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chapter 11: Articular Cartilage Lesions in Patellofemoral Pain Patients

ARTICULAR CARTILAGE LESIONS IN THE PATIENT WITH CHRONIC PATELLAR TILT

The articular cartilage of a chronically tilted patella will usually experience focal over­loading. Chronic lateral tilt, related to malalignment with adaptive shortening of the lat­eral retinaculum, will concentrate loads on a lateral facet contact area that is substan­tially less than the usual contact area across the medial and lateral facets of a normally articulating patellofemoral joint. These loads may be further accentuated by a tight lat­eral retinaculum, which exerts posteriorly directed force on the patella with knee flex­ion as the iliotibial band moves posteriorly. This combination of mechanical load con­centration on the lateral facet and accentuation of the load by adaptively shortened retinaculum can have devastating effects on the patellofemoral joint and lead ultimately to the excessive lateral pressure syndrome as described by Ficat (53). Medial facet breakdown may also evolve, either by extension across the midpatella or because of chronically deficient medial facet contact pressure and excessive shear.

Tilt with subluxation (Type II malalignment) poses a slightly different problem in which lateral movement of the patella may actually permit better adaption to retinacular strain such that a patella is drawn laterally by tight lateral retinaculum rather than driven into the lateral trochlear facet. The combination of tilt and subluxation still leads to patellar cartilage degeneration in many patients (Fig. 11.44), and such patients generally experi­ence more instability of the extensor mechanism than the patient with tilt alone.

 

        

Inside Chapter 11: