Changes in functional characteristics and myosin heavy chain composition in m. vastus medialis before and after arthroscopy for knee injury

The aim of this study was to investigate the influence of restriction of mo vement on the functional characteristics and myosin heavy chain composition of m. vastus medialis. The subjects of this study were 13 arthroscopically treated patients with meniscus lesions (both men and women, mean age 28 ye ars). All measurements were performed and biopsies were taken bilaterally b efore and 6 months after knee arthroscopy. Thigh girth was measured to dete rmine the degree of atrophy. A tendency towards decreased thigh girth in th e injured leg was noted. As an estimate of functional characteristics, maxi mum voluntary contraction (MVC) was measured. The MVC of the injured limb w as lower than that of the non-injured limb (mean values 548.2 +/- 54.1 and 705.4 +/- 48.2 N respectively; P < 0.05). The myosin heavy chain (MHC) comp osition was determined electrophoretically. The proportion of MHC I isoform decreased from 59.35% to 47.97% (P < 0.05).