Association of hip shapes with knee osteoarthritis outcomes in older-adults

Abstract

Purpose: Various hip shapes may be important as a risk factor for development and progression of knee osteoarthritis, potentially due to the biomechanical link between the two joints. Therefore, this study aims to identify the relationship between hip morphology and structural and clinical osteoarthritis outcomes in the knee, in older-adults. Methods: 377 community-dwelling older-adults aged 50-80 years were studied. At baseline, dual-energy X-ray absorptiometry images of the left hip were obtained and hip shapes were described using mode scores from an 85-point statistical shape model. MRI scans were conducted at baseline and a mean follow-up of 10.7(SD:0.67) years later, to assess right knee tibial cartilage volume and bone-marrow lesions(BMLs). Knee pain was assessed using Western Ontario and McMaster Universities Osteoarthritis Index(WOMAC). Knee replacement(KR) data were obtained by data linkage to the Australian Orthopaedic Association National Joint Replacement Registry. Linear mixed-effects, log-binomial models and survival analysis were used to investigate associations between hip shape modes and knee osteoarthritis outcomes adjusting for potential confounders. Results: Ten hip shape modes were identified, describing 78% of the total shape variance in descending order from mode 01 (31% variance) to mode 10 (1.82% variance). Hip shapes with a larger greater trochanter (mode 07) were associated with less knee cartilage volume loss (β: 2.14, 95% CI: 0.07,4.21), while a shorter and narrower femoral neck shape (mode 09) was related to increased volume loss (β: -3.86, 95% CI: -6.16, -1.56). Hip shapes with a non-spherical femoral head (mode 04) were associated with an increased risk of incident BMLs (RR: 1.19, 95% CI:1.07, 1.34). Those with a longer, wider femoral neck and a larger femoral head (mode 01) had an increased risk of worsening knee pain (RR: 1.33, 95% CI: 1.09, 1.61), whereas those with a smooth curving upper femoral neck (mode 09) had a lower risk of worsening knee pain (RR: 0.78, 95% CI: 0.67, 0.90). A larger greater trochanter and wider femoral neck shape (mode 08) was associated with an increased risk of KR (RR: 1.73, 95% CI: 1.18, 2.52), while increasing acetabular coverage (mode 10) was associated with a lower risk of KR (RR: 0.54, 95% CI: 0.36,0.8). Conclusions: Hip shape variations were associated with significant MRI-based and clinical outcomes in the knee over 10.7 years, possibly due to biomechanical, lifestyle or other factors related to both joints. These results suggest that hip shape may play an important role in the onset and progression of knee osteoarthritis over time.