Objective：This study was aimed at investigating the acquirement of socks-handling ability with hip flex, abduction, and external rotation position (hip open position）in 5 months after the posterior approach to total hip arthroplasty (THA), with consideration of the functional goals by conducting a multicenter cooperative study.Methods：The study included 101 patients (104 hip joints) with hip osteoarthritis. We evaluated patient attribution；ranges of motion of the hip, knee and ankle；hip pain in socks-handling；and upper extremity length, which were evaluated before the operation, upon hospital discharge and at 5 months after the posterior approach to THA. The patients were classified into those who attained and did not attain socks-handling ability in open hip position until 5 months after THA. We investigated the factors for acquiring socks-handling ability by using a multiple logistic regression analysis.Results：We identified three factors that significantly correlated to socks-handling ability as follows：(1) socks-handling ability before the operation, (2) range of hip external rotation before operation, and (3) range of hip abduction before discharge. The goal to acquire socks-handling ability is 27.5° hip external rotation and 17.5° hip abduction.Conclusion：We suggest that socks-handling ability must be acquired before THA and that the target range of hip abduction and external rotation must be attained during the early post-THA stage.

Objective：This study was aimed at investigating the acquirement of socks-handling ability with hip flex, abduction, and external rotation position (hip open position) in 5 months after the posterior approach to total hip arthroplasty (THA), with consideration of the functional goals by conducting a multicenter cooperative study.Methods：The study included 101 patients (104 hip joints) with hip osteoarthritis. We evaluated patient attribution；ranges of motion of the hip, knee and ankle；hip pain in socks-handling；and upper extremity length, which were evaluated before the operation, upon hospital discharge and at 5 months after the posterior approach to THA. The patients were classified into those who attained and did not attain socks-handling ability in open hip position until 5 months after THA. We investigated the factors for acquiring socks-handling ability by using a multiple logistic regression analysis.Results：We identified three factors that significantly correlated to socks-handling ability as follows：(1) socks-handling ability before the operation, (2) range of hip external rotation before operation, and (3) range of hip abduction before discharge. The goal to acquire socks-handling ability is 27.5°hip external rotation and 17.5°hip abduction.Conclusion：We suggest that socks-handling ability must be acquired before THA and that the target range of hip abduction and external rotation must be attained during the early post-THA stage.