Selfe J.,Richards J., Thewlis D., Kilmurray S. The biomechanics of step descent under different treatment modalities used in patellofemoral pain Gait and Posture 2008;27 258-263
Patellar taping was made popular and common as a treatment for patellofemoral pain after Jenny McConnell published her work in the mid 1980’s. Since then multiple effects have been attributed to patellar tape: medial shifting of the patella, stronger firing of vastus medialis obliquus (VMO), earlier firing of VMO, and improved proprioception of the knee. McConnell described applying the tape with medial glide (adding tilt or rotation as indicated on the evaluation), but effects have also been found with applying the tape in a neutral position and force.
This study assessed the effect of patellar bracing and neutral patellar tape (applied directly onto the patella, with no bias toward medial or lateral glide or tilt) on knee moment and angles in the frontal and transverse planes. Subjects performed a step-down off of a 20 cm step, with a multi-camera setup tracking reflective markers.
Compared to no intervention, the patellofemoral brace and taping led to a significant reduction in the maximum coronal and range of torsional knee angles, and the range of coronal and transverse plane knee moments was also significantly reduced. The brace was most effective in controlling frontal and transverse planes, with the tape providing small but statistically significant effects. The authors recognize that they are unable to discover the cause of the changes seen in the study, and caution that the subjects in the study were asymptomatic, and young (average 28 years) – they are working on a follow-up with subjects with knee pain.
Christopher Powers came to Duke last fall to present on lower extremity mechanics, diagnosis and treatment, and he put on a fantastic course, full of his leading research and basic and advanced biomechanical concepts. As one would expect, a part of his course involved his research on weightbearing squatting in dynamic MRI machines. The primary finding in these machines is that the patella doesn’t really shift between the femoral condyles during the squat, as it’s pretty well anchored to the tibia by the patellar tendon. There is rotation at the patellofemoral joint, but it comes primarily from the femur rotating under a fixed patella. This is the reverse of what most of us were taught, especially in relation to the mechanics that we were supposedly addressing with patellar tape. Dr. Powers used these images as support for his argument that patellar taping should be forgotten for control of the patella in patellofemoral rehabilitation. I wanted to argue with him, but felt the way some of my friends and colleagues (and patients) must sometimes feel when they argue with me: they know they’ve seen something clinically, but they don’t have the research to back it up. I wanted to argue that the tape had to have some effect, because I’ve seen it work immediate wonders for some patients (including myself when I had knee pain), while doing nothing for others. The tape has some sort of effect, even if it can’t be explained mechanically through an MRI.
Dr. Powers describes weakness of the hip leading to increased frontal and transverse plane motion with knee flexion loading to justify his treatment paradigm, and there can be little argument that this is an important aspect of diagnosis and treatment when these movement patterns are present. Given the results of this study, however, there appears to be a role for bracing in controlling some of this aberrant motion, and also for taping, albeit with a lesser impact. Hopefully studies like this and those that follow it will continue to address the proprioceptive versus mechanical aspects of patellar tape application, and help us to better understand if we can determine which subgroup of patients will best benefit from it, and for what precise purpose.
Orthopedic Physical Therapy Research 