The employer and insurer appeal the compensation judge’s finding that the employee’s work injuries were substantial contributing factors to the employee’s low back condition.  We affirm.

Cheryl Beck, the employee, sustained two work-related low back injuries while working as a head cashier for Lowe’s Home Centers, Inc., the employer, which was insured for workers’ compensation liability by New Hampshire Insurance Company, administered by Sedgwick Claims Management Services, Inc.  The injuries occurred on September 5, 2008, when the employee was helping a customer lift a “heavy”^[1] gas grill onto a trailer, and on February 21, 2011, when she slipped on ice and fell in the employer’s parking lot.

The employee had sought medical treatment for low back symptoms in the past.  In May 2001, she treated with Dr. Steven Voss at Allina Medical Clinic for low back pain, which was not work-related, and was off work for a few days. She treated for low back pain again in September 2001 and for neck pain, headaches, and low back pain in December 2003.  The employee treated for these conditions again in 2004.  In 2005, the employee experienced right hip pain.  Dr. Voss diagnosed right trochanteric bursitis and treated the employee with cortisone injections in July 2005, December 2005, and February 2006.  The employee was also referred for physical therapy, and a surgical consultation was considered for the right hip in April 2006.

At the time of her 2008 work injury, the employee was working without restrictions and could perform her job without assistance.  On September 5, 2008, the employee injured her low back while helping a customer load a grill on a trailer.  The employee sought treatment a few days later with Dr. Voss who diagnosed lumbar strain and possible chest wall strain, prescribed medication, and placed the employee on work restrictions.  The employee reported worsening symptoms, including radicular right leg pain, in October 2008.  X-rays indicated disc space narrowing at L4-5.  An October 20, 2008, lumbar spine MRI scan indicated degenerative disc disease at L3 to L5, a disc bulge at L3-4 contacting the right nerve root with mild central canal narrowing, and a right annular tear and mild annular bulge at L4-5 with mild bilateral foraminal narrowing.  Dr. Voss diagnosed low back pain with radicular symptoms likely related to L3-4 disc herniation with right L3 nerve root impingement and referred the employee for a lumbar epidural steroid injection.  In November 2008, the employee experienced an increase in low back pain after bending forward to pull a package off a cart.  Dr. Voss diagnosed probable ligamentous strain and L3-4 disc herniation with nerve irritation.  Another lumbar epidural injection was recommended, which provided limited relief.

In January 2009, Dr. Voss referred the employee for physical therapy and for a surgical consultation with Dr. Paul Hartleben.  Dr. Hartleben also recommended physical therapy, which the employee attended at Physicians Diagnostic and Rehabilitation Center.  In August 2009, the employee reported some improvement but still had low back pain.  Dr. Voss recommended yoga exercises.  In September 2009, the employee also reported low back pain, and Dr. Voss advised continued physical therapy.  The employee experienced a low back pain flare up in January 2010.  In May 2010, the employee reported increased symptoms after driving a long distance.  Dr. Voss treated the employee with trigger point injections.  In June 2010, she reported worsening symptoms after working nine days in a row.  She was treated again with trigger point injections at that time and in July, August, and September 2010.  In January 2011, the employee exacerbated her chronic low back pain while mopping at work.  Dr. Voss treated her with medication, referred her for physical therapy, and restricted her from mopping.  The employee continued working but gave up some physical recreational activities because they increased her pain.

On February 21, 2011, the employee fell in the employer’s parking lot while walking to her car after work.  She was seen by Dr. Voss on February 25, 2011, for increased left neck and shoulder pain, left low back pain with burning into her hip, and headache.  Dr. Voss diagnosed left lumbar strain and sprain, left neck strain and sprain, and migraine headache.  He referred the employee for chiropractic treatment and continued the employee’s medications and work restrictions.  The employee received chiropractic treatment with Dr. Richard Ottomeyer and physical therapy.  Dr. Ottomeyer referred the employee for a neurological consultation with Dr. George Adams, who recommended continued conservative care and avoiding heavy repetitive lifting.  The employee continued treating with Dr. Voss throughout 2011.

At the request of the employer and insurer, the employee underwent an independent medical examination with Dr. Rajan Jhanjee on June 1, 2011.  Dr. Jhanjee concluded that the employee had sustained a musculoligamentous strain of the cervical and lumbosacral spine and a head contusion at the time of her February 2011 work injury.  He opined that the employee had reached maximum medical improvement, needed no further treatment, had no permanent partial disability, and could work without restrictions.  Dr. Jhanjee also stated that the employee’s medical treatment and diagnostic tests to that point were reasonable, necessary, and causally related to the work injury.  Dr. Voss disagreed with Dr. Jhanjee’s opinion that the employee could work without restrictions and recommended a functional capacity evaluation.

In November 2011, Dr. Voss referred the employee for a lumbar spine epidural injection.  The employee experienced some relief for three to four days.  In March 2012, Dr. Voss assessed an exacerbation of the employee’s low back pain.  Dr. Voss referred the employee to the Midwest Spine Center where she was evaluated by Dr. Stephen Knuff.  Dr. Knuff recommended epidural steroid injections and medication.  On April 30, 2012, the employee underwent left L3-4 and L4-5 transforaminal epidural steroid injections.  The employee experienced some relief.

In August 2012, Dr. Jhanjee reviewed additional medical records and concluded that the employee’s MRI findings pre-existed her work injury and that the employee’s musculoligamentous strain was superimposed on the employee’s pre-existing degenerative condition.  He indicated that the February 2011 injury possibly aggravated the employee’s pre-existing arthritis but was not a substantial contributing cause of her current disability and need for treatment.  While he agreed that the employee could remain on work restrictions, he opined that these restrictions were related to the employee’s underlying lumbosacral spine condition.

The same month, Dr. Voss referred the employee for L3 and L4 perineural cortisone injections, which provided some relief.  The employee reported worsening neck and low back symptoms to Dr. Voss in December 2012.  Dr. Voss referred the employee for physical therapy in January 2013.  X-rays taken at that time indicated advanced L4-5 disc degeneration and mild to moderate L3-4 disc degeneration.  Dr. Voss noted that the employee had no significant improvement from physical therapy in April 2013, and recommended home exercise and medication.  The employee had also developed urinary incontinence.  A May 2013 lumbar spine MRI scan indicated severe degenerative disc changes at L3-4 and L4-5, and a bulging disc at L4-5 contacting both L5 nerve roots, and a bulging disc at L3-4 with dorsal tear and herniation displacing both L4 nerve roots.

The employee was referred to Dr. Thomas Reiser at Midwest Spine Clinic for a surgical consultation in June 2013.  Dr. Reiser recommended an SI joint injection.  In July 2013, the employee treated with Dr. Voss for severe low back pain with radiculopathy.  Dr. Voss took the employee off work pending a subsequent evaluation with Dr. Reiser.  Dr. Reiser noted that the employee had little relief from the injection, and recommended a discography.  The employee continued to have ongoing symptoms and pain.  An August 19, 2013, discography indicated discogenic pain at L3-4 and L4-5.  On August 30, 2013, Dr. Reiser recommended an anterior/posterior fusion at L3-4 and L4-5, possible iliac crest bone graft, and possible decompression.

On August 5, 2013, the employee filed a claim petition seeking temporary total disability benefits and approval of various medical treatment recommendations.  In their answer, the employer and insurer admitted the employee had sustained work injuries on September 5, 2008, and February 21, 2011, but denied the nature and extent of the injuries, the dates of temporary disability, and the relationship between the medical treatment requested and the admitted work injuries.  On October 10, 2013, the employee underwent another independent medical examination with Dr. Jhanjee.  Dr. Jahnjee filed a supplemental report concluding, in part, that the employee’s September 2008 sprain/strain injury was an aggravation of the employee’s underlying degenerative low back condition and that the employee’s work injuries were not substantial contributing factors to her current disability and need for medical treatment.  He further opined that the changes indicated in the employee’s lumbar spine MRI scan were of a chronic degenerative spondylotic nature, and that the employee’s need for treatment and work restrictions were not related to the work injuries.  The employee underwent an anterior posterior fusion surgery at L3-4 and L4-5 on October 15, 2013.

At a hearing on December 11, 2013, the parties stipulated that the employee’s wage loss was causally related to her low back condition and that her claimed medical treatment was reasonable, necessary, and causally related to her low back condition.  The remaining issue at the hearing was whether the employee’s work injuries were substantial contributing factors to her low back condition.  The employee testified under oath at the hearing.  In a findings and order issued on January 10, 2014, the compensation judge found that the employee’s work injuries were substantial contributing factors of her low back condition, and awarded medical expenses and wage loss benefits.  The employer and insurer appeal.

The Workers’ Compensation Court of Appeals will uphold the factual findings of the compensation judge if they are supported by substantial evidence and were reached through application of the correct legal standard.^[2]  Substantial evidence is such relevant evidence as a reasonable mind might accept as adequate to support a conclusion.^[3]  In reviewing for substantial evidence to support the judge’s findings, we do not make credibility determinations.^[4]  Where oral evidence in the record could allow reasonable minds to differ as to whether the employee’s low back condition and need for treatment are causally related to the employee’s work injuries, the responsibility for that decision rests with the compensation judge.^[5]  With this standard of review in mind, we consider the employer and insurer’s argument that the record lacks substantial evidence to support the compensation judge’s findings that the low back condition and need for fusion surgery are causally related to the work injuries.

The employer and insurer argue that the record lacks substantial evidence to support the compensation judge’s finding that the employee’s disability is causally related to the employee’s September 5, 2008, and February 21, 2011, work injuries.  Questions of medical causation fall squarely within the province of the compensation judge.^[6]  A work injury is compensable if the employment is a substantial contributing factor to the aggravation or acceleration of a pre-existing condition.^[7]  An employee need not prove that the employment was the sole cause, only a substantial contributing cause of the disability for which benefits are sought.^[8]  In the present case, the award of benefits was based on the treatment records and the testimony of the employee.

Specifically, the employer and insurer point to the fact that no expert medical opinion was given on causation to support the judge’s determination and ultimate finding that the employee’s low back condition and need for fusion surgery are causally related to the work injuries.  The compensation judge noted in her memorandum that there is no expert causation opinion directly supporting the employee’s claim in the record.  When there is other reliable evidence in the record to support the compensation judge’s findings, a finding of causation will not ordinarily be disturbed on appeal, even in the absence of supporting expert medical opinion.^[9]  In this case, we note there are no unusual complicating factors which require a specific medical causation opinion.^[10]  Further, the employee’s treating doctors accepted that the employee’s work activities caused her condition.

The compensation judge explained in her memorandum that she reached her finding on causation based on the employee’s medical treatment records, the employee’s testimony, and the lack of symptoms, medical treatment, or work restrictions associated with her low back between December 15, 2004, and September 5, 2008.  The judge concluded from the evidence that “the work injuries permanently aggravated/accelerated the employee’s pre-existing, but asymptomatic, degenerative disc disease.”^[11]  She noted that the treatment records document a dramatic change in the employee’s low back condition after each of the work injuries that never returned to a pre-September 2008 level.  The employee’s testimony regarding her injury and the onset of her symptoms in relation to the work injuries was accepted by the compensation judge.  The compensation judge also noted that “[t]he timing of the onset of symptoms in relation to the work injuries and their unrelenting nature strongly suggest the injuries at issue caused a permanent change in the employee’s low back that led to the recent fusion surgery.”^[12]  This explanation provides the basis on which the judge inferred that the employee’s reports to her doctors, in conjunction with her testimony at hearing, were an accurate reflection of the onset of her condition and were sufficient to establish causation.  While there was no one specific piece of evidence to explain the connection between the condition and the work injury, there were a number of facts in evidence which allowed the compensation judge to infer an explanation for the cause of the condition and ultimately reach a conclusion on the condition as a work-related disability.  Substantial evidence supports the compensation judge’s findings that the low back condition and need for fusion surgery are causally related to the work injuries.

The employer and insurer also argue that the compensation judge erred by not considering all of their evidence, specifically by failing to reference Dr. Jahnjee’s opinion.  Dr. Jahnjee opined that the employee’s work injuries were not related to her current low back condition and need for surgery.  While a compensation judge may not ignore or “disregard” an uncontroverted medical opinion,^[13] “there is a difference between disregarding [an] unopposed medical opinion and rejecting it on the basis of other evidence.”^[14]  Such “unopposed” testimony is not necessarily conclusive upon the trier of fact.^[15]  To that end, the compensation judge is not required to discuss every piece of evidence introduced at the hearing.^[16]  The compensation judge’s findings and memorandum sufficiently show the judge’s reasoning and provide an adequate basis for this court to review the disputed issue.^[17]  The judge did not err by failing to mention Dr. Jahnjee’s opinion in her findings and order.  We affirm.