The flexion contracture of knee was developed in long-standing knee joint arthritis like degenerative osteoarthritis and rheumatoid arthritis. One of the objectives in total knee replacement arthro-plasty (TKA) is to correct flexion deformity which is the frequent consequence of rheumatoid arthritis (RA) and osteoarthritis (OA). We defined the severe flexion contracture as above 30degrees deformity of knee joint. A review of 337 primary TKA was carried out between August 1989 and March 1995. We found that such deformity was present in 106 Knees (31.5%) of knees before the operation. We analysed the changing pattern and amount of improvement in flexion contracture with 70 knees, which we can follow up over 1 year (average 28.9 months). We corrected flexion contracture deformity only 62.7% in RA (29.2degrees out of 46.5degrees) and 85% in OA (30.4degrees out of 36.8degrees ). So the remaining flexion contracture immediate after TKA is 17.3degrees in RA and 6.4degrees in OA. After the operation, we educate the patient and care person to perform the knee joint stretching by intermittent gentle passive extension exercise for residual flexion contracture. In RA, the remaining flexion contracture immediate after TKA would be improved in follow-up period. At 1 year after TKA, the degree of flexion contracture was not significantly different between in RA ( 7.4degrees) and OA ( 5.0degrees) (independent t-test, P>0.05). The angle of further flexion of knee joint was not increased after TKA compare to preoperative angle, but the range of motion of knee joint was increased, so the increased range of motion was influenced only by the corrected flexion contracture degree. The American Knee Society Knee and Function scores were improved after the TKA (P<0.05). So we recommand that in RA, there is no need to correct the severe flexion contracture completely and it is permissible to remained residual flexion contracture within 1/3 of initial deformity, but in OA, correct the flexion contracture deformity completely during TKA procedure as possible.