Anterior cruciate ligament deterioration correlates with patella osteoarthritis

The correlation between anterior cruciate ligament (ACL) condition and patella osteoarthritic (OA) changes has not been well reported. The aim of this study was to reveal the correlation between ACL deterioration and the morphology of OA changes in the patella. The hypothesis was that significant correlation between ACL deterioration and patella OA morphology would be revealed in this study.

Two hundred ninety-one cadaveric knees from 151 cadavers were included in this study with a median age of 83 years (54-98). Knees were opened with a sub-vastus approach and the ACL condition was classified as intact or deteriorated. Patella OA lesions were classified using Han's method: type 1, no or minimal lesion; type 2, medial facet lesion without involvement of the ridge; type 3, lateral facet lesion without involvement of the ridge; type 4, lesion involving the ridge only; type 5, medial facet lesion with involvement of the ridge; type 6, lateral facet lesion with involvement of the ridge; and type 7, global lesion. OA depth evaluation was performed following Outerbridge's classification. Statistical analysis of the collected data was performed using generalized estimating equations (GEE).

The ACL was intact in 277 knees and deteriorated in 14 knees. Patella OA lesions were observed as follows: type 1, 29%; type 2, 15%; type 3, 2%; type 4, 12%; type 5, 18%; type 6, 2%; and type 7, 22%. Outerbridge's classification of over grade 2 OA depth was observed in 73.5% of subjects. When patella OA was divided into types 1-4 and types 5-7, ACL deterioration was correlated with the occurrence of type 5-7 patella OA [OR 6.44, 95%CI 2.27-18.25, p = 0.000]. When patella OA was divided into types 1-6 and type 7, ACL deterioration was correlated with the occurrence of type 7 patella OA [OR 6.02, 95%CI 2.57-14.09, p = 0.000]. When patella OA depth was divided into grades 1-3 and grade 4, ACL deterioration was highly correlated with the occurrence of grade 4 patella OA [OR 9.31, 95%CI 2.96-29.33, p = 0.025].

ACL deterioration is a strong risk factor of wider and deeper OA changes in the patella. For clinical relevance, subjects with ACL tear should be aware of the progression of patella OA.