The natural course of primary osteoarthritis of the knee with or without treatment by intraarticular corticosteroid injections was investigated in 446 patients presenting from 1970 to 1973. Sixty-one of these patients were able to be followed up in 1982 and were divided into two groups. One group included 53 patients (82 knees) without corticosteroid injections. The other group had eight patients (14 knees) who received intraarticular steroids (mean number of injections: 25; range:4-78). The standing femorotibial angle at followup in the male patients receiving injections (p < 0.05) was four degrees of greater varus angulation. Radiographic degeneration was more advanced in 11 of the 24 steroid-treated knees (78.6%), and in 43 of the 82 knees without steroid injections (52.4%) (p < 0.01).