Comparison of joint mechanics of both lower limbs of THA patients with healthy participants during stair ascent and descent.

Total hip arthroplasty (THA) is a common surgical procedure for patients suffering from osteoarthritis to relieve their pain and to attempt to restore their normal locomotion patterns. Although this procedure does not restore normal mobility during activities of daily living, it remains unclear how it affects the joint mechanics of both lower limbs during stair negotiation tasks. Hence, we compared the 3D joint mechanics of both lower limbs of THA patients with matched healthy controls during stair ascent and stair descent. 3D kinematics and kinetics of both lower limbs were recorded for 20 patients having undergone unilateral THA and 20 healthy, age and body mass index matched control participants. The THA patients generated limited power at the operated hip joint, and thus compensated with larger power generation at the contralateral ankle to lift the body weight to the next step. This stair ambulation strategy, as well as others, adopted by the THA patients implied decreased activation of the lower limb musculature, which may be indicative of a muscle strength deficiency or a post-operatively adopted protective mechanism to unload the prosthesis. These asymmetric power production patterns should be addressed in rehabilitation programs pre- and post-operatively.