In Vivo Fluoroscopic Analysis of the Normal Human Knee

Abstract

The objective of the current study was to use fluoroscopy and computed tomography to accurately determine the three-dimensional, in vivo, weightbearing kinematics of five normal knees. Three-dimensional computer-aided design models of each subject's femur and tibia were recreated from the three-dimensional computed tomography bone density data. Three-dimensional motions for each subject then were determined for five weightbearing activities. During gait, the lateral condyle experienced -4.3 mm (range, -1.9--10.3 mm) of average motion, whereas the medial condyle moved only -0.9 mm (range, 3.4--5.8 mm). One subject experienced 5.8 mm of medial condyle motion. On average, during deep flexion activities, subjects experienced -12.7 mm (range, 1.4--29.8 mm) of lateral condyle motion, whereas the medial condyle motion only was -2.9 mm (range, 3.0--9.0 mm). One subject experienced 5.8 and 9.0 mm of medial condyle motion during gait and a deep knee bend, respectively leading to the occurrence of a lateral pivot motion. During the deep flexion activities, the subjects experienced significantly more axial rotation (> 13 degrees) than gait (< 5 degrees). During all five activities, the lateral condyle experienced significantly more anteroposterior translation, leading to axial rotation of the tibia relative to the femur.

In Vivo Kinematics after a Cruciate-substituting TKA

“…Our data show subjects experienced PFR of their lateral condyle (mean 23 mm) and a lesser amount of PFR of their medial condyle (mean 14 mm) during a loaded deep knee bend. We observed greater medial condyle PFR than previously reported for the normal knee [23,25,29], leading to similar axial rotation patterns, but lower in magnitude than that of the normal knee (10.8°for the patients in this study versus 16.8°in the native knee). This greater medial PFR as compared with the normal knee raises concerns because it potentially can overload the medial structures of the knee.…”

“…This is supported with findings from fluoroscopy, studies using in vitro analyses, and those using external markers associated with gait laboratory systems [1, 2, 4, 8-10, 12, 13, 16, 18, 19, 21, 22, 24, 25, 34-37]. With increasing knee flexion, the normal knee reportedly experiences more posterior motion of the lateral condyle leading to internal rotation of the tibia with respect to the femur [18,22,25]. In contrast to the normal knee, in vivo kinematic analyses suggest subjects undergoing TKA often experience a motion pattern opposite the normal knee where the condyles slide in the anterior direction with increasing knee flexion [2,8,9,24,28,31,[34][35][36][37].…”

“…Komistek et al reported the lateral condyle achieved more posterior motion than the medial condyle, 19.2 mm and 3.4 mm, respectively, with increasing knee flexion during a deep knee bend [25]. They also reported the occurrence of intersubject variability.…”

“…Numerous kinematic analyses of the normal knee have documented greater mean posterior motion of the lateral condyle relative to the medial condyle, leading to a mean internal rotation of the tibia with progressive knee flexion [9,15,23,25,27,29]. Komistek et al reported the lateral condyle achieved more posterior motion than the medial condyle, 19.2 mm and 3.4 mm, respectively, with increasing knee flexion during a deep knee bend [25].…”

Abnormal Axial Rotations in TKA Contribute to Reduced Weightbearing Flexion

“…Because our goal for this study was to determine if axial rotation patterns affected weightbearing knee flexion, two distinctly different bounds were chosen. The first bound represented a normal rotation greater than 15°because the normal knees in our previous studies had at least 15°of axial rotation [5,9]. The second bound represented reverse rotation, which was chosen to be at least À3°to ensure a clear distinction from no rotation.…”