Purpose: To examine potential deficits in muscle strength or functional capacity when comparing (1) an ACL reconstructed group to matched healthy controls, (2) the ACL reconstructed leg to the non-injured leg and (3) the non-injured leg to matched healthy controls, at the time-point of recommended sport return 9-12months post-surgery.
Methods: Sixteen patients (male-female ratio: 9:7) 9-12months post ACL reconstruction and sixteen age and sex matched healthy controls were included. Outcome measures included maximal knee extensor (KE) and knee flexor (KF) dynamometry, including measurement of rate of force development, functional capacity (counter movement jump (CMJ) and single distance hop (SDH)) and the Lysholm score.
Results: Compared to the control group, maximal KE and KF muscle strength were impaired in the ACL reconstructed leg by 27-39% and 16-35%, respectively (p<.001). Also, impairments of both CMJ (38%) and SDH (33%) were observed (p<.001). Rate of force development for KE were reduced in the ACL group compared to the control group (p<.001). Similarly, the KE and KF muscle strength, CMJ and SDH of the ACL reconstructed leg were impaired, when compared to the non-injured leg by 15-23%, 8-20%, 23% and 20%, respectively (p<.05).
Conclusion: Muscle strength and functional capacity are markedly impaired in the ACL reconstructed leg of recreationally active people 9-12months post-surgery when compared to healthy matched controls and to their non-injured leg. This suggests that objective criteria rather than "time-since-surgery" criteria should guide return to sport.
Keywords: Control group; Eccentric; Isometric and concentric muscle strength; Rate of force development.
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