Roentgenographic and clinical findings of patellofemoral osteoarthrosis. With special reference to its relationship to femorotibial osteoarthrosis and etiologic factors.

In order to determine definitive clinical and roentgenographic findings of patellofemoral osteoarthrosis (PF-OA) and the etiologic factors of this disease as well as its relationship to femorotibial osteoarthrosis (FT-OA), 108 knees having moderate to severe PF-OA with or without FT-OA were investigated. Pain and disabilities of activities of daily living (ADL) due to PF-OA most likely appeared during movements requiring deep flexion of the knee. Roentgenographic findings revealed a great majority of the disease occurred on the lateral side of the PF joint, both in cases of PF-OA alone and in PF-OA combined with FT-OA. There was no relationship between the degree of PF-OA advancement determined by roentgenographic findings and that of ADL disabilities. PF-OA and FT-OA seemed to be caused by different etiologic factors, because the degrees of involvement of the PF and FT joints were not correlated with each other in the cases of PF-OA combined with FT-OA. Since a clear history of dislocation or subluxation of the patella was noted in 18% of PF-OA (this figure increased to 28% if limited to the cases affected with PF-OA alone), and since roentgenographic findings also agreed with this evidence, dislocation or subluxation of the patella seemed to be one of the causes of PF-OA.