Analyses of the path of instant center of rotation (PICR) can be used to infer joint-surface rolling and sliding motion (arthrokinematics). Previous PICR research has not quantified arthrokinematics during weight-bearing (WB) movement conditions or studied the association of muscle activity with arthrokinematics.
To examine tibiofemoral arthrokinematics and thigh-muscle EMG during WB and non-weight-bearing (NWB) movement.
2 x 9 repeated-measures experiment.
11 healthy adults (mean age 24 years).
Main Outcome Measures:
Tibiofemoral percentage rolling arthrokinematics and quadriceps: hamstring EMG activity.
WB percentage rolling (76.0% ± 4.7%) exceeded that of NWB (57.5% ± 1.8%) through terminal knee extension (F 8,80 = 8.99, P < .001). Quadriceps:hamstring EMG ratios accounted for 45.1% and 34.7% of the variance in arthrokinematics throughout the WB and NWB movement conditions, respectively (P < .001).
More joint-surface rolling occurs through terminal knee extension during WB movement and is associated with an increase in hamstring activity.