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The Pain & Therapy Bibliography, Record ID 3576 {show all records}

Patellar maltracking is prevalent among patellofemoral pain subjects with patella alta: An upright, weightbearing MRI study

added Feb 27, 13, updated May 25, 14
most detailed summaries by Paul Ingraham


This study reports that people with patellofemoral (kneecap) pain tend to have higher kneecaps, and in turn those with high kneecaps are less likely to slide evenly on the knee. This contradicts my bias and I’m a bit skeptical. The researchers were probably biased in the other direction, and expected to find abnormalities correlating with pain. They title and abstract seem crafted to show that the study proves that tracking is a factor in patellofemoral pain, and yet I think the data shows exactly the opposite.

Strangely, they didn’t measure all that many knees, just 52, and it’s easy to find what you expect in small batches of data. They don’t report just how much higher kneecaps were in the abstract, which would be natural to do if it were an impressive number, so I suspect it’s not an impressive number. Similarly, the prevalence of maltracking was allegedly a little higher in patients with pain (32% in vs. 27%), but the statistical significance of the difference was not reported — so it probably wasn’t significant. Furthermore, the presence of maltracking or patella alta in people with pain did not increase pain level.

Even if the correlation is real, it doesn’t tell us anything about cause (maybe misbehaving kneecaps cause pain, or maybe knee pain causes kneecaps to misbehave). Almost half their subject had no abnormalities at all, which is consistent with other studies (Herrington et al) showing that you can find a roughly even mix of abnormalities in everyone, whether they have pain or not.

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article in a journal
Saikat Pal, Thor F Besier, Gary S Beaupre, Michael Fredericson, Scott L Delp, and Garry E Gold
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Journal of Orthopaedic Research


The purpose of this study is to determine if patellar maltracking is more prevalent among patellofemoral (PF) pain subjects with patella alta compared to subjects with normal patella height. We imaged 37 PF pain and 15 pain free subjects in an open-configuration magnetic resonance imaging scanner while they stood in a weightbearing posture. We measured patella height using the Caton-Deschamps, Blackburne-Peel, Insall-Salvati, Modified Insall-Salvati, and Patellotrochlear indices, and classified the subjects into patella alta and normal patella height groups. We measured patella tilt and bisect offset from oblique-axial plane images, and classified the subjects into maltracking and normal tracking groups. Patellar maltracking was more prevalent among PF pain subjects with patella alta compared to PF pain subjects with normal patella height (two-tailed Fisher's exact test, p < 0.050). Using the Caton-Deschamps index, 67% (8/12) of PF pain subjects with patella alta were maltrackers, whereas only 16% (4/25) of PF pain subjects with normal patella height were maltrackers. Patellofemoral pain subjects classified as maltrackers displayed a greater patella height compared to the pain free and PF pain subjects classified as normal trackers (two-tailed unpaired t-tests with Bonferroni correction, p < 0.017). This study adds to our understanding of PF pain in two ways-(1) we demonstrate that patellar maltracking is more prevalent in PF pain subjects with patella alta compared to subjects with normal patella height; and (2) we show greater patella height in PF pain subjects compared to pain free subjects using four indices commonly used in clinics.

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