The purpose of this study was to observe the change of circumference, volume and strength of normal 'and operated lower extremities on 3rd, 7th, 10th, and 14th days of postoperation following THRA compared with their condition on preoperation day. Subjects consisted of 13 male and 7 female patients operated with THRA between the age of 20 and 69 years with a mean age of 38.55(SD=15.1). Circumference of upper and lower leg was measured by tape, leg volume was determined according to formula (Moor and Thornton, 1987) with measurement of 8 circumferences of leg. Leg strength was measured by pressing the center of digital health meter in supine position. The results can be summarized as follows: 1. Circumference of operated thigh decreased significantly at 14 following THRA compared with preoperative value, while that of normal thigh decreased significantly at day 3, 7, 10 and 14 after THRA compared with preoperative value. 2. Circumference of midcalf in both operated and normal limb decreased significantly at day 3, 7, 10 and 14 following THRA compared with preoperative value. 3. Leg volume of operated lower limb decreased significantly at 10, 14 following THRA compared with preoperative value, while that of normal limb decreased significantly at day 7 and 10 after THRA compared with preoperative value. 4. Leg strength of operated limb decreased significantly at day 3, 7, 10, 14 following THRA compared with preoperative value. No significant difference of normal leg strength was shown following THRA. 5. Circumference of midcalf differed significantly at day 14 after THRA between normal and operated extremity. From these results, it can be suggested that a decreased activity after THRA caused muscle atrophies in normal and operated extremity.