Q: How is it possible to strengthen muscles to take the place of a torn ligament? I went through a three month rehab program for a torn MCL that worked like a charm. But I still don't get how a muscle can do the job of a ligament.

A: That's a good question and one that we have more answers for now that advanced imaging technology has helped us understand the basic anatomy of ligaments and other soft tissues.

People with an isolated medial collateral ligament (MCL) injury have the best chance of recovery without surgery. But most MCL injuries are part of a more complex (combined) injury that includes other soft tissues. It's those combination injuries that are more likely to leave the patient with an unstable joint that requires surgery.

Let's back track a little and see how the anatomy and biomechanics of the medial collateral ligament affect treatment choices and recovery. The name medial tells us the ligament is on the side of the knee closest to the other knee.

This ligament has both parallel and diagonal fibers that run between the tibia (lower leg bone) and the femur (upper leg bone). The dual directional fibers are necessary to provide stability and restraint to the knee joint.

The anatomy is fairly complex as the fibers are interwoven in superficial and deep layers with the fascia (connective tissue). In the same way, the MCL interconnects with other nearby soft tissue structures along the medial side of the knee. In addition, the hamstring muscle, which wraps around the knee from the back of the thigh adds dynamic support to the medical collateral ligament (MCL).

One key feature of the medial collateral ligament (MCL) that directs treatment is the fact that it is one of the few ligaments that can heal itself. It is located outside of the joint so with the right kind of management, many MCL injuries can be remodeled and restored enough to support load placed on the knee.

A second important factor is the relationship of the MCL to its supporting structures. Dynamic reinforcing fibers from the hamstring muscle makes it possible for the knee to cope with higher stress and load across the knee. By strengthening this muscle group and maintaining a good balance of muscle support, the joint is supported without the MCL ligament.

If, after a good three-to-six months' of rehab, the knee is still unstable, then surgery is a second option. But the rehab program (really a "prehab" program in such cases) isn't wasted time. Many surgeons recommend this type of training before surgery to help ensure the best possible outcomes after surgery.

Reference: Milford H. Marchant, Jr., et al. Management of Medial-Sided Knee Injuries, Part 1. Medial Collateral Ligament. In The American Journal of Sports Medicine. May 2011. Vol. 39. No. 5. Pp. 1102-1113.