ACL Tear anterior cruciate ligament tear ACL sprain
The ACL is a ligament in the knee that helps to stabilize the knee joint.  It is one of the ligaments that attach the femur (thigh bone) to the tibia (shin bone).  A knee injury can stretch and tear the ACL.
ACL tears are usually caused by one of three types of injuries:  rapid deceleration (trying to suddenly stop or change direction while sprinting), hyperextension, or quickly pivoting on a leg that is firmly planted on the ground.
A torn ACL can cause chronic pain and can prevent athletes from performing well because the knee becomes unstable.  Instability from a torn ACL may also result in mechanical changes in the knee joint that wear away at the cartilage and lead to an earlier onset of arthritis.
ACL tears are diagnosed based on a history, physical exam, and MRI.  Patients usually have a history of a sports injury or fall and often report hearing or feeling a pop.  The knee quickly swells up after the injury.  Athletes are typically unable to continue to compete immediately following the injury.  The knee may feel wobbly and unstable.
Physical exam findings change depending on how soon after the injury the knee is examined.  Soon after the injury, the knee may be too swollen and painful to effectively examine.  If fluid is drained from the knee it is bloody.  The integrity of the ACL is tested with the anterior drawer test and Lachman’s test.
ACL tears are not visible on x-rays, but they are often obtained to look for evidence of fractures or arthritis.  Occasionally, an injury to the ACL will pull a small piece of bone from the tibia, which can be identified on x-rays.  If an ACL tear is suspected, an MRI is obtained.  ACL tears are usually identified on the MRI.
Older, less active people may do well with non-surgical treatment.  People with partial tears in which part of the ACL is still intact may also respond well to non-surgical treatment.  Treatment options include anti-inflammatory medications such as ibuprofen, steroid injections, ice, elevation, activity modification, physical therapy, and bracing.
People with complete ACL tears, especially young, active people, will do better with surgery.  The ACL will not heal and must be reconstructed.  Surgery is usually done arthroscopically (through a knee scope).  A graft is passed through tunnels in the tibia and femur and fixed in place.  Recovery after ACL reconstruction requires months of rehabilitation, but most athletes are able to return to playing their sport 6 months to 1 year after surgery.
ACL Tears
MRI normal ACL
ACL tear
ACL Reconstruction Surgery
ACL Tears Diagnosis