Anterior cruciate ligament-deficient potential copers and noncopers reveal different isokinetic quadriceps strength profiles in the early stage after injury.
BACKGROUND
Isokinetic muscle strength testing using the peak torque value is the most frequently included quadriceps muscle strength measurement for anterior cruciate ligament (ACL)-injured subjects. PURPOSE AND HYPOTHESES: The purpose of this study was to investigate quadriceps muscle performance during the whole isokinetic curve in subjects with ACL deficiency classified as potential copers or noncopers and to investigate whether these curve profiles were associated with single-legged hop performance. We hypothesized that quadriceps muscle torque at other knee flexion angles than peak torque would give more information about quadriceps muscle strength deficits. Furthermore, we hypothesized that there would be significant torque differences between potential copers and noncopers and a significant relationship between angle-specific torque values and single-legged hop performance.


METHODS
Cross-sectional study; Level of evidence, 3.


METHODS
Seventy-six individuals with a complete unilateral ACL rupture within the last 3 months were included. The subjects were classified as potential copers and noncopers. Isokinetic quadriceps muscle tests were performed at 60 deg/s. Mean torque values were calculated for peak torque as well as for specific knee flexion angles. The 1-legged hop and the 6-m timed hop tests were included, and symmetry indices were used.


RESULTS
The peak torque value did not identify the largest quadriceps muscle strength deficit. Rather, these were established at knee flexion angles of less than 40 degrees . There were significant differences in angle-specific torque values between potential copers and noncopers (P < .05). Moderate to strong associations were disclosed between angle-specific torque values and single-legged hop performance, but only for noncopers (r > or = .32-.58).


CONCLUSIONS
Angle-specific quadriceps muscle torque values of less than 40 degrees of knee flexion provide more information on the quadriceps strength deficits after ACL injury than the commonly used peak torque values. Interpretation of the isokinetic curve profiles seems to be of clinical importance for the evaluation of quadriceps muscle performance after ACL injury.
Eitzen
Ingrid
I
Norwegian Research Center for Active Rehabilitation (NAR), Orthopaedic Centre, Oslo University Hospital, Ullevaal, Norway. Ingrid.Eitzen@hjelp24.no
Eitzen
Thomas J
TJ
Holm
Inger
I
Snyder-Mackler
Lynn
L
Risberg
May Arna
MA
D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000503:physiopathology; D000070598:Anterior Cruciate Ligament Injuries; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology / Q000534:rehabilitation*; D008297:Male; D008875:Middle Aged; D052097:Quadriceps Muscle / Q000503:physiopathology*; D019415:Torque; D055815:Young Adult