Patellofemoral kinematics during knee flexion-extension: An in vitro study

Abstract

The purpose of this work was to obtain kinematics data for the normal human patellofemoral joint in vitro. Eight fresh-frozen cadaver knees were used. The heads of the quadriceps were separated, and the knees mounted in a kinematics rig. The femoral axis was aligned with an electromagnetic transmitter. The six heads of the quadriceps, including vasti medialis and lateralis obliquus, were loaded via cables according to their physiological cross-sectional areas and orientations. Magnetic trackers were mounted on the patella and tibia. The knee was flexedextended against the extending muscle action, and patellar tracking was measured in six degrees of freedom. As the knee flexed, the patella flexed by 0.7 times the tibiofemoral flexion angle. It also translated medially 4 mm to engage the trochlear groove at 208 knee flexion, then translated to 7 mm lateral by 908 knee flexion. The patella tilted progressively to 78 lateral by 908 knee flexion, and patellar medial-lateral rotation was usually less than 38. This is believed to be the first set of patellar tracking data obtained in both flexion and extension motion while the patella was acted on by a full set of quadriceps muscle tensions acting in physiological directions. These data may be used in future studies of the effects of pathologies on patellar tracking. ß

Three‐dimensional patellar motion at the natural knee during passive flexion/extension. An in vitro study

“…For the first time, the present study reports patellar motion with respect to both the femur and tibial reference frames, from a large population size, for a large flexion/extension arc, and according to current international recommendations. The results reported concur with comparable reports from the literature, [9][10][11]15,16,18,34 but are definitely more robust and consistent. All patterns were found to be generally repeatable intra-and interspecimens.…”

“…The analysis of PFJ translations is of clinical relevance because these allow the identification of a likely patella alta/baja and excessive medial/lateral translation. 11,18 In the present study, during TFJ flexion, the patella moves posteriorly, distally, and laterally with respect to the femur. Additional information can be given by the analysis of patellar translation along the tibial anatomical axes, although proximodistal translation is of clinical interest 35 by providing information about patella alta/baja and tightening of the patellar tendon.…”

“…10,13 In only four studies 9,10,18,20 the articular convention for the description of PFJ motion was the same as that of the present study; not in a single the patellar anatomical reference frame definition was the same as that of the present study. In addition, in these studies results were reported respectively from seven, one, eight, and four knee specimens, by magnetic sensors with 0.58 and 1.0 mm accuracy, and in a 0-908 TFJ flexion range only.…”

“…A number of studies, both in vitro [9][10][11][12][15][16][17][18][19][20] and in vivo, [21][22][23][24][25][26][27][28] have dealt with the identification of normal patellar motion, but differences in the accuracy of the measurement system used, range of knee motion examined, magnitude and direction of the load applied, and articular and anatomical conventions, hinder a thorough comparison of the results. 10,13 In only four studies 9,10,18,20 the articular convention for the description of PFJ motion was the same as that of the present study; not in a single the patellar anatomical reference frame definition was the same as that of the present study.…”

“…10,13 For this goal, patellar motion must be tracked in all six degrees of freedom, thus overcoming the traditional twodimensional X-ray based views. 14 A number of studies, both in vitro [9][10][11][12][15][16][17][18][19][20] and in vivo, [21][22][23][24][25][26][27][28] have dealt with patellar tracking by different methodological approaches and measuring devices. Among them, magnetic resonance and X-ray stereo-photogrammetry do not allow the acquisition of natural and continuous movements in a large range of knee positions.…”