OBJECTIVE: This study was done to evaluate the frequency and to examine the difference of radiographic findings between patellofemoral joint (PFJ) and tibiofemoral joint (TFJ) in radiographic change of knee osteoarthritis (OA). METHODS: 347 Korean women (694 knees) who visited our clinic with knee joint pain took anteroposterior (AP) weight bearing view of TFJ, lateral and skyline view of PFJ of the knees from Jan. to Dec. in 1999. Radiographs were read for features of OA using Kellgren-Lawrence. The difference of frequency in two joint's radiographic changes of OA was examined using chi-square and Wilcoxon signed rank test. RESULTS: Radiographic knee OA was correlated with patient's age (r=0.482, P<0.001) and with body mass index (r=0.123, p<0.001). Frequency of radiographic OA using lateral view of PFJ was 38.8%, using AP view of TFJ was 28% and skyline view of PFJ was 23.1% (p<0.05). CONCLUSION: These results show that lateral view of PFJ with AP view of TFJ increase the frequency of radiographic knee OA, but skyline view of PFJ doesn't contribute to increase the frequency of radiographic knee OA.