The Torque-Velocity Relationship and Second ACL Injury Risk

Area of Science:

• Orthopedic surgery
• Sports medicine
• Biomechanics

Background:

• Anterior cruciate ligament (ACL) injury leads to a higher risk of reinjury, even after surgical reconstruction (ACLR).
• The expected inverse relationship between muscle contraction velocity and torque production is altered post-ACLR.

Purpose of the Study:

• To assess the prognostic capability of the torque-velocity relationship in predicting subsequent ACL injuries in patients recovering from primary ACLR.

Main Methods:

• A descriptive laboratory study involving 579 primary unilateral ACLR patients (average 6.9 months post-surgery).
• Isokinetic knee extension at 90°/s and 180°/s was performed bilaterally to calculate the torque-velocity relationship.
• Reinjury outcomes were tracked for a minimum of 2 years post-surgery via phone calls and medical record reviews.

Main Results:

• Approximately 14.0% of patients experienced reinjury, with similar rates across sexes and graft types.
• A 1 Nm/kg increase in quadriceps torque-velocity relationship correlated with higher odds of reinjury (OR: 3.52, P=0.045).
• Each additional year of age was associated with a 6% decrease in reinjury risk (OR: 0.94, P<0.01).

Conclusions:

• The quadriceps torque-velocity relationship effectively predicts subsequent ACL injury post-ACLR, outperforming single-velocity assessments.
• Increased patient strength may influence return-to-sport decisions, potentially increasing exposure to risk.
• Clinicians should consider enhanced surveillance for strong, young patients and integrate additional risk factors for improved reinjury prediction.