RISING FROM CHAIR AFTER TOTAL KNEE ARTHROPLASTY

Objective. This study was performed to determine the biomechanics of c hair rising by patients after successful total knee arthroplasty (TKA) . Design. Relative full body joint positions and ground reaction force s were measured by a motion analysis system and two force plates. Back ground. Chair-rise produces increased joint forces and moments compare d with level walking, and it is difficult to rise from a chair for mos t patients with neurological or musculoskeletal abnormalities. Previou s motion studies of patients after TKA had focused on gait analysis an d stair climbing. Methods. Twelve patients after successful TKA were s tudied while performing sit-to-stand transfer from a chair at four cha ir heights without the use of arm rests. The results of this group wer e compared with those of 12 healthy elderly subjects and 14 osteoarthr itic patients before TKA. Results. Compared with the healthy elderly g roup during chair rising, the patients after TKA had increased horizon tal mass center velocity, increased vertical hip joint forces, the max imum sound-side hip extension moment, but decreased vertical mass cent er velocity. Conclusion. Compensatory mechanisms of chair rising were adopted by the arthritic patients before and after TKA. The mechanisms include increased forward body bending and more weight shift on the s ound side. Relevance Osteoarthritic patients after successful TKA had nearly normal biomechanics in rising from a higher chair. Therefore, t hey are better advised to use chairs of at least the same height as th eir lower leg segment. (C) 1998 Elsevier Science Ltd. All rights reser ved.