Thanks for asking me to respond. If you have chronic ACL tear, then the knee becomes unstable especially when running or jumping, or going up stairs. However with a good physio program, you can strengthen the quads and Hamstring muscles of your thigh. They can help stabilize the knee while playing or running. Try physio for 3 months. If you still continue to have instability then you have to strongly consider undergoing key hole surgery to reconstruct the ligament. This will restore stability in the knee. There are no medicines to make the ligament heal. Good luck.