Does the Position of the Patella Really Matter in Patellofemoral Pain?Patients with patellofemoral pain (PFP) may have a laterally positioned patella (knee cap). If the patella doesn't track up and down over the knee correctly, then the surface of the joint is overloaded. Uneven wear of the articular (joint) surfaces may lead to PFP.
There's only one test reported so far that can be used to reliably measure patellar position. And studies are not consistent in their findings when using this test. Some find a difference in patellar position in patients with PFP and some don't. Whether or not a laterally placed patella really leads to PFP remains a topic of debate.
In this study, 12 female patients with PFP were compared to 12 women matched by age and body mass without PFP (control group). Measurements of the patella position were made by one (experienced) physical therapist. The McConnell method of measurement was used (and described). An independent examiner repeated the measurements.
Everyone in both groups had a laterally displaced patella. The PFP group was significantly more lateral than the control group. The results confirm that patients with PFP have a laterally positioned patella.
And the study confirms this test is reliable and valid. When experienced therapists administer the test, the results are consistently the same. Training and experience using the McConnell method may be needed for accurate assessment of patellar position.
But we still don't know for sure that this altered position is what causes PFP. There is general agreement that a laterally positioned patella is not normal. This is true even when everyone in both groups had a positive test result. Unless the patella is positioned centrally, there is an abnormal loading pattern of the patellofemoral joint.
More study is needed in this area. The first step remains to find an accurate test that can be used reliably by many researchers. Studies such as this one move us in the right direction.
Lee Herrington, PhD, MSc, MCSP, CSCS. The Difference in a Clinical Measure of Patella Lateral Position Between Individuals with Patellofemoral Pain and Matched Controls. In Journal of Orthopaedic & Sports Physical Therapy. February 2008. Vol. 38. No. 2. Pp. 59-62.
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