of ongoing chiropractic treatment for low back symptoms between 1982 and 1993, before the 1999 work injury.  Shortly after the work injury, radiologic studies showed that extensive degenerative disc disease was already present at multiple levels of the low back.  The employee’s symptoms after the 1999 injury undeniably increased, and remained intractable over several years of treatment, but by 2004 she was reporting significant improvement and her physicians discharged her from further treatment.  She was apparently able to function without any medical treatment after that until 2008, when she experienced what she reported as a new exacerbation of symptoms of recent duration.  It was this recent exacerbation that prompted and required the current treatment and it is this recent exacerbation for which causation was at issue.

This evidence is consistent with Dr. Burton’s opinion and with the compensation judge’s apparent conclusion that symptoms from the employee’s degenerative disc disease had already been present prior to the 1999 work injury, that the exacerbation of those symptoms caused by the work injury had resolved sufficiently by 2004, and that the employee was no longer in need of further treatment for the effects of that injury.  It was Dr. Burton’s opinion that the recent exacerbation of the employee’s symptoms resulted not from a continuation of the effects of the work injury, but from deterioration in her underlying degenerative disc disease.  The compensation judge’s adoption of that opinion was not unreasonable and we must affirm.

We note, also, that the causation opinion of Dr. Pinto was expressly based on the absence of low back problems prior to 1999, and on the premise that the symptoms after the 1999 work injury continued severe and unabated.  While we acknowledge that the employee testified that she had no prior symptoms like those after 1999 and that her symptoms did not diminish very much between 2004 and 2008, the compensation judge was not required to fully accept that testimony, where contrary conclusions might reasonably be drawn from the medical records.  As such, the opinion of Dr. Pinto on causation was not consistent with the facts and inferences as determined by the compensation judge, and it was therefore reasonable for the compensation judge to find that opinion less than compelling.  The compensation judge, in her memorandum, also provides insight into why she rejected Dr. Avenido’s opinion on causation, and we cannot conclude that in doing so she abused her discretion.

The judge also found that the treatment rendered from and after 2008 was not reasonable or necessary to cure and relieve the 1999 work injury.  This finding, in part, follows naturally from the finding that the newly worsened symptoms for which treatment was rendered were not causally related to that injury.  The employee’s argument on this issue is essentially to restate Dr. Pinto’s opinion as definitive.  We note, however, that here, as in the matter of causation, the compensation judge was entitled to adopt the opinion of Dr. Burton.

Because substantial evidence, including well-founded expert medical opinion, supported the compensation judge’s findings, we must affirm.