[physiobob]

Yep that's exactly what it sounded like. The fixation to the femur. It is unlikely that the repair 'snapped' however it is possible that the tendon replacement has come unstuck from the fixation screw. This is hard to diagnose clincially when you have acute swelling and an injured hamstring as it is difficult to perform a Lachman's text (ACL test) without overactive hamstrings mimicking a good stable fixation. Also tests like pivot shift with any real pressure would be avoided in the early phases following the surgery as one would not want to compromise the graft while it is healing.

Tough one right now to say anymore without seeing the knee first hand. Maybe a followup MRI would show if the graft is in place correctly.