The relationship between the angle of the trochlear groove and patella cartilage and bone morphology - a cross-sectional study of healthy adults

Objectives: Although the geometry of the trochlear groove is considered important in the pathogenesis of patellofemoral joint pathology it is unclear how the shape of the trochlear groove relates to patella morphology. This cross-sectional study investigated the relationship between the shape of the trochlear groove and patella cartilage and bone morphology in healthy adults. Methods: Two hundred and ninety-seven healthy adults aged between 50 and 79 years with no clinical history of knee pain or pathology were examined using magnetic resonance imaging (MRI). From the magnetic resonance (MR) images, the bony angles formed at the distal and proximal trochlear groove were measured, together with patella cartilage and bone volumes and patella cartilage defects. Results: After adjustment for potential confounders, there was an 8.70 mm³ (95% confidence interval (CI) 2.15, 15.26) increase in patella cartilage volume (P = 0.009), with no increased prevalence of cartilage defects (odds ratio = 0.99 (95% CI 0.96, 1.02), P = 0.35), for every 1° increase (i.e., as the angle became more flatter) at the distal trochlear groove. Moreover, there was a 53.86 mm³ (95% CI -90.26, -17.46) reduction in patella bone volume for every 1° that the angle at the distal trochlear groove became more flattened (P = 0.004). No significant association between the proximal trochlear groove angle and the patella cartilage or bone properties was observed. Conclusion: A more flattened bony angle at the distal trochlear groove was associated with increased patella cartilage volume and reduced patella bone volume, but no increased prevalence of patella cartilage defects in adults with no history of knee pain or clinical disease. These cross-sectional findings suggest that a flattened distal trochlear groove may protect against degenerative patellofemoral conditions, such as osteoarthritis, but this will need to be confirmed in a longitudinal study.