Abstract
Introduction and Purpose: The knee joint is a complex joint consisting of the tibiofemoral and patellofemoral joints. Morphological variations are common in the knee joint, due to the articulation of anatomically incompatible bones. These variations may lead to various pathologies, mostly in the patellofemoral joint. One of the most common pathologies and an important cause of knee pain is chondromalacia. In this study, we aimed to investigate the relationship between lateral patellar tilt angle (LPTA), lateral patellofemoral angle (LPFA), patella-patellar tendon angle (PPTA), and lateral trochlear inclination angle (LTI), which are anatomical variations in the patellofemoral joint, and patellar chondromalacia.
Materials and Methods: Cases who underwent knee magnetic resonance imaging (MRI) between June and October 2022 were analyzed retrospectively. Fifty patients with and without patellar chondromalacia were included randomly from these MRIs. Cases with a history of knee surgery, arthroscopy and high-energy trauma were excluded. Two groups were formed with and without patellar chondromalacia. LPTA, LPFA, PPTA and LTI were measured on knee MRIs. Demographic data and anatomical measurements between the two groups were evaluated with Mann-Whitney U and continuity corrected chi-square test.
Results: The median age of the patients included in the study was 45 (Interquartile Range [IQR]: 18.5). There were 58 women and 42 men. In the patellar chondromalacia group, 17 (34%) patients had low- grade chondromalacia and 33 (66%) patients had high-grade chondromalacia. The median age was 49 (IQR: 61) in the patellar chondromalacia group and 37.5 (IQR: 38) in the normal group (p<0.001). There was no statistically significant difference in gender distribution between the two groups (p=0.156). The median lateral patellar tilt angle was 6.76 (IQR: 15.15) in the patellar chondromalacia group and 6.92 (IQR: 19.25) in the normal group (p=0.610). The median lateral patellofemoral angle was 7.86 (IQR: 41.86) in the patellar chondromalacia group and 7.90 (IQR: 17.37) in the normal group (p=0.471). Median patella – patellar tendon angle was 142.96 (IQR: 32.14) in the patellar chondromalacia group and 145.87 (IQR: 27.77) in the normal group (p=0.006). The median lateral trochlear inclination angle was 19.11 (IQR: 19.30) in the patellar chondromalacia group and 20.39 (IQR: 20.16) in the normal group (p=0.127).
Discussion and Conclusion: The patellofemoral joint is an important component of the extensor mechanism. It distributes the load on the knee joint more homogeneously during extension. It has been described that anatomical differences in the patellofemoral joint can cause damage to the patellar cartilage by affecting the load distribution. We found a statistically significant difference between the groups in terms of median PPTA and median age. The median age of the patients in the chondromalacia group was higher. This may have been due to degenerative cartilage changes. The lower detection of median PPTA in the chondromalacia group indicates that the angular position of the patella may have increased the load on the patellofemoral joint, leading to cartilage damage. In conclusion, it should be kept in mind that demographic differences and anatomical variations may be a cause of patellar chondromalacia.