Ankle muscle activation in people with haemophilia

Since normative surface EMG (SEMG) values for muscles acting at the knee joint are available for people with haemophilia, increasing interest is noticeable for other joints affected by haemophilic arthropathy. Adequate activity of shank muscles is an important key for appropriate postural control. The aim of this study was to determine differences in muscle activation patterns of lower leg muscles between people with and without haemophilia during upright standing. SEMG of tibialis anterior (TA), fibularis longus (FL), lateral (LG) and medial (MG) heads of gastrocnemius, and soleus (SO) muscles of both sides were recorded in 25 haemophilic patients (H) and 25 non-haemophilic control subjects (C) while standing on even ground. The Gilbert-Score was used to assign sides to major (H-MA) and minor (H-MI) affected ankle joints in H. To normalize the SEMG amplitudes, amplitude ratios (percentage of cumulated activity) were calculated. Compared to controls, TA ratios showed higher and MG reduced levels in both H groups (P < 0.01). In the H-MA subgroup of H, FL also joined the TA behaviour whereas SO had similar activation direction as MG. Although possible descending influences from the knee joints cannot be excluded, this can be interpreted as a compensational mechanism due to the severity of the orthopaedic status of the ankle, which with increasing heaviness is accompanied by reduced plantar flexion capability. However, ankle joint integrity appears to be reduced in H, with TA and MG seeming to play key roles for neuromuscular control of upright posture.