Longitudinal joint loading in patients before and up to one year after unilateral total hip arthroplasty.

Abnormal kinematics and kinetics have been reported in hip osteoarthritis (OA) patients before and after total hip arthroplasty (THA). These changes can affect the loading of the ipsilateral hip, as well as the contralateral hip and knee joint. As it is not clear how hip and knee loading evolves in THA patients during the first year after surgery, the goal of this study is to define how joint loading changes in patients before and at three evaluation times after THA surgery. Musculoskeletal modelling in combination with gait analysis data was used to calculate hip and knee contact forces in 14 patients before and 3-, 6- and 12-months after unilateral THA, as well as in 18 healthy controls. Results showed that bilateral hip and knee loading were decreased compared to controls, both before and after THA surgery. Loading symmetry was altered compared to controls at 3-months post-surgery for the hip and at all evaluation times, except for 6-months post-surgery, for the knee, with ipsilateral joint loading decreased compared to the contralateral side. To conclude, 12-months after THA joint loading was not normalized, with both hip and knee loading in patients decreased compared to controls. Therefore, no overloading of the ipsi- or contralateral hip and knee joint was found before and up to one year after unilateral THA.