Modifiable factors and their association with self-reported knee function and activity after anterior cruciate ligament reconstruction: a systematic review and meta-analysis

Objective: To determine if body mass index (BMI), smoking status, prehabilitation or time to reconstruction are associated with recovery of self-reported knee function and activity after ACL reconstruction (ACLR). Data Sources: Four electronic databases were systematically searched. Study Selection: English language articles were included if: (1) participants aged 16-70 years had primary or first revision ACLR with autograft, following complete rupture; and (2) the association between one of four modifiable factors: (1) BMI; (2) smoking; (3) prehabilitation; or (4) time to reconstruction with self-reported knee function and activity, ACL graft rupture or return to sport was evaluated. Results: Twelve articles (representing 11 studies) were included. Meta-analyses found low-quality evidence of no difference in self-reported knee function (d = -0.07, 95% CI -0.37 to 0.23, I-2 = 0%) or activity levels (d = 0.11, 95% CI -0.2 to 0.41, I-2 = 0%) between acute and subacute ACLR. There was no difference in the relative risk of ACL graft rupture with the timing of ACLR (one study). Meta-analysis demonstrated very low-quality evidence that smokers had worse self-reported functional outcomes after ACLR compared to non-smokers (d = -0.58, 95% CI -0.788 to -0.28, I-2 = 59%). One study suggested an inverse relationship between BMI and knee-related quality of life after ACLR. One RCT suggested prehabilitation may reduce time to return to sport. Conclusion: Low-quality evidence suggests there is no difference in delaying ACLR and very low-quality evidence suggests smokers have worse self-reported functional outcome after ACLR compared to non-smokers. High-quality RCTs are needed to confirm the relationship between the four modifiable factors studied and ACLR outcome.