Lower Limb Anatomy and Alignment Affect Natural Tibiofemoral Knee Kinematics: A Cadaveric Investigation.

BACKGROUND: During flexion, normal knee kinematics consists of a complex combination of rolling, gliding, and rotation between femur and tibia. Although in vivo studies have shown wide interindividual variability, we hypothesized that knee kinematics is either correlated to the anatomy of the individual knee joint or to the anatomic alignment of the entire lower extremity.

METHODS: The passive kinematics of 10 healthy knees was assessed in whole cadavers using a commercial computed tomography-free navigation device with intracortical pins. Rotational limb alignment or local anatomic parameters obtained by computed tomography scan or within a navigational procedure were correlated to tibial internal rotation and tibiofemoral abduction during flexion.

RESULTS: Mean tibial adduction in full extension was 3.3° (range -2.2° to 7.8°). Tibial abduction and internal rotation showed significant interindividual variability, measuring 3.9° (range -0.8° to 9.7°) and 4.9° (range -3.5° to 14.8°) during flexion. An increase in both the mechanical tibiofemoral axis and the mechanical lateral distal femoral angle correlated with increased tibial internal rotation, whereas a decrease in the mechanical medial proximal tibial angle and an increase in the mechanical tibiofemoral axis were associated with increased tibial adduction.

CONCLUSION: The main finding of the present study is that knee kinematics is influenced by both intra-articular and extra-articular parameters. These results may be of interest in component alignment in total knee arthroplasty, correction of deformities, and malalignment after fracture healing of the lower extremity. Possible relationships should be investigated in future studies.