&ITIn vivo&IT three-dimensional kinematics of normal knees during different high-flexion activities

Aims & para;& para;In Asia and the Middle-East, people often flex their knees deeply in order to perform activities of daily living. The purpose of this study was to investigate the 3D kinematics of normal knees during high-flexion activities. Our hypothesis was that the femorotibial rotation, varus-valgus angle, translations, and kinematic pathway of normal knees during high-flexion activities, varied according to activity.& para;& para;Materials and Methods & para;& para;We investigated the in vivo kinematics of eight normal knees in four male volunteers (mean age 41.8 years; 37 to 53) using 2D and 3D registration technique, and modelled the knees with a computer aided design program. Each subject squatted, kneeled, and sat cross-legged. We evaluated the femoral rotation and varus-valgus angle relative to the tibia and anteroposterior translation of the medial and lateral side, using the transepicodylar axis as our femoral reference relative to the perpendicular projection on to the tibial plateau. This method evaluates the femur medially from what has elsewhere been described as the extension facet centre, and differs from the method classically applied.& para;& para;Results & para;& para;During squatting and kneeling, the knees displayed femoral external rotation. When sifting cross-legged, femurs displayed internal rotation from 10 degrees to 100 degrees. From 100 degrees, femoral external rotation was observed. No significant difference in varus-valgus angle was seen between squatting and kneeling, whereas a varus position was observed from 140 degrees when sifting cross-legged. The measure kinematic pathway using our methodology found during squatting a medial pivoting pattern from 0 degrees to 40 degrees and bicondylar rollback from 40 degrees to 150 degrees. During kneeling, a medial pivot pattern was evident. When sifting cross-legged, a lateral pivot pattern was seen from 0 degrees to 100 degrees, and a medial pivot pattern beyond 100 degrees.& para;& para;Conclusion & para;& para;The kinematics of normal knees during high flexion are variable according to activity. Nevertheless, our study was limited to a small number of male patients using a different technique to report the kinematics than previous publications. Accordingly, caution should be observed in generalizing our findings.