3D in vivo femoro-tibial kinematics of tri-condylar total knee arthroplasty during kneeling activities.

Abstract

Kneeling position can serve as an important posture, providing stability and balance from a standing position to sitting on the floor or vice-versa. The purpose of the current study was to determine the kinematics during kneeling activities after subjects were implanted with a tri-condylar total knee arthroplasty. Kinematics was evaluated in 54 knees using fluoroscopy and a three-dimensional model fitting approach. The average knee flexion at before contact status, at complete contact and at maximum flexion was 98.1±9.0°, 107.2±6.7°, and 139.6±12.3°, respectively. On average, there was no gross anterior displacement from before contact status to complete contact. Only slight posterior rollback motion of both condyles from complete contact to maximum flexion was observed. Three of 39 (7.7%) knees experienced anterior movement of both condyles more than 2mm from before contact status to complete contact. Reverse rotation pattern from before contact status to complete contact and then normal rotation pattern from complete contact to maximum flexion were observed. Condylar lift-off greater than 1.0 mm was observed in 45 knees (83.3%). The presence of the ball-and-socket joint articulation provides sufficient antero-posterior stability in these designs to enable the patients to kneel safely without the incidence of any dislocation. This study suggests a safe implant design for kneeling.