Functional changes of the quadriceps femoris muscle in patients with osteoarthritis of the knee

In osteoarthritis (OA) of the knee, arthrogenous muscle inhibition (AMI) is considered to be one of the reasons of quadricep muscle weakness. Its infl uence on functional impairment such as gait alterations, however, still rem ains unclear. Fourty-seven patients with knee OA (mean age 64+/-5.2 years, 36 women, II m en) and 47 age- and gender-matched healthy controls were investigated for v oluntary activation (VA) and maximum voluntary contraction (MVC) of the qua dricep muscle. In addition, these two parameters of AMI have been correlate d with the extent of gait alterations. Measurement of VA and MVC were perfo rmed by a twitch interpolation technique; for gait analysis an optoelectron ic motion analysis system (ELITE(R), Italy) was used. Quadricep MVC and VA were significantly lower in OA than in control knees. Moreover, in addition to reduced walking velocity and step cadence, gait an alysis revealed significantly lower stance phase reextension angles in OA p atients (mean 2.7 degrees+/-2.6) than in control knees (mean 10.7 degrees+/ -4.9). Hereby, in OA knees there was a significant correlation between MVC and VA deficits and the reduction of re-extension angles. The work shows that knee OA is characterized by severe alterations of the q uadricep motor function due to arthrogenous muscle inhibition. Hereby, quad ricep AMI represents one major reason for functional impairment in knee OA.