Introduction Adolescent anterior cruciate ligament (ACL) injuries have increased substantially over the last two decades and some 25% will experience a re-injury following surgery, with injury rates highest among females. As such, improved return to activity metrics are imperative. Vertical jump performance is a one commonly used tool, however performance standards and the role of the injured or non-injured limb in achieving jump height is unknown for adolescent males and females. As such, the purpose of this study was to (1) assess performance in ACL injured and uninjured adolescents, and (2) assess limb contributions to this performance.

Materials and Methods Thirty-one ACL injured and thirty-eight control female adolescents, and fifteen ACL injured and twenty-five control male adolescents performed a countermovement jump (CMJ) task while whole body 3D kinematics were recorded. Maximum jump height and the maximum sagittal hip, knee, and ankle velocities were calculated. Females and males were analysed separately, while contrasts were made between limbs and injury status.

Results Jump height was 13% lower in the ACLi compared to CON, while the ACLi contralateral limb also produced greater hip, knee and ankle angular velocities compared to their injured limb in females. No difference was found in jump height between ACLi and CON, however the contralateral limb of the ACLi males had greater hip and knee extension angular velocities. Neither male nor female controls had inter-limb differences.

Conclusion ACLi adolescents shielded the injured limb to achieve similar jump performance. This leads to asymmetrical joint loading and may explain injury risk.