This study tested whether the knee's center of rotation (COR) in the transverse plane sits on the medial side during walking, as prior non-ambulatory studies suggested. Kinematics were recorded in 46 healthy knees during normal-speed walking using the point cluster technique. The study found the opposite of the hypothesis: the COR was lateral in every knee tested.
The medial-pivot model of knee motion — derived from cadaver dissection, passive flexion studies, and slow-speed fluoroscopy. Became embedded in TKR design philosophy. Several implant systems were engineered to reproduce medial pivoting, assuming this reflected natural function.
This paper shows that assumption is wrong for the activity patients do most: walking. The COR is lateral during gait, meaning implants constrained to medial pivoting may actually work against normal ambulatory kinematics.
When evaluating TKR designs or counseling patients about implant selection, recognize that kinematic data from non-ambulatory or slow-speed studies cannot be extrapolated to gait. An implant that performs well in a fluoroscopy lab at 0.3 m/s may behave very differently during community ambulation.
The clinical pearl: knee kinematics are activity-specific. A design that restores medial pivot for squatting must also permit lateral pivot for walking. And these are not the same constraint.
This study tested whether the knee's center of rotation (COR) in the transverse plane sits on the medial side during walking, as prior non-ambulatory studies suggested. Kinematics were recorded in 46 healthy knees during normal-speed walking using the point cluster technique. The study found the opposite of the hypothesis: the COR was lateral in every knee tested.
The medial-pivot model of knee motion — derived from cadaver dissection, passive flexion studies, and slow-speed fluoroscopy. Became embedded in TKR design philosophy. Several implant systems were engineered to reproduce medial pivoting, assuming this reflected natural function.
This paper shows that assumption is wrong for the activity patients do most: walking. The COR is lateral during gait, meaning implants constrained to medial pivoting may actually work against normal ambulatory kinematics.
When evaluating TKR designs or counseling patients about implant selection, recognize that kinematic data from non-ambulatory or slow-speed studies cannot be extrapolated to gait. An implant that performs well in a fluoroscopy lab at 0.3 m/s may behave very differently during community ambulation.
The clinical pearl: knee kinematics are activity-specific. A design that restores medial pivot for squatting must also permit lateral pivot for walking. And these are not the same constraint.