We performed intra-osseous venography in 16 patients with chondromalacia patellae or patellofemoral osteoarthritis. Of 16 patients, eight patients had chondromalacia patellae and 6 patellofemoral osteoarthritis. Two patients with normal patellae who underwent meniscectomy were used as controls. The results obtained were as follows: 1. Dye congested in the normal patella was disappeared within 2 minutes after injection and extra-osseous drainage pattern disappeared within 1 minute. 2. in chondromaiacia patellae, large amount of dye was spread throughout the entire patella and remained till 10 minutes, while extra-osseous drainage pattern disappeared at about 5 minutes. 3. In patellefemoral osteoarthritis, venous engorgment in patella was similar to that of chondromalacia patellae and extra-osseous drainage pattern disappeared at about 10 minutes. Conclusively, authors thought the patella I.O.V. was one of the significant clinical methods to define the etiological factors of the various patellofemoral disorders such as patellofemoral osteoarthritis and chondromalacia patellae.