Diagnosis of the disorders following menlscectomy is occasionally difficult, as ther has frequently been involved many causes other than the torn menisci. The retained fragments of the menisci have been blamed to be responsible for postoperative knee disorders. Arthroscopic examination was carried out in 40 knees after meniscectomy and the frequency of retained posterior horn in relation to the postoperative trouble was observed. 1. In 11 out of total 40 knees, the retained posterior horn could be diagnosed, consisting of 27.5% of all. 2. Only flve of these 11 knees showed some kinds of postoperative disorders,while the reat had no trouble. 3. Those knees in which the excision of the posterior horn was incomplete, were often associated with Irregular healing pattern of the local tissue, which might be closely related to the occurrence of the secondary Intraarticular change.