Aim. To analyze the differences in the morphological parameters of patellar position depending on the joint line obliquity, as determined using the authors’ proprietary method, in patients with medial knee osteoarthritis.

Materials and methods. Radiographic indices of patellar position were analyzed in 45 patients with medial knee osteoarthritis (n = 62 knees). The mean age of the patients was 63.84 ± 8.21 years. The following radiographic indices were calculated: Insall–Salvati, Caton–Deschamps, Grelsamer–Meadows, and Blackburne–Peel. Lateral knee radiographs were obtained with the joint flexed at 30°. The modified joint line obliquity (mJLO) angle was assessed according to the authors’ original method. An mJLO value of <177° was classified as apex distal (AD), 177–183° as apex neutral (AN), and >183° as apex proximal (AP). Statistical analysis was performed using Statistica 13 and RStudio software. The level of statistical significance was set at p ≤ 0.05.

Results. AD was identified in 43 (69.35 %) cases, AN in 16 (25.81 %), and AP in 3 (4.84 %). The mean mJLO value was 172.40 ± 4.05° in the AD group, 179.25 ± 1.81° in the AN group, and 187.33 ± 2.52° in the AP group (p < 0.00001). Significant differences were found among the groups in the mean values of the Insall–Salvati (p = 0.04), Caton–Deschamps (p = 0.01), and Blackburne–Peel (p = 0.01) indices. Signs of patella alta were more frequently observed in the AP group, whereas normal or low patellar positions predominated in the AD and AN groups. A higher patellar position was demonstrated in patients with a more proximal joint line inclination, confirmed by significant correlations: Insall–Salvati ratio (τ = +0.24, p = 0.006), Caton–Deschamps index (τ = +0.18, p = 0.04), Grelsamer–Meadows index (τ = +0.23, p = 0.009), and Blackburne–Peel ratio (τ = +0.27, p = 0.002). Predictive indicators of AD included: Insall–Salvati ratio 0.8–1.2 (OR = 4.39, CI (1.44–15.02), p = 0.009), Grelsamer–Meadows index <2 (OR = 4.39, CI (1.44–15.02), p = 0.009), and Blackburne–Peel ratio <0.8 (OR = 4.01, CI (1.31–12.89), p = 0.02). Probable predictors of AP were: Caton–Deschamps index >1.2 (OR = 833.00, CI (32.60–273970.85), p = 0.000004) and Blackburne–Peel ratio >1.0 (OR = 86.33, CI (6.90–12346.04), p = 0.0003).

Conclusions. Morphological parameters of patellar position are sensitive indicators of biomechanical alterations in medial knee osteoarthritis that depend on mJLO values. This supports their inclusion in a comprehensive radiometric program for personalized surgical planning.