The self-insured employer appeals from the compensation judge’s award of prescription medication expenses.  We affirm.

On January 31, 1979, the employee sustained a work-related injury to his low back while employed by The University of Minnesota [the employer], which was self-insured for workers’ compensation purposes.  The employee testified that he had continued intermittent low back pain after this injury, but he remained employed and avoided surgery until February of 2000, when he underwent a three-level anterior/posterior lumbar fusion procedure, with hardware, performed by Dr. Glenn Buttermann.  After commencement of litigation, the parties entered into a stipulation for settlement, wherein the employer agreed that the employee’s 1979 work injury was a substantial contributing cause of the employee’s need for the surgery.

The employee’s low back surgery was considered extremely successful, initially, and the employee reported nearly complete relief from his symptoms.  As time went on, however, especially after discontinuance of narcotic medication, the employee’s low back and leg pain recurred.

In August of 2004, the employee was seen by Eric Salman, a physician’s assistant working with Dr. Buttermann.  The office record from that consultation reads in part as follows:

The employee underwent surgery to remove the fusion hardware in December of 2004.  The fusion remained solid, but the employee developed right thigh pain.  In an office note from a February 21, 2005, follow up examination, Dr. Buttermann diagnosed the right thigh pain as meralgia paresthetica^[1] and prescribed a Medrol Dosepak.  The doctor also gave the employee another prescription for Cialis, with three refills, but he advised the employee that “he should get this from his primary care physician or urologist in the future.”

The employee claimed entitlement to payment of the cost of Cialis, and the matter came on for hearing before a compensation judge on August 3, 2005.^[2]  At hearing, the employee testified that he had never had any problem with erectile dysfunction prior to the fusion surgery, that his first attempt at sexual relations after the surgery was very painful, and that the Cialis prescription has allowed him to engage in intercourse.  Other evidence submitted at hearing included some of Dr. Buttermann’s records as well as reports from Dr. Paul Cederberg, the employer’s independent examiner.

In a decision issued on September 19, 2005, the compensation judge concluded that the employee’s erectile dysfunction was causally related to the employee’s work injury and that the prescribed Cialis was reasonable and necessary to treat that condition.  The employer appeals.

On appeal, the Workers' Compensation Court of Appeals must determine whether "the findings of fact and order [are] clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted."  Minn. Stat. § 176.421, subd. 1 (2004).  Substantial evidence supports the findings if, in the context of the entire record, "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 evidence conflicts or more than one inference may reasonably be drawn from the evidence, the findings are to be affirmed.  Id. at 60, 37 W.C.D. at 240.  Similarly, findings of fact should not be disturbed, even though the reviewing court might disagree with them, "unless they are clearly erroneous in the sense that they are manifestly contrary to the weight of the evidence or not reasonably supported by the evidence as a whole.”  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

In support of his claim for Cialis, the employee relied largely on the September 17, 2004, office note of Dr. Buttermann, in which the doctor wrote that the employee’s “erectile dysfunction . . . is related to his back condition.”  The employee also offered his own testimony concerning the history and timing of his difficulty with sexual relations and the efficacy of Cialis in addressing those problems.  In denying the employee’s claim, the employer relied primarily on the reports of Dr. Cederberg, who wrote, in relevant part, as follows:

In his decision, the compensation judge expressly found credible the employee’s testimony that he did not have any problem with erectile dysfunction prior to his work-related fusion surgery.  The judge also expressly accepted Dr. Buttermann’s opinion, as contained in the September 17, 2004, chart note, that the employee’s erectile dysfunction was causally related to his low back condition.

On appeal, the employer contends that the compensation judge erred in accepting the causation opinion of Dr. Buttermann, in that Dr. Buttermann “did not examine the employee’s genital area”and did not explain the basis for his opinion.  The employer also points to physician’s assistant Salman’s chart note as evidence that treatment of erectile dysfunction is outside of the scope of Dr. Buttermann’s practice.  This conclusion, the employer maintains, is bolstered by the fact that Dr. Buttermann eventually advised the employee to follow up with his family physician or a urologist for treatment of that complaint.  Finally, citing the opinion of Dr. Cederberg, the employer argues that Dr. Buttermann, as an orthopedic surgeon, is simply not qualified to render either a causation opinion or treatment with respect to the employee’s alleged erectile dysfunction.  We are not persuaded.

Contrary to the employer’s argument, the fact that Dr. Buttermann did not explain the mechanism of injury or the basis for his opinion is not automatically fatal;^[3] rather, the presence or absence of such explanation is for the compensation judge to weigh.  See, e.g., Caizzo v. McDonald’s/T&K Restaurant Franchise Group, slip op. (W.C.C.A. Apr. 14, 2005).  Furthermore, the compensation judge was not required to accept the opinion of Dr. Cederberg concerning Dr. Buttermann’s alleged lack of qualification to diagnose or treat erectile dysfunction.  Dr. Buttermann may be an orthopedic surgeon, not a urologist, but he was the employee’s primary treating physician for years prior to giving the employee the Cialis prescription in September of 2004.  As a medical doctor familiar with the employee’s low back condition and an orthopedic surgeon with substantial experience with low back injuries and treatment, Dr. Buttermann clearly had adequate foundation to render an opinion tying the employee’s erectile dysfunction to his low back condition and resulting pain.  We note in this regard that the employer itself chose to refute the employee’s claim with the opinion of an orthopedist, rather than having the employee evaluated by a urologist.

An employee has the burden of proving that claimed medical expenses are reasonable, necessary, and causally related to his work injury.  Adkins v. University Health Care Ctr., 405 N.W.2d 233, 39 W.C.D. 898 (Minn. 1987).  In the present case, the compensation judge did not err in relying on the causation opinion of the employee’s treating surgeon, and that opinion is adequate to support the judge’s award of the disputed medication expenses.  We therefore affirm the judge’s decision in its entirety.