The effect of a simulated knee joint effusion on postural control in healthy subjects.

OBJECTIVE

To determine the effects of a simulated knee joint effusion on center of pressure (COP) path and mean power frequency (MPF) during standing.

DESIGN

Quasi-experimental design.

SETTING

Sports injury research laboratory in a university setting.

PARTICIPANTS

Twenty healthy volunteers, 10 of whom (age, 20.1+/-2.4y; height, 168.0+/-8.1cm; weight, 70.4+/-13.3kg) were assigned to an effusion group and 10 of whom (age, 25+/-3.8y; height, 169.4+/-8.9cm; weight, 74.7+/-7.7kg) were assigned to a control group.

INTERVENTIONS

COP data were collected before and after a 60-mL injection of sterile saline into the knee joint space.

MAIN OUTCOME MEASURES

COP path and mediolateral and anteroposterior MPF.

RESULTS

COP path decreased after the effusion (pre-effusion mean, 92.2+/-21.9cm; posteffusion mean, 77.27+/-23.0cm). No change was found within the control group for COP path (P>.05). No differences were detected before or after joint effusion when the MPF was examined (P>.05).

CONCLUSIONS

Possible explanations for the improved postural control after the effusion include additional somatosensory feedback, an augmented neural drive to the soleus, and/or increased capsular tension.