Is proprioception altered during loaded knee extension shortly after ACL rupture?

Knee joint angle reproduction was measured without loading of the quadriceps and during concentric quadriceps contractions at 20% of maximal voluntary contraction. The threshold of movement detection was measured. The reproducibility of the methods and the effect of an acute ACL rupture < 10 wks post-injury were examined. A test-retest protocol with a 1 wk hiatus was conducted on 15 healthy subjects. Side-to-side differences were tested in 10 patients with acute ACL rupture. The test-retest protocol did not show any significant differences and yielded correlations of r=0.7-0.9 (p<0.01) and coefficients of variations of 5.7-13.0%. No side-to-side differences were detected in the ACL subjects. Quadriceps loaded; injured 3.96 +/- 2.21 , uninjured 4.7 +/- 1.23, unloaded; injured 2.85 +/- 0.56 degrees, uninjured 2.92+/-1.20 degrees. Threshold of movement detection; injured 1.48+/-0.81 degrees, uninjured 1.44+/-0.65 degrees. Therefore, it may be questioned if the ACL itself plays a major role in proprioception performance as it is commonly measured in the laboratory.