The anterior cruciate ligament (ACL) has no healing potential. If it is torn it will therefore remain deficient. This does not mean that everyone with an ACL tear will need a reconstruction operation. A small percentage of people with a torn ACL do not have episodes of the knee giving way (instability). We refer to this group as “copers” (meaning they can cope without an ACL or have a partially torn ACL). This may be due to factors such as the individual’s biomechanics, muscle strength or proprioception. If you are involved in a so-called pivot sport (this includes all ball sports) the ACL is important to stabilize your knee when you change direction suddenly. If your ACL is torn you will therefore need an ACL reconstruction operation should you wish to continue to take part in pivot sports. In general this instability does not occur in so-called straight line sports such as jogging and cycling. However the knee may be so unstable that it gives way even with normal daily activities. In such cases an ACL reconstruction is also necessary.
Keep in mind that when the knee gives way as result of a torn ACL the tibia rotates relative to the femur. This causes the knee to pop in and out of joint in quick succession and in so doing huge stresses are placed on the medial and lateral meniscus as well as the joint surface. At the time of the initial injury there is also a high incidence of associated injuries such as meniscus tears, joint surface damage and other ligament injuries. If you have an associated injury this will almost certainly mean that surgery is essential. Any athlete can also not confidently take part in pivot type sport with the risk of the knee giving way.
A successful ACL reconstruction will prevent recurrent giving way and subsequent further damage to the knee joint. Unfortunately no matter how hard we try to accurately reconstruct the ACL we cannot recreate the normal anatomy perfectly. We therefore cannot guarantee that an ACL reconstruction operation will definitely prevent later onset of osteoarthritis of the knee. There is however no doubt that the recurrent giving way of your knee when the ACL is torn will increase your risk for developing osteoarthritis of the knee later in life.