Chondromalacia of the patella. Incidence, macroscopical and radiographical findings at autopsy.

In a post-mortem series of 59 persons aged 10-50 years, 91 of the 118 patellae exhibited cartilaginous changes. These changes were most common in the older age groups and usually affected the medial articular facet where they were also most extensive and most profound. Clinical and radiological assessment showed this facet to be less suited to articulation with the femur because of its convex joint surface, central ridges, and prominences. Radiography using tangential views of the entire patella and of 2 mm thick slices of the patella showed in cases with macroscopically normal cartilage a less dense bony structure medially and a denser structure laterally. Even in the presence of distinct cartilaginous changes this difference in bone density did not alter essentially. In particular, there was no definite sclerosing medially, where the changes in the cartilage were most marked. Osteophyte formation was sparse, but most common in the older age groups, and laterally. Osteophytes were seen only on patellae with cartilaginous changes.