Inhibition of the quadriceps muscles in patients with anterior knee pain

The present study was aimed at determining muscle inhibition (MI) and knee extensor moments in 42 subjects with unilateral anterior knee pain syndrome. The results were compared to a normal, healthy population with no history of knee injury. Also, the effects of 1 week of a nonsteroidal anti-inflammatory drug (NSAID) on MI and knee extensor moments were tested in a randomized controlled trial. At baseline, the involved leg showed significantly higher MI than the noninvolved leg. In both legs, MI was significantly higher and knee extensor moments lower than the corresponding values of the nonimpaired subjects. There was a direct relationship between knee pain during testing and the extent of MI. Higher MI, in turn, was associated with lower knee extensor moments. The study demonstrated significant MI in the quadriceps muscles of the involved and noninvolved legs of subjects with unilateral anterior knee pain syndrome. The results indicate that the noninvolved leg cannot be considered a normal control for a contralateral injury. NSAIDs did not affect MI or knee extensor moments, despite significantly reducing pain. This finding suggests that factors other than pain are responsible for the MI observed in this specific subject population, or that after removal of pain, more time is required to fully restore muscle function.