The ACL is one of the four major ligaments in the knee. It connects the femur (thigh bone) to the tibia (shin bone) and provides stability to the knee. The ACL can be torn from contact or non-contact injuries. Common causes of the injury include landing awkwardly from a jump, changing direction rapidly, or from direct contact/collision. Partial ACL tears can happen, but complete tears are much more common.

When the ACL tears, people describe hearing or feeling a “pop” in their knee. The knee also frequently gives out and swells. An ACL tear can continue to result in instability of the knee. Some people experience this instability during daily activities like walking around the house while others only experience it when twisting or pivoting. It is common to also damage the meniscus or cartilage in the knee during an ACL injury. Damage to either of these structures can cause increased pain.


Unfortunately, ACL tears do not heal on their own, but not everyone requires surgery. Those who are less active or do not experience knee instability on a daily basis can do well without surgery. Sometimes people who injure their ACL will give up activities like sports to avoid surgery. Non-operative treatment initially focuses on reducing swelling and restoring normal knee range of motion. The goal of non-operative treatment is to strengthen the muscles that support the knee to minimize the frequency of the knee feeling unstable.

Those who place higher demand on their knee, like athletes or those in labor-intensive occupations, will usually require surgery to reconstruct the ACL. During surgery, a new ACL is created because the old ACL cannot heal, even when sutured back into place. A graft is used to create a new ACL and restore stability to the knee. Range of motion exercises begin immediately after surgery. Long-term outcomes for ACL surgery are best for those who restore full range of motion. It is important to avoid twisting or pivoting exercises as these can put the ACL graft at risk. It takes approximately six months to return to full activities, but you shouldn’t experience pain in your knee the entire time.

For a large majority of patients, the outcomes from ACL surgery are excellent. However, as with any surgery, complications are possible. The most common complications are numbness around the incision, residual knee stiffness and on-going pain. There is also a risk of re-tearing the ACL graft, but the likelihood of this happening is approximately the same as tearing your native ACL.