The Association between Knee Osteoarthritis and Changes in the Achilles Tendon: A Cross-sectional Study

Aim: To explore the association between knee osteoarthritis (OA) and morphological changes in the Achilles tendon.

Study Design: Pilot cross-sectional study.

Place and Duration of the Study: Rheumatology Unit, Barzilai Medical Center, Ashkelon, Israel. Study took place during 2014.

Methodology: A sample of 56 knee OA patients was recruited. Demographic data, sonographic evaluation of the femoral cartilage thickness, Achilles tendon thickness and Western Ontario and McMaster Osteoarthritis (WOMAC) scores, were collected. The associations between the femoral cartilage thickness, WOMAC parameters, and Achilles tendon thickness were tested by Pearson’s correlation and linear regression analyses.

Results: The Achilles tendon thickness of the non-(or less)-symptomatic side, significantly negatively correlated with the cartilage thickness of the symptomatic (r=-0.292, P=0.029) or non-(or less)-symptomatic (r=-0.319, P =0.017) side. These associations remained significant after adjustment for age and BMI in the linear regression analyses (β=-0.284, P =0.049 and β=-0.309, P =0.026, correspondingly). The WOMAC total score showed a significant positive correlation with the Achilles tendon thickness of the symptomatic side (r=0.389, P =0.003), remaining significant after adjustment for age, BMI and cartilage thickness (β=0.400, P =0.007).

Conclusions: Previous studies have shown that soleus and gastrocnemius muscles contribute to knee stabilization. Stress on the muscles used to stabilize the osteoarthritic knee may cause structural changes in the Achilles tendon. Further studies are needed to corroborate the association between the Achilles tendon thickness and knee OA. We suggest considering an assessment of the Achilles tendon as part of the knee OA evaluation.