Reliability of the Active and Passive Knee Extension Test in Acute Hamstring Injuries

Background: Hamstring flexibility measurements are of clinical relevance for the prognosis of hamstring injury and for monitoring recovery after such injury. The active knee extension test (AKET) and passive knee extension test (PKET) are proven to be reliable in healthy subjects. Reliability has not been determined in patients with acute hamstring injuries. Purpose: The purpose of this study was to determine intertester reliability of the AKET and the PKET in patients with acute hamstring injuries. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: Fifty consecutive athletes with acute hamstring injuries confirmed with magnetic resonance imaging were included in this study. For each subject, 2 testers performed the AKET and the PKET within 5 days after injury. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable difference (MDD) were determined. Results: In the injured leg, the ICC of the AKET was 0.89 and of the PKET 0.77, the SEM of the AKET was 5.3 degrees and of the PKET 7.6 degrees, and the MDD of the AKET of the 15 degrees and of the PKET 21 degrees. Conclusion: Good intertester reliability was found for the AKET and the PKET in injured hamstrings. Thus, both tests can be reliably used to assess flexibility in injured hamstrings, despite pain and discomfort during testing.