Effects of simulated vastus medialis strength variation on patellofemoral joint biomechanics in human cadaver knees

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Tags: knee, running, anatomy, IT band pain, patellar pain, tendinosis, leg, limbs, pain problems, exercise, self-treatment, treatment, overuse injury, injury, arthritis, aging

Two articles on PainSci cite Lee 2002: 1. The Complete Guide to Patellofemoral Pain Syndrome2. Patellofemoral Pain & the Vastus Medialis Myth

PainSci notes on Lee 2002:

From the abstract: “Treatment included iliotibial band stretching and patellar mobilizations that focused on stretching the lateral retinaculum. It may have been these latter treatments or strengthening of the quadriceps muscle as a whole that was responsible for the decrease in symptoms.” Indeed! This study suggests that vastus medialis muscle may have little effect on patellofemoral joint mechanism, although a study of living patients would be better than studying the dead knees of cadavers, as was done here.

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

Selective strengthening of the vastus medialis (VM) muscle is a conservative treatment used to address some patellofemoral joint (PFJ) problems. The objective of this study was to examine the effects of varying VM strength on PFJ kinematics and contact pressures and areas. We tested five fresh-frozen cadaveric knees using a custom knee jig, which permits the simulation of physiologic quadriceps loading while also allowing the VM force to be varied. PFJ kinematics were measured with a magnetic tracking device. PFJ contact pressures and areas were measured with Fuji pressure-sensitive film. For PFJ kinematics, the change in the medial-lateral and superior-inferior translation was significant at 0% of VM strength and 150% of VM strength with respect to the 100% of VM strength condition (p 0.05). The functional range of VM strength is between 75% and 125% of total VM strength. The PFJ kinematics and contact pressures were not significantly influenced by VM strength except at extreme conditions (0% of VM strength or 150% of VM strength) in human cadaveric knees.

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