Thehaemophilicarthropathyaffects thefunction of theknee joint muscles. The aim of thisstudywas to investigatethe myoelectrical signal ofknee jointmusclesin different agestages during upright standing. Surface EMG (SEMG) amplitudes of quadriceps, hamstrings and gastrocnemii were measured in 191 patients with severe haemophilia A (n=164) and B (n=27) while standing on an even surface. After an age-based classification of patients into the subgroups H(A): 17-29 (n = 37), H(B): 30-39 (n = 50), HC: 40-49 (n = 61), H(D): 50-70 in years (n = 43) the clinical WFH score for the ankle and knee joint was determined. To normalize the SEMG values amplitude ratios (percentage of cumulated activity) were calculated with respect to the specific limb. With increasing age, the patient showed descriptively a deterioration of the joint situation. The extensors of the knee joint reached significantly higher absolute and percentage levels in the muscle activity with increasing age (p < 0.05). The absolute amplitude values of the Mm. gastrocnemii showed no differences in the age groups while the relative levels were decreased. The present study shows that patients with increasing age and degree of haemophilic arthropathy develop a modified control strategy during upright standing, in the form of a shift from the plantar flexors to the extensors of the knee joint.
Keywords: Haemophilia; arthropathy; knee; surface EMG; upright standing.