By order of the court these two appeals were consolidated for argument and submitted on the same record, and were argued before the court at the same time.
No. 13589
Issues presented by the appeal of claimant attacking the Industrial Commission’s order granting claimant an award of permanent partial disability in the amount of 10% loss of the leg at the hip will be discussed first.
On January 9, 1978, Mr. Harold Houser was an employee of Southern Idaho Pipe and Steel, Inc., earning $170.00 per week as a diesel mechanic. While working that day on a truck, Mr. Houser fell from the cab of the truck, injuring his left knee. Mr. Houser was subsequently seen by his family physician, Dr. Randall J. Slickers, of Twin Falls. When Mr. Houser’s condition failed to improve as the result of Dr. Slicker’s treatment, the doctor referred Mr. Houser to Dr. Michael Phillips, an orthopedic surgeon. Dr. Phillips subsequently performed a meniscectomy (surgical removal of torn cartilage from the knee joint). Since that time, Mr. Houser has been under the continuing care of Dr. Slickers.
Notice of the accident was given within sixty days to the employer. The employer had secured its liability under the Workmen’s Compensation Act through United States Fidelity and Casualty Company. A dispute arose between Mr. Houser, his employer, and its surety concerning the extent of liability for Mr. Houser’s injury. The parties being unable to reach an agreement, Mr. Houser filed an application for hearing with the Industrial Commission. A hearing was set for and subsequently held on August 7, 1979. The Commission determined that the issues before it were the period of Mr. Houser’s total temporary disability and the nature and extent of Mr. Houser’s permanent disability.
Dr. Slickers testified that traumatic arthritis is present in Mr. Houser’s left knee, that Mr. Houser had undergone a prolonged recovery period, and, in his opinion, Mr. Houser will not be able to return to work in his usual occupation. Dr. Slickers made no statements as to whether further surgery is required.
Mr. Houser testified that his left knee has not quit hurting since the meniscectomy was performed. He observed that the knee joint has been degenerating rather than improving. Mr. Houser further testified that he is unable to stand any long length of time and that on occasion his knee “will go out from under him.” In addition to his knee injury, Mr. Houser testified that he injured his back in falls in June and August *443of 1978, which he believed had been caused by the buckling under of his knee. He stated that he had constant pain in his lower back area and could not sit for any prolonged period of time because of the pain. Mr. Houser also testified that he could not do sedentary work because his back injury prevented him from sitting long enough to do that type of work.
Mrs. Houser’s testimony was corroborative of her husband’s testimony.
At the hearing, medical reports of Dr. Phillips were entered into evidence. The reports indicated that Dr. Phillips could find nothing during his post-operative examination of Mr. Houser to justify additional surgical procedure or medical treatment. He discontinued Mr. Houser’s physical therapy in October 1978. Dr. Phillips examined Mr. Houser again on January 29, 1979, at which time he deemed it appropriate to give Mr. Houser a permanent physical impairment rating. His report of the examination stated that Mr. Houser was going to work and rated Mr. Houser with a 10% permanent physical impairment of the lower extremity.
The Commission also allowed the hearing to be continued to obtain the testimony of Dr. Keith Taylor, an orthopedic surgeon, by deposition. Dr. Taylor had examined Mr. Houser at the request of the employer and its surety and subsequently ordered arthoscopy of the knee.1 The arthoscopy was performed at St. Alphonsus Hospital in Boise in January 1979. As a result of the examination and arthoscopy, Dr. Taylor was unable to substantiate Mr. Houser’s complaints of instability and pain in the knee, and that Mr. Houser should be able to return to employment. Dr. Taylor also rated Mr. Houser’s permanent physical impairment at 10% compared to the loss of the leg at the hip.
With this testimony before it, as well as the medical reports and other evidence available to it, the Industrial Commission entered its findings of fact and conclusions of law on December 19,1979. The Commission found that Mr. Houser’s condition was stable as of January 15, 1979, and that the employer and its surety had paid sums totaling $4,936.83 in disability benefits. The Commission further found that Mr. Houser only suffers a permanent partial disability of 10% of the loss of the leg at the hip as a result of the January 9, 1978, industrial accident. It also found that the record does not establish that further surgery on Mr. Houser’s knee is reasonably required as a result of the accident, but that Mr. Houser will require elastic knee braces.
The Industrial Commission concluded as a matter of law that Mr. Houser had failed to establish by a preponderance of the evidence that he suffers a permanent disability in excess of 10% loss of the leg at the hip or that further surgery is necessary. It therefore ordered that Mr. Houser is entitled to total temporary disability benefits from the period commencing January 9, 1978, and ending January 15,1979, that the employer and surety receive a credit in the amount of $4,936.83 against the sum due, that Mr. Houser receive an award of permanent partial disability in the amount of 10% of loss of the leg at the hip, and that the employer and surety pay the cost of all reasonable and necessary medical expenses for a reasonable period of time, including elastic knee braces, but that future surgical procedures have not been established as reasonably necessary.
In workmen’s compensation cases, the court’s review is limited to questions of law and determinations of whether the findings of fact of the Industrial Commission are supported by substantial, competent evidence. I.C. §§ 72-724(2) and 72-732(1); Sykes v. C. P. Clare & Co., 100 Idaho 761, 605 P.2d 939 (1980); Paulson v. Idaho Forest Industries, Inc., 99 Idaho 896, 591 P.2d 143 (1979); Madron v. Green Giant Co., 94 Idaho 747, 497 P.2d 1048 (1972). If the findings of fact of the Industrial Commission are supported by substantial, compe*444tent evidence, they will not be disturbed on appeal. Dean v. Dravo Corp., 97 Idaho 158, 540 P.2d 1337 (1975); Gradwohl v. J. R. Simplot Co., 96 Idaho 655, 531 P.2d 775 (1975). Claimant challenges the sufficiency of the evidence in this regard as to the Commission’s findings of fact that he suffers only a permanent partial disability of 10% loss of the leg at the hip.
In the instant case, the Commission had before it the expert medical testimony of Dr. Taylor. Concerning Dr. Taylor’s qualifications, he testified that as an orthopedic surgeon he had for a period of some eighteen years, on numerous occasions, evaluated patients for purposes of permanent impairment ratings as they pertain to industrial accident cases in this state. Dr. Taylor stated that, based on his examination of claimant and the results from the arthoscopy, claimant had a permanent physical impairment equivalent to 10% as compared to the loss of the leg at the hip. On the issue of whether claimant had reached a stable condition so that additional medical treatment would not be required, Dr. Taylor testified that in his opinion claimant’s condition was stable. Regarding claimant’s complaints of disabling pain, Dr. Taylor rendered the following opinion.
“A. Again, these are subjective complaints and you have to base your opinions and findings on subsequent subjective findings on examination and that’s— to aid your conclusions. And these are not objective findings, they are subjective complaints.
Q. Well, do you take the stand, then, if you have a subjective complaint and a person says that I am suffering pain, that you do not give this subjective finding validity?
A. Not if they are — if there’s a lack of any significant subjective findings to back it up.”
Q. And, Doctor, that being the case, do you know of any medical reason why the leg would give out, the knee would give out each day due to instability; can you explain that medically?
A. You mean in this individual?
Q. Yes.
A. No.
Q. And, Doctor, insofar as your examination and subsequent hospitalization and procedure is concerned, from a medical viewpoint, can you substantiate this man’s complaints of pain as related to you by Mr. McCarthy?
A. No.”
Finally, on the issue of whether claimant could engage in gainful employment and/or return to his former vocation. Dr. Taylor stated his opinion as follows:
“Q. Doctor, as I understand it, the claimant at the time of this accident, and he does have experience as a heavy equipment mechanic, a diesel mechanic, doing mechanical work on vehicles and heavy equipment; this is basically what the man has done for a large portion, at least, of his lifetime, doing maintenance work and diesel mechanic work, he had done this for a period of some thirteen years. Doctor, are you aware of, generally, what is required of a heavy equipment and diesel mechanic?
A. Yes.
Q. You have observed and seen, from time to time, heavy construction equipment, large trucks, this sort of thing? A. Yes.
Q. From a medical standpoint, is there any reason that you know of why the claimant could not engage in that type of gainful employment?
A. No.”
Admittedly, the testimony of Dr. Slickers, as summarized earlier, is at variance with the professional opinions of Dr. Taylor. Nonetheless, the testimony of Dr. Taylor as detailed above constitutes substantial competent evidence supporting the Commission’s findings of fact that claimant suffers a permanent partial disability of 10% loss of the leg at the hip. Sykes v. C. P. Clare & Co., supra; Thom v. Callahan, 97 Idaho 151, 540 P.2d 1330 (1975).
The claimant next asserts that the Commission failed to fulfill its duty to consider *445both medical and nonmedical factors in its evaluation of claimant’s permanent disability. As to this assertion, claimant directs the court’s attention to I.C. § 72-422, which states in part, “[permanent impairment is a basic consideration in the evaluation of permanent disability, and is a contributing factor to, but not necessarily an indication of, the entire extent of permanent disability.” See I.C. § 72-425. Consistent with I.C. §§ 72-422 and 72-425, claimant also directs the court’s attention to the statement in Lyons v. Industrial Special Indemnity Fund, 98 Idaho 403, 406, 565 P.2d 1360, 1363 (1977), that “[i]n addition to the medical factors of permanent impairment, the Commission must also consider nonmedical factors such as age, sex, economic and social environment, training and usable skills.” See also, Murray v. Hecla Min. Co., 98 Idaho 688, 571 P.2d 334 (1977); Francis v. Amalgamated Sugar Co., 98 Idaho 407, 565 P.2d 1364 (1977).
The position advanced by claimant appears to be that whenever a permanent physical impairment rating is given, the disability rating in all cases must exceed the permanent physical impairment rating by taking into consideration the various nonmedical factors outlined under the workmen’s compensation law. The problem facing claimant is that there is no such evidence in the record bearing on any disability above and beyond the physical impairment rating.
Finally, claimant asserts that the Commission erred in its conclusion of law that claimant had failed to establish by a preponderance of the evidence that he suffers a permanent disability in excess of 10% loss of the leg at the hip. In this light, claimant’s argument appears to boil down to the fact that a greater number of witnesses supported a view different from the conclusion reached by the Commission. The fact that a greater number of witnesses supported a view different from the conclusion reached is of no moment in determining the preponderance of the evidence. Arnold v. Splendid Bakery, 88 Idaho 455, 401 P.2d 271 (1965). Rather, the determination must be based on an assessment of the reliability, trustworthiness, and probative value of the evidence. As such, the determination is in the first instance a question of fact committed to the particular expertise of the Commission; and its determination as to the weight and credibility of the testimony is conclusive on appeal unless it appears to be clearly erroneous. Arnold v. Splendid Bakery, supra. Claimant has failed to make such a showing, and therefore, it cannot be said that the Commission erred in its conclusion that claimant had failed to meet his burden of proof.
No. 14207
Issues raised by the appeal of claimant challenging the Industrial Commission’s order denying his subsequent application for a hearing will next be discussed.
During the pendency of the appeal in no. 13589, in late November 1980, claimant filed an application for a hearing with the Industrial Commission, alleging an injury to his back in August of 1978 was the direct result of the knee injury he sustained in January of 1978 while in the employ of Southern Idaho Pipe and Steel, Inc. The employer and its surety duly filed an answer to the application. The answer included a motion to dismiss on the ground that the compensability of claimant’s back injury had already been decided by the Commission in the prior hearing.
Oral argument on the motion to dismiss was heard February 25,1981, before referee Robert C. Youngstrom. The referee thereafter submitted to the Commission his report and recommendation that an order be entered dismissing the application for hearing, reasoning that:
“The difficulty which the claimant encounters in his present case is that he has previously litigated this issue. An examination of the transcript of proceedings, which is now on appeal to the Supreme Court, shows that the claimant testified, at length, about his back injury and his back condition which he contended was caused by a fall due to his unstable left knee. The Commission heard this evi*446dence and then entered a decision awarding the claimant certain workmen’s compensation benefits for the consequences of his injury. This is the matter which is now on appeal ....
Under the doctrine of res judicata a judgment on the merits, in a prior action, bars a second action involving the same parties based on the same cause of action. Where a second action is brought upon a different cause of action, the doctrine of collateral estoppel precludes relitigation of issues actually litigated and necessary to the outcome of the first action. The Referee concludes that, because the claimant litigated his alleged back injury in the prior action, which is now on appeal to the Supreme Court, he is precluded from relitigating the matter in the present action before the Commission.”
Upon review of the referee’s report and recommendation, on April 27, 1981, the Industrial Commission ordered that the application for hearing be dismissed. We affirm.
Under the doctrine of res judicata, a judgment on the merits in a prior proceeding bars a subsequent lawsuit between the same parties upon the same cause of action. Ramseyer v. Ramseyer, 98 Idaho 554, 569 P.2d 358 (1977); Joyce v. Murphy Land & Irrig. Co., 35 Idaho 549, 208 P. 241 (1922). The “sameness” of a cause of action for purposes of application of the doctrine of res judicata is determined by examining the operative facts underlying the two lawsuits. Restatement (Second) of Judgments, § 61, Comment a (Tent.Draft no. 1 1973).
In the prior proceeding, the claimant sought workmen’s compensation benefits for total and permanent disability on the basis of the knee injury sustained in the industrial accident on January 9, 1978 and back injuries allegedly sustained in falls in June and August 1978, which were said to have been occasioned by the instability of his injured knee. Claimant testified at length about these alleged back injuries and their effects on his physical condition and his ability to be employed. In claimant’s subsequent application for hearing in the instant case, he sought additional compensation for back injuries allegedly sustained in a fall in August 1978, which was allegedly occasioned by the instability of claimant’s previously injured knee. This is the same incident which formed the basis for claimant’s claim of total and permanent disability in the prior proceeding. In sum, the proceeding in the instant case and in the prior proceeding arose out of the same operative facts between the same parties. The Commission properly dismissed the application for hearing on the basis of the doctrine of res judicata. Given this conclusion, the applicability of the doctrine of collateral estoppel need not be discussed.
The order of the Industrial Commission granting claimant an award of permanent partial disability is affirmed. The order of the Industrial Commission dismissing claimant’s subsequent application for a hearing is affirmed. Costs to respondents.
BAKES, C. J., and DONALDSON and SHEPARD, JJ., concur.. Arthoscopy is an examination of the interior of a joint by use of an instrument known as an andoscope.