Purpose: Muscle atrophy is a commonly encountered problem in osteoarthritis (OA). The aim of this study was to estimate the amount of muscle atrophy and fatty degeneration of the lower leg muscles related to ankle OA by magnetic resonance imaging (MRI).
Methods: Twenty-one patients with unilateral ankle OA were included in this cohort study. Calf circumference of the affected and healthy lower leg was documented. The degree of OA was classified in conventional radiographs. The cross-sectional areas and fatty degeneration of the muscles of the lower leg were measured in bilateral MRI.
Results: We found a significantly reduced calf circumference of the affected vs. healthy leg (p = 0.016). MRI showed a significantly lower cross-sectional area of the entire lower leg musculature in OA (p = 0.013). Sub-analysis of muscle groups revealed that only the M. soleus had a significant cross-sectional area decrease (p < 0.01). All muscles showed a significant fatty degeneration (p < 0.01).
Conclusions: We conclude that unilateral ankle joint osteoarthritis leads to an overall lower leg muscle atrophy, but significant atrophy of the M. soleus. All muscles of the affected leg undergo a fatty degeneration.