Material and Methods: Patients with ACL re-injury to either knee after successful primary ACLR were included in Group I and those with no further re-injury were included in Group II. Variables including age, gender, side, body mass index (BMI), thigh atrophy, anterior knee laxity difference between both knees measured by KT-1000 arthrometer, mean time of return to sports (RTS), graft type, type of game, mode of injury, Tegner Activity Score, hormone levels, femoral tunnel length (FTL), posterior tibial slope (PTS) and notch width index (NWI) were studied. Binary logistic regression was used to measure the relative association.

Results: A total of 128 athletes were included with 64 in each group. Mean age in Group I and II were 24.90 and 26.47 years respectively. Mean follow-up of Group I and Group II were 24.5 and 20.11 months respectively. Significant correlation was present between ACL re-injury and following risk factors; PTS of >10º, KT difference of >3.0mm, thigh atrophy of >2.50cm and time to RTS <9.50 months P value <0.05). No correlation was found with age, sex, BMI, type of game, Tegner Activity Score, mode of injury, NWI, size of graft, FTL and hormone levels.

PURPOSE: (1) To present the evidence of platelet-rich plasma injection in the treatment of hamstring injuries, (2) evaluate the "best-case scenario" in dichotomous outcomes, and (3) evaluate the "worst-case scenario" in dichotomous outcomes.

STUDY DESIGN: Systematic review and meta-analysis.

METHODS: Two authors systematically reviewed the PubMed, Embase, and Cochrane Library databases according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, with any discrepancies resolved by mutual consensus. The level of evidence was assessed per the criteria of the Oxford Centre for Evidence-Based Medicine and the quality of evidence by the Coleman Methodology Score. Meta-analysis by fixed effects models was used if heterogeneity was low (I2 < 25%) and random effects models if heterogeneity was moderate to high (I2≥ 25%). P values return to play that compared platelet-rich plasma + physical therapy to physical therapy alone non-significantly favored platelet-rich plasma + physical therapy (mean difference, -5.67 days). The fixed effects model for reinjury rates, which also compared platelet-rich plasma + physical therapy with physical therapy alone nonsignificantly favored platelet-rich plasma + physical therapy (risk ratio, 0.88). The best-case scenario fixed effects model for reinjury rates nonsignificantly favored platelet-rich plasma + physical therapy (risk ratio, 0.82). The worst-case scenario fixed effects model for reinjury rates nonsignificantly favored physical therapy alone (risk ratio, 1.13). The mean ± SD complication rate for either postinjection discomfort, pain, or sciatic nerve irritation was 5.2% ± 2.9% (range, 2.7% to 9.1%).