A novel method for assessing proximal tibiofibular joint on MR images in patients with knee osteoarthritis

Summary Objectives To validate a method to measure the morphological parameters of the proximal tibiofibular joint (PTFJ) in patients with knee osteoarthritis (OA). Methods 408 participants were examined in this cross-sectional subject-based study. We calculated the fibular contacting area of PTFJ (S) and its projection areas onto the horizontal plane (load-bearing area, Sτ), the sagittal plane (lateral stress-bolstering area, Sφ) and the coronal plane (posterior stress-bolstering area, Sυ). Joint space narrowing (JSN) and osteophyte was measured using radiographs. Cartilage defects, bone marrow lesions (BMLs) and cartilage volume were evaluated using magnetic resonance imaging (MRI). Results The average PTFJ fibular contacting area was 2.4 cm2 (SD, ±0.7 cm2). Intra-observer and inter-observer reliabilities of measures of PTFJ morphological parameters were excellent (≥0.90). S, Sτ and Sφ were significantly associated with JSN in the medial tibiofemoral compartment (PR: 1.40, 95% CI 1.10–1.78; PR: 1.65, 95% CI 1.25–2.18 and PR: 0.53, 95% CI 0.29–0.97, respectively). There was a significantly positive association between S, Sτ and medial and/or femoral tibial cartilage defects. S, Sτ and Sυ were significantly and positively associated with medial and/or femoral tibial BMLs (PR: 1.36, 95% CI 1.12–1.64; PR: 1.47, 95% CI 1.17–1.83; and PR: 1.39, 95% CI 1.06–1.82, respectively) after adjustment. S and Sτ were significantly and negatively associated with medial tibial cartilage volume. Conclusions This novel method to assess the morphological parameters of PTFJ in MRI is reproducible. These parameters are associated with knee radiographic and MRI-based OA-related structural abnormalities, suggesting clinical construct validity. Its predictive validity needs to be examined in future longitudinal studies.