Powers CM, Ward SR, Fredericson M, Guillet M, Hellock FG. Patellofemoral Kinematics During Weight-bearing and Non-Weight-Bearing Knee Extension in Persons With Lateral Subluxation of the Patella: A Preliminary Study. J Orthop Phys Ther 2003, 33: 677-685.
Patellofemoral complaints are a common orthopedic problem. The symptoms and the resulting functional impairments are often difficult to eliminate. One of the challenges in treating these patients / clients lies in the fact that patellofemoral joint mechanics are complex. Much of the complexity comes from the great variability produced by the context of the movement. Failure to take into account the actual activity that produces the dysfunction will prevent movement specialists from finding successful interventions.
The study by Powers and his colleagues utilized dynamic MRI to look at the kinematic relationships between the patella and the femur during knee extension. The contextual difference that provided the basis of comparison was non-weight-bearing extension (NWBE) versus weight-bearing extension (WBE). Six subjects diagnosed with patellofemoral pain and lateral subluxation of the patella participated in the study. The authors looked at lateral displacement of the patella and patellar tilt (patella relative to femur). The rotations of the patella and femur were also measured relative to the three-dimensional space.
Some of the important results were that the lateral displacement was greater during NWBE when compared to WBE. Patella rotation was also greater in NWBE. The decrease in abnormal patella position in weight-bearing should be very encouraging to practitioners of Applied Functional Science®. Possibly the most important finding was that internal rotation of the femur was greater during WBE. So why does this matter for function? Since most knee extension (and potential dysfunction) occurs during weight-bearing function, we all need to be pay close attention to the rotation of the femur, particularly in the transverse plane.
In the late 1980’s, Dr. Gary Gray utilized a metaphor of the track and the train to represent a new way of thinking about patellofemoral problems. If a train is rocking to the side, or even worse leaves the track, in the majority of cases, the engineers will go out and fix the track. Occasionally it is the train’s fault, but the train’s job is to stay within the rails. In human function, the patella does respond to the pull of the quadriceps, but it is influenced more by the femur (alignment of the track) and motion of the hip, knee, ankle, foot and spine (the joints that influence the motion of the track). In functional movement, the track is moving more than the train.
If the motion of the femur (track) is the problem during weight-bearing, as highlighted in this study, then our treatments should be directed at influencing the joint motions to normalize patellofemoral mechanics utilizing weight-bearing movements. In order to understand what joints are contributing to the abnormal motion of the femoral track, movement specialists need a system to evaluate all these joints while they work together. 3DMAPS® (3D Movement Analysis & Performance System) provides the Analysis Movements to do just that. Is the femoral track moving too much? Is the femoral track moving to little? Is the femoral track moving in the wrong direction?
A specific example could be left side patellofemoral pain during a 3DMAPS® Right Same Side Rotational Chain Reaction® analysis movement. While observing the movement, the practitioner might notice that the left subtalar joint does not evert well compared to the right subtalar joint during the Left Same Side Rotational Chain Reaction® movement. Looking above the knee, the left hip might demonstrate limited external rotation. Either of these joint limitations will alter the biomechanics of the patellofemoral joint.
In the first case, the limited subtalar eversion will block internal rotation of the lower leg. While the rotational lunge of the right foot drives the femur to internally rotate. This increases the pressure of the lateral femoral condyle against the patella. In the second case, the limited left hip joint external rotation will result in increased internal rotation of the femur. The rotational lunge of the right foot causes the pelvis to rotate to the right. With restricted external rotation of the left hip, the left femur will be driven into excessive internal rotation. Again, this causes the lateral patellofemoral pressure to increase.
Not only will the 3DMAPS® transverse plane movements identify the problem, but can specify which joint motion (or both) is causing the increase in pressure between the femur and patella. Assessing the subtalar or hip motion in isolation on a table will not provide this information to the movement practitioner.