Study design: Within-subject and between-subject cross-sectional study.
Objectives: To investigate symmetry in hop-test performance, strength, and lower extremity kinematics 6 to 9 months following anterior cruciate ligament reconstruction (ACLR).
Background: Despite the extensive body of literature involving persons following ACLR, no study has comprehensively evaluated measures of strength, lower extremity kinematics, and functional performance of functional hop tests in this population.
Methods: The subjects were 22 men (mean ± SD age, 28.8 ± 11.2 years) who had ACLR using a bone-patellar tendon-bone autograft 6 to 9 (7.01 ± 0.93) months previously and 22 healthy male controls (age, 24.8 ± 9.1 years). Participants completed a self-report questionnaire and underwent isokinetic strength testing and functional and kinematic assessment of the single-, triple-, and crossover-hop tests. Two-way analyses of variance were used to test for differences between the ACLR group and the control group, and between the 2 lower extremities of the ACLR group.
Results: Compared to the control group, the ACLR group had greater isokinetic knee extension torque deficits at all speeds (P ≤.001) and greater performance asymmetry for all 3 hop tests (P<.001). Compared to the noninvolved lower extremity, the involved lower extremity of the ACLR group exhibited less ankle dorsiflexion and knee flexion in the phases of propulsion (P ≤.014) and landing (P ≤.032). When compared to the control group, the involved lower extremity exhibited less ankle dorsiflexion in the propulsion phase (P<.001) but higher hip flexion in the landing phase (P = .014).
Conclusion: Six to 9 months following ACLR, patients continue to demonstrate functional hop and isokinetic knee extension deficits, as well as kinematic differences, during the propulsion and landing phases of the hop tests.