Degenerative arthritis was found in 18 knees examined in 70 cases of internal derangement of the knee joint seen during the past 3 years. Eleven of these patients, who did not respond to conservative treatment, underwent arthrotomy with medial meniscectomy, and in each of these cases attritional degeneration of the medial meniscus, secondary to degenerative arthritis, was found to have led to rupture of the meniscus. Full flexion or extension of the involved knee, due to displacement of the torn meniscus, was impossible in each case. Excision of the torn cartilage permitted return of function to these arthritic knee joints. TRAUMATIC DERANGEMENT of the semilunar cartilages of the knee joint is a common entity, familiar to every orthopedic surgeon. How¬ ever, rupture of menisci can occur on an attritional basis alone, secondary to osteoarthritis, and with¬ out precipitating trauma. As such patients are all elderly and as these joints bear the other stigmata of degenerative disease, symptoms are often at¬ tributed to the arthritis per se and the offending meniscus lesion may be overlooked. It has been our experience that arthrotomy and excision of the involved meniscus offers relief not afforded by the usual conservative treatment of the arthritic knee. It is the purpose of this report to describe the diagnosis and management of such cases and to present 11 examples of this pathology that have been confirmed by operation.In 1954, Smith and Blair described degenerative changes of the menisci that led to deformity and sometimes to displacement.1 The presenting clini¬ cal picture in their series, 30 of which were con¬ firmed by operation, was that of tibial collateral ligament strain. There was no history of locking in any of the kness they described.Lagergren,2 in reviewing 97 cases of meniscec-tomy, discussed the development of degenerative arthritis in the joints that were operated on. In the diseussion of this paper Waldenström pointed out that "chronic, irritative conditions in a joint may give rise to arthritis deformans." It is interesting to speculate on the possibility of an attritional menis¬ cus lesion simulating such a condition and acceler¬ ating the degenerative process in the involved joint. Magnuson,3 Isserlin,4 and others have described operative removal of degenerated menisci as part of a surgical program for the treatment of ad¬ vanced degenerative arthritis of the knee. Pathology Attritional degeneration of the semilunar carti¬ lages occurs during the course of osteoarthritic degeneration of the knee joint. This soft tissue degeneration is secondary to the articular incon¬ gruity and abnormal joint excursion which occurs in this disease. Minor strains to the knee, such as those incurred in squatting, twisting, entering an automobile, and the like, can accelerate this proc¬ ess and lead to fibrillation and marginal fraying of either meniscus. If a focal area of semilunar carti¬ lage undergoes severe attritional degeneration, tear¬ ing of the cartilage can occur and cause displace¬ ment of a loose ta...