The aim of the study was to characterize the features of sagittal morphology of knee joints in osteoarthritis, considering the structural variant of the joint determined by our own cluster system.

Materials and methods. A total of 100 knee radiographs from 70 patients diagnosed with osteoarthritis were analyzed. Based on the proposed classification system, morphotype I was identified in 21 patients (21.00 %), morphotype II in 38 (38.00 %), morphotype III in 29 (29.00 %), and morphotype IV in 12 patients (12.00 %). The following radiographic parameters were assessed: posterior distal femoral angle (PDFA), posterior condylar offset ratio (PCOR), posterior tibial slope (PTS), tuberosity-modified tibial slope (TMTS), and tibial tuberosity inflection angle (TTIA). Statistical analysis was performed using Statistica 13 software. Statistical significance was defined at p ≤ 0.05.

Results. The mean PDFA was 84.98 ± 5.62°. Mean values across morphotypes were: morphotype I – 89.27 ± 1.79°, morphotype II – 87.20 ± 4.50°, morphotype III – 83.11 ± 4.33°, and morphotype IV – 75.43 ± 2.64° (p < 0.00001). The mean PCOR was 0.44 ± 0.08. The index value in patients with morphotype I was 0.45 ± 0.05, morphotype II – 0.44 ± 0.10, morphotype III – 0.45 ± 0.07, morphotype IV – 0.39 ± 0.06 (p = 0.14). The mean PTS was 9.00 ± 4.18°. The highest values were found in patients with morphotype I – 11.82 ± 4.00°, patients with morphotype II – 9.72 ± 4.72°, morphotype III – 7.58 ± 2.91°, and morphotype IV – 5.86 ± 1.46° (p = 0.01). The average TMTS was 36.48 ± 6.28°. The angle value in patients with morphotype I was 35.36 ± 3.78°, morphotype II – 34.92 ± 7.17°, morphotype III – 37.45 ± 5.78°, morphotype IV – 41.14 ± 5.52° (p = 0.045). The mean TTIA was 160.54 ± 6.81°: in individuals with morphotype I – 157.91 ± 8.81°, morphotype II – 158.62 ± 5.90°, morphotype III – 162.74 ± 6.07°, and morphotype IV – 165.57 ± 4.31° (p = 0.008). A significantly higher likelihood of morphotype III was observed in patients with PDFA values 79–87° (OR = 5.66, 95 % CI: 1.71–18.68, p = 0.003). A higher probability of morphotype II development was associated with PCOR values >0.44 (OR = 3.34, 95 % CI: 1.06–10.50, p = 0.03). The presence of PTS values > 8° increases the odds of morphotype I formation (OR = 6.43, 95 % CI: 1.22–33.95, p = 0.01).

Conclusions. Given the identified morphotype-specific differences in sagittal knee joint morphology in osteoarthritis, further studies are needed to justify a personalized approach to orthopaedic surgical planning.