The effects of knee effusion on quadriceps strength and knee intraarticular pressure.

The purpose of this study was to determine the effect of varied amounts of effusion on quadriceps strength and knee intraarticular pressure (IAP) during active knee movement. Five subjects had 60 ml of saline, in 20 ml increments, infused into the right knee. Quadriceps strength and knee IAP were continuously measured at each level of effusion, while the subject performed isokinetic knee exercises. A control group of five subjects performed the same exercises, but with no saline infusion. No significant changes in quadriceps strength were seen in the control group. In the experimental group, quadriceps strength decreased as the amount of effusion increased, and increased following aspiration. The greatest decrease in strength occurred at those knee positions where IAP was highest (full flexion and extension). Results of this study indicate that quadriceps strength is diminished and IAP markedly increased when an effused knee is exercised.