delivered the opinion of the court:
Claimant, Edward Gibson, appeals from an order of the circuit court of Cook County confirming a decision of the Industrial Commission (Commission) denying him benefits from the respondent, General Motors Corporation.
At the hearing before the arbitrator, the following evidence was introduced. Claimant had been employed by the respondent since 1965, as a painter. On September 20, 1982, while walking down a scaffold behind a foreman, he hit the biceps of his left arm on a steel subbase door which was sticking out. He felt pain but did not notice it much at the time because he was busy checking a car. He did not report the accident at that time. A few days after it happened, he noticed it turning black and blue.
On September 21, 1982, claimant contracted the flu. He was treated by his family physician, Dr. Steven Jacula, and was off of work until October 6, 1982. After working a few days, his arm bothered him, and he could not lift anything. He went to see Dr. Mitchell, the company doctor, who told him not to worry about it, that it would go away in a few months. After about a week, he had a reoccurrence of the flu. He saw Dr. Jacula on October 1, 1982, when for the first time he mentioned the problem with his arm to Dr. Jacula. Dr. Jacula’s records for that date show that claimant was given a flu shot, advised to report the medical services at work, and use a heating pad as necessary.
On October 19, 1982, claimant reported the alleged injury to the company medical department. Dr. Mitchell’s report noted “a pecan-size mass on the mid-biceps muscle” and diagnosed a “resolving hematoma.”
On November 19, 1982, claimant saw Dr. Edward A. Wojcik, who had previously treated a knee problem for him. After a physical exam *402and X rays were taken, Dr. Wojcik’s impression was that claimant's condition was “[p]robably a chronic tendinitis [sic] of the left shoulder with a rupture of the long head of the biceps tendon and subsequent distal migration of the biceps belly.” He informed claimant that while no treatment was necessary for this condition, sometimes surgery was performed to bring up the muscle belly but that there was no guarantee that this would give his arm any strength. Claimant was not interested in having the surgery at that time.
On April 4, 1983, claimant went to Dr. Wojcik again, complaining of pain in the region of the muscle belly of the left biceps when he tried to lift anything heavy. The physical examination revealed “claimant has a positive impingement sign. He did seem to lack the last 10° or so of full abduction of the left arm. The muscle belly of the left biceps had moved distally because of the apparent rupture of the long head of the biceps.” Again, Dr. Wojcik could not guarantee that surgery would correct the position of the muscle belly. In his April 9, 1983, report, Dr. Wojcik noted that claimant’s wife, who had accompanied claimant to the examination, stated that claimant had complained of pain in his shoulder before, and claimant stated that it was arthritis. Dr. Wojcik also noted that claimant’s condition “could have been aggravated by the apparent contusion which the patient sustained at work.” In a May 5, 1983, telephone conversation with claimant’s wife, Dr. Wojcik told her that very often the tendon can rupture without any injury when there is chronic bursitis about the shoulder.
Between October 1982 and June 1983, claimant’s arm continued to bother him a great deal, and he finally could not lift anything. In June 1983, Dr. Jacula referred claimant to Dr. Boone Brackett. Claimant was admitted to West Suburban Hospital from June 14, 1983, through June 17, 1983, for surgery by Dr. Brackett to reattach the biceps muscle to the periosteum. After his release from the hospital, claimant continued to see Dr. Brackett for follow-up visits. He was released to return to work on August 15, 1983. On August 25, 1983, his last visit to Dr. Brackett, the doctor commented in his notes, “His motion is fantastic, he has good power and I think this thing is excellent! He is doing absolutely well.”
On October 15, 1983, at his attorney’s request, claimant was examined by Dr. Barry Fischer. According to Dr. Fischer’s report, claimant complained of weakness in his left arm. He diagnosed claimant as suffering from a “strain injury to the upper left arm with rupture to the left biceps muscles.” He noted “a decreased range of motion of the left upper arm at the shoulder with asymmetry of the left upper arm,” and “residual atrophy of the left arm with a decreased *403motor strength.”
On December 16, 1983, at the request of the employer, claimant was examined by Dr. E. Thomas Marquardt. In the doctor’s opinion, claimant had a full range of motion of the left shoulder and elbow. He noted the operation scar and observed that “when claimant was flexing the left elbow and tightening the biceps musculature, it could be seen that the biceps muscle belly itself is not normal in contour,” and “is retracted somewhat distally.” Strength of the biceps muscle to manual testing was excellent. Dr. Marquardt also pointed out that “the great majority of long head of the biceps tendon ruptures occur spontaneously.” Dr. Marquardt felt claimant could work without restriction.
The arbitrator found that claimant’s unrebutted testimony established that the accident occurred and that the foreman who was alleged to be present was not produced to rebut the accident. The period of disability had been stipulated to by the parties. Claimant was awarded $220 for medical expenses and $282.25 per week for 105½ weeks for permanent and complete loss of 45% of the use of the left arm.
On review, the Commission reversed the decision of the arbitrator, basing its decision on the fact that claimant failed to report the alleged accident or seek medical care after it happened and the opinions of Drs. Wojcik and Marquardt that the tear could have developed spontaneously with that type of trauma.
The claimant appealed the decision of the Commission to the circuit court of Cook County. The circuit court determined that the decision of the Commission was not against the manifest weight of the evidence and confirmed the decision of the Commission. This appeal followed.
The single issue raised on appeal is whether the decision of the Commission is against the manifest weight of the evidence.
It is primarily within the province of the Commission to determine a question of fact; nevertheless, it is the duty of the reviewing court to weigh the evidence, and if the Commission’s decision is against the manifest weight of the evidence, it must be set aside. (Allis-Chalmers Manufacturing Co. v. Industrial Comm’n (1966), 35 Ill. 2d 367.) A court will not overturn the Commission’s findings simply because a different inference could be drawn or otherwise substitute its judgment for that of the Commission. (Niles Police Department v. Industrial Comm’n (1981), 83 Ill. 2d 528, 533-34.) Further, where the evidence is conflicting or of such a nature that different inferences may be drawn therefrom, a reviewing court will not disregard a per*404missible inference drawn by the Commission merely because other inferences may be drawn. (Sterling Steel Casting Co. v. Industrial Comm’n (1979), 74 Ill. 2d 273, 277.) It is for the Commission to decide which of two conflicting medical opinions given in a case is the accepted. Caterpillar Tractor Co. v. Industrial Comm’n (1983), 97 Ill. 2d 35, 43.
Claimant cites International Harvester Co. v. Industrial Comm’n (1973), 56 Ill. 2d 84, for the proposition that an injury is accidental within the meaning of the Workers’ Compensation Act when it is traceable to a definite time, place, and cause and occurs in the course of employment unexpectedly and without affirmative act or design of the employee. Claimant then argues that he has satisfied the test in that on September 20, 1982, he hit the biceps of his left arm on a steel subbase door and that this occurred unexpectedly and during the course of his employment. However, the Commission found based upon the record before it that claimant failed to prove that he had, in fact, struck his left arm as he described on September 20, 1982.
Claimant’s reliance on Board of Education v. Industrial Comm’n (1983), 96 Ill. 2d 239, and Nickey Chevrolet Sales, Inc. v. Industrial Comm’n (1967), 37 Ill. 2d 399, is equally misplaced. In Board of Education, the issue was the existence of a causal connection between decedent’s undisputed fall from a ladder and the development of his fatal brain tumor. In the present case, the existence of the accidental injury itself is disputed. We note, however, that in the above case, the Commission’s resolution of the conflicts in the medical testimony was upheld. In Nickey Chevrolet Sales, claimant’s husband, a salesman for the respondent, had been struck and killed by an automobile as he left work. The arbitrator denied benefits, but the Commission reversed and awarded benefits. The award was confirmed by the circuit court. On review, our supreme court affirmed the Commission’s finding that the decedent’s death arose out of and in the course of his employment, noting that it is fundamental law that it is within the province of the Commission rather than the courts to draw reasonable conclusions and inferences from the evidence and facts, nor should the determination of the Commission be disturbed unless its conclusion cannot legitimately be inferred from the evidence below it.
Based upon our review of the record in this case, we are satisfied that the Commission’s findings were based upon facts and permissible inference from the record, and on that basis, this court may not overturn those findings or otherwise substitute our own opinion for that of the Commission. Niles Police Department v. Industrial Comm’n (1981), 83 Ill. 2d 528.
*405Therefore, we conclude that the decision of the Commission is not against the manifest weight of the evidence.
Affirmed.
McNAMARA and McCULLOUGH, JJ., concur.