Quadriceps femoris strength deficits early in rehabilitation after ACL reconstruction identify risk of future contralateral ACL injury following return to sport in young athletes: A Preliminary analysis.

OBJECTIVE

To test the relationship between quadriceps femoris (QF) strength 3 months after ACLR and long-term outcomes after ACLR.

DESIGN

Prospective, case-cohort.

SETTING

Laboratory.

PARTICIPANTS

51 (mean age:15.6 ± 2.2 yrs) athletes after ACLR.

MAIN OUTCOME MEASURES: 1) "Early" (13.7 ± 2.1 wks) post-ACLR testing included an isokinetic QF strength assessment. 2) At medical clearance to RTS (8.4 ± 1.6 months), isokinetic QF strength, hop testing, and patient-reported outcome data were collected. Associations between early QF strength and RTS measures, as well as 2nd ACL injury in the 36 months after RTS were assessed.

RESULTS

20 participants (39 %) sustained a 2nd ACL injury after RTS. Early QF strength limb symmetry (LSI) was moderately correlated with measures at RTS clearance (p < 0.05). Participants who failed to achieve ≥80 % QF LSI at the early testing session (23/51; 45.1 %) had 4 times higher odds (OR = 4.4; 95 %CI:1.0-19.2; p = 0.04) of sustaining a contralateral 2nd ACL injury in the 36 months following RTS clearance.

CONCLUSION

Early QF LSI positively associates with RTS measures. Early QF strength symmetry <80 % was associated with increased risk of contralateral ACL injury after RTS. Greater QF strength deficits early in rehabilitation may be a biomarker of poor short- and long-term outcomes after ACLR.