OBJECTIVES: To assess the implementation, limited efficacy, and acceptability of the BEAST (better and safer return to sport) tool - a rehabilitation and return-to-sport (RTS) decision tool after anterior cruciate ligament reconstruction (ACLR) in nonprofessional athletes.

DESIGN: Prospective cohort.

PARTICIPANTS: 43 nonprofessional pivoting sport athletes with ACLR.

MAIN OUTCOME: Clinician- and athlete-experienced implementation challenges (implementation), changes in quadriceps power, side hop and triple hop performance from 6 to 8 months after ACLR (limited efficacy), athletes' beliefs about the individual rehabilitation and RTS plans produced by the BEAST tool (acceptability).

RESULTS: The BEAST tool was developed and then implemented as planned for 39/43 (91%) athletes. Hop and quadriceps power performance improved significantly, with the largest improvement in involved quadriceps power (standardised response mean 1.4, 95% CI:1.1-1.8). Athletes believed the rehabilitation and RTS plan would facilitate RTS (8.2 [SD: 2.0]) and reduce injury risk (8.3 [SD: 1.2]; 0 = not likely at all, 10 = extremely likely).

CONCLUSION: The BEAST tool was implemented with few challenges and adjustments were rarely necessary. Athletes had large improvements in quadriceps power and hop performance on the involved leg. Athletes believed that the individual rehabilitation and RTS plans produced by the tool would facilitate RTS and reduce injury risk.