Degenerative arthritis of the knee joint is one of the main causes of disability in middle-aged persons. This paper is planned by the necessity of objective information upon changes of tibio-femoral angle according to weight bearing in patients with degenerative arthritis of the knee joint. The authors studied the tibio-femoral angle in 29 cases of degenerative arthritis of the knee ranging fmm 5th to 6th decades of age, and compared with 27 cases of the control group, in the Dept. of Orthopedic Surgery, S.N.U.H. fmm Mar. 1983 to May 1984. The following observations were obtained: 1. In patients with degenerative arthritis of the knee, changes of the tibio-femoral angle according to weight bearing were +2.2±1.94 in 5th decade, +2.3±2.02 in 6th decade. 2. Compared to control group, the degenerative arthritis group showed a significant varization with weight bearing. 3. It was seemed that the weight bearing radiography is essential in diagnosis and treatment of degenerative arthritis of the knee joint.