The ACL, or anterior cruciate ligament, is one of the key structures in your knee joint and one of its functions is to resist forward motion of your tibia, the bone in your lower leg. When it gets injured, there is nothing to prevent your tibia from moving forward and the knee joint becomes unstable. Orthopedic surgeons are able to reconstruct the ACL using grafts from muscles or tendons elsewhere in your body, bio-bridges or cadaver implants allowing for athletes to return from what used to be a career ending injury.
The healing time required for the new ACL is the reason for such a long rehabilitation. It is important for the graft to have time to remodel in order to be strong enough to withstand sport specific tasks. Around 3 months post-op, most patients find that their knee is doing well and they have very little limitations in motion, swelling and walking. However, believe it or not, this is the most crucial time in ACL recovery, as the new ACL is at its weakest and has a high risk of re-tearing if returning to sport too soon. 32 weeks postop is now the most common time period to return to your sport and the majority of evidence would indicate that returning sooner would lead to a higher rate of re-injury.
Physical therapy is crucial in your rehabilitation following an ACL reconstruction in order to not only regain range of motion, decrease swelling and pain and work on strengthening your muscles, but to re-teach your body and brain how to perform sport specific activities such as running, jumping, and cutting. Returning too early can greatly increase your risk of re-injury and start this process all over again. Why risk it?