Variations in patellar position according to knee joint morphotype in patients with osteoarthritis

Background. Patellar position relative to knee joint morphotype is clinically relevant. The purpose was to characte­rize patellar position features in patients with knee osteoarthritis, considering morphological joint variants. Materials and ­me­thods. Radiographs of 100 patients (mean age 63.56 ± 8.10 years) with medial knee osteoarthritis were analyzed. Morphotype I was identified in 21.0 %, morphotype II in 38.0 %, morphotype III in 29.0 %, morphotype IV in 12.0 % of cases. Patellar position was assessed using Insall-Salvati, Caton-Deschamps, Grelsamer-Meadows, Blackburne-Peel indices. Statistical significance was set at p ≤ 0.05. Results. Mean Insall-Salvati index was 1.11 ± 0.05 in morphotype I, 1.29 ± 0.38 in morphotype II, 1.32 ± 0.25 in morphotype III, 1.40 ± 0.14 in morphotype IV (p = 0.009). Caton-Deschamps index was 0.77 ± 0.14 in morphotype I, 0.74 ± 0.23 in morphotype II, 0.78 ± 0.24 in morphotype III, and 1.05 ± 0.16 in morphotype IV (p = 0.02). Mean Grelsamer-Meadows index was 1.84 ± 0.12 in morphotype I, 1.86 ± 0.46 in morphotype II, 1.86 ± 0.44 in morphotype III, and 2.41 ± 0.33 in morphotype IV (p = 0.009). Blackburne-Peel ratio was 0.64 ± 0.09 in morpho­type I, 0.59 ± 0.23 in morphotype II, 0.74 ± 0.24 in morphotype III, and 0.98 ± 0.14 in morphotype IV (p = 0.001). Blackburne-Peel index < 0.8 was associated with a higher likelihood of morphotype II (OR = 9.8; 95% CI: 1.9–49.2; p = 0.0007). Increased odds of morphotype III were associated with Insall-Salvati index > 1.2 (OR = 4.7; 95% CI: 1.4–16.0; p = 0.007), Blackburne-Peel 0.8–1.0 (Odd Ratio (OR) = 4.4; 95% CI: 1.2–17.0; p = 0.03). Caton-Deschamps > 1.2 and Blackburne-Peel > 1.0 were associa­ted with greater odds of morphotype IV (OR = 21.6; 95% CI: 1.6–297.4; p = 0.02, and OR = 23.1; 95% CI: 3.3–160.1; p = 0.001, — respectively). Conclusion. Therefore, in morphotypes I and II, patellar position alterations were primarily associated with pathological changes in the proximal tibia, whereas in morphotypes III and IV, they were predominantly linked to patellofemoral joint involvement.