Association between medial knee joint bone morphology and popliteal cyst: a retrospective MRI-based analysis

Baker's cyst, or popliteal cyst, is a common knee condition associated with osteoarthritis and rheumatoid arthritis. While previous studies have explored the cyst's relationship with soft tissue abnormalities, the connection between popliteal cysts and medial knee bone morphology remains unclear. This study aims to assess the association between anatomical bone structures of the medial knee joint and popliteal cyst presence using magnetic resonance imaging (MRI).

A retrospective analysis was conducted on 100 patients who underwent MRI for knee pain between June and December 2021. Group 1 (n = 50) consisted of patients with Baker's cysts, and group 2 (n = 50) included those without cysts. MRI measurements included medial condyle width, condyle length, distal and posterior articular diameters, medial tibial plateau depth, and tibial slope. Cyst dimensions and volume were measured. Statistical analyses, including Pearson correlation and chi-square tests, were performed, with significance set at p < 0.05.

No significant differences in medial knee bone morphology were found between groups (p > 0.05). However, popliteal cyst size was positively correlated with age (p = 0.016, r = 0.339 and p = 0.020, r = 0.328, respectively). Higher Kellgren-Lawrence grades were also associated with cyst presence (p = 0.001). Gender correlated with knee measurements, showing smaller knee dimensions in women (p < 0.001).

This study found no direct association between medial knee bone morphology and the presence of popliteal cysts. However, cyst size increased with age and degenerative changes, suggesting that inflammation and joint degeneration may play a significant role in cyst development. Further studies with larger cohorts are required to validate these findings.