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bibliography * The PainScience Bibliography contains plain language summaries of thousands of scientific papers and others sources, like a specialized blog. This page is about a single scientific paper in the bibliography, Pattyn 2011.

Vastus medialis 9% smaller in patients with patellofemoral pain

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Pattyn E, Verdonk P, Steyaert A, Vanden Bossche L, Van den Broecke W, Thijs Y, Witvrouw E. Vastus Medialis Obliquus Atrophy: Does It Exist in Patellofemoral Pain Syndrome? Am J Sports Med. 2011 Apr. PubMed #21487120.
Tags: etiology, biomechanics, patellar pain, running, anatomy, pro, arthritis, aging, pain problems, knee, leg, limbs, overuse injury, injury, exercise, self-treatment, treatment

PainSci summary of Pattyn 2011?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided at the bottom of the page, as often as possible. ★★★★☆?4-star ratings are for bigger/better studies and reviews published in more prestigious journals, with only quibbles. Ratings are a highly subjective opinion, and subject to revision at any time. If you think this paper has been incorrectly rated, please let me know.

It is an article of faith for many professionals that the inner portion of the quadriceps muscle group (VMO) is weak and atrophied in patients with patellofemoral pain, “despite very little objective evidence” according to this paper. For the first time, researchers used MRI to measure the size of the vastus medialis obliquus muscle in patients with and without patellofemoral pain syndrome, and found that it was 9% smaller in PFPS patients. There was a 4% chance that the results are coincidental — a statistically significant result, but only just — and of course it is “not clear whether this atrophy is a result or a cause of PFPS.” However, that wise disclaimer is contradicted by the following statement that VMO is a “contributing factor in PFPS” — a troubling inconsistency in the paper’s abstract.

original abstractAbstracts 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.

BACKGROUND: Quadriceps atrophy and in particular atrophy of the vastus medialis obliquus (VMO) muscle have been frequently related with patellofemoral pain syndrome (PFPS), despite very little objective evidence.

HYPOTHESIS: Patients with PFPS exhibit atrophy of the VMO in comparison with healthy controls.

STUDY DESIGN: Case-control study; Level of evidence, 3.

METHODS: Forty-six patients with PFPS and 30 healthy control persons with similar age, gender, body mass index, and activity index distributions underwent magnetic resonance imaging (MRI) of the quadriceps. The muscle size was determined by calculating the cross-sectional area of the total quadriceps and its components.

RESULTS: The cross-sectional area (CSA) of the VMO was significantly smaller in the PFPS group than in the control group (16.67 ± 4.97 cm(2) vs 18.36 ± 5.25 cm(2)) (P = .040). A tendency was noted for a smaller total quadriceps CSA for the PFPS patients at midthigh level (66.99 ± 15.06 cm(2) vs 70.83 ± 15.30 cm(2)) (P = .074).

CONCLUSION: This is the first study to examine VMO size in PFPS patients by MRI. Patients with patellofemoral problems exhibited atrophy of the VMO. Although it is not clear whether this atrophy is a result or a cause of PFPS, the results of this study do show that atrophy of the VMO is a contributing factor in PFPS. Longitudinal, prospective studies are needed to establish the cause-effect relation of VMO atrophy and PFPS.

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