Tibiofemoral kinematic analysis of kneeling after total knee arthroplasty.

Some surgeons warn against kneeling after total knee arthroplasty (TKA), because limited clinical data exist. We describe the tibiofemoral contact position of TKA components during kneeling in vivo. Ten posterior-substituting (PS) and 10 cruciate-retaining (CR) designs were examined using a radiographic image-matching technique. Movement from standing to kneeling at 90 degrees produced different responses. CR knees translated anteriorly (medial, 4 +/- 4 mm; lateral, 2 +/- 6 mm). PS knees underwent little posterior translation (medial, 0.2 +/- 3 mm; lateral, 1 +/- 4 mm). Movement from 90 degrees to maximum flexion produced femoral posterior translation (CR medial, 5 +/- 4 mm; CR lateral, 5 +/- 4 mm; PS medial, 6 +/- 4 mm; PS lateral, 6 +/- 3 mm). The relationship between tibiofemoral contact position and flexion angle was more variable for CR (r2=.38) than for PS (r2=.64). Knee kinematics was similar to other deep-flexion weight-bearing activities.