Early Open Kinetic Chain Hamstring Exercise After ACL Reconstruction: A Retrospective Safety and Efficacy Study

A new study from Journal of Clinical Medicine (2025) challenges one of rehab’s long-standing taboos: the idea that open-kinetic-chain (OKC) hamstring work should be delayed for 6–8 weeks after ACL reconstruction.

What they did:
Thirteen young adults (18–35 yrs) who had ACL reconstruction with a hamstring graft began targeted hamstring exercises — seated leg-curls and long-lever glute bridges — just three weeks post-op, twice per week, under close supervision.

What they found:
✅ No complications or graft issues.
✅ Pain stayed low (≈2.5/10) across all 234 rehab sessions.
✅ Hamstring strength improved significantly from week 6 → 12, especially at deeper knee flexion angles.
✅ Limb symmetry index at 90° increased from 65 % to 83 %.

What it means:
Early OKC hamstring loading appears safe and beneficial in this small pilot sample. It may help counter the common strength deficits seen after hamstring-graft ACLR — though the authors emphasize that larger, controlled trials are still needed before changing guidelines.

Take-home:
💡 Starting gentle, controlled hamstring work at week 3 could speed strength recovery — provided pain and swelling are minimal and progressions are well-monitored.