Motion Analysis of the Femorotibial and Patellofemoral Joints Using a 2D/3D Registration Technique

The in vivo kinematics of the knee joint has been analyzed by multiple approaches. In order to obtain the knee potion with the weight-bearing characteristic, a 2D/3D registration technique has been used. Whereas many studies have analyzed the femorotibial (FT) joint, only a few studies have reported a motion analysis for the patellofemoral (PF) joint. This paper focuses on the motions of both the FT and PF joints with the weight-bearing characteristic. An image acquisition test is conducted with weight-bearing for healthy subjects (n = 10) and patients with knee osteoarthritis (OA) (n = 10). The knee motions of the FT and PF joints are analyzed using the distribution area (DA) of a facet space map, percentage of short facet space (PS), weighted center position of the facet space map and average space distance (ASD) at 10 degree intervals of the flexion angle. In the case of knee OA patients, most ASDs of the PF joint were over 1 mm shorter than those of the healthy subjects. DAs of the PF facet space maps of the patient group were twice as large as those of the healthy group at 20 and 30 degree flexion angles. PSs of the PF joint of the patient group were over 2.5% from 10 to 40 degree flexion angles. This paper shows that the knee OA narrows the facet spaces of both FT and PF joints. In particular, the short facet space appears for the PF joint in knee OA patients.