The association between patella alta and structural features of osteoarthritis on MRI: The Multicenter Osteoarthritis (MOST) Study

Abstract

Patella alta (PA) is present when the patella position is high relative to the femoral trochlea, and is a known risk factor for patellar dislocation and anterior knee pain in young persons. PA is defined as present when the Insall‐Salvati ratio (ISR), length of the patellar tendon (LT) divided by length of the patella (LP), is = 1.2. The purpose of this study was to determine, in middle aged and older persons at risk for knee osteoarthritis, the association between PA and patellofemoral joint (PFJ) cartilage morphology and bone marrow lesions (BMLs). We measured the ISR on the lateral radiograph in 443 subjects from a cohort study of persons aged 50‐79 years. Cartilage morphology and BMLs were graded on MRI using a semi‐quantitative scale (0‐6, 0‐3 respectively, with 0 representing absence of pathology) in the medial and lateral PFJ. Using logistic regression, we determined the association between the ISR and cartilage morphology and BMLs, adjusting for age, sex, and BMI. The mean ISR was 1.095 and 113 subjects' (26%) ISR was = 1.2. Compared with subjects who did not have PA, those with PA had 1.82 (95% CI 1.26, 2.63) and 2.38 (1.59, 3.58) times the odds of lateral PFJ cartilage damage and BMLs, respectively. We are currently investigating the biomechanical mechanism for the changes seen in bone and cartilage in subjects with PA. This research was supported by the NIH and Arthritis Foundation.Grant Funding SourceNIH and Arthritis Foundation