ACL Tear Overview

Healthy Knee Arthritic Knee
Healthy Knee ACL Tear

The ACL (Anterior Cruciate Ligament) is one of the four main ligaments in the knee. The ligament connects the thighbone (femur) to the shinbone (tibia), keeping the knee from hyperextending, which prevents forward (anterior) dislocation at the tibia. The ACL also provides rotational stability and support to help prevent unnatural movement in the joint. If the knee is twisted, bent side to side, or hyperextended, the ACL can be injured.

An ACL tear often occurs during high-impact sporting events or when the knee experiences a large amount of turning and twisting. A torn ACL usually occurs when a force is applied to the knee while the foot is firmly planted on the ground or upon landing.

Contact sports or high-impact actions involving rapid twisting movements place extreme force on the knee, which can lead to injury. Basketball, football, soccer, baseball, tennis and skiing are common activities that can lead to a tear or rupture of an ACL. Older adults can also suffer from ACL injuries as the ACL becomes weaker with age. Simple activities such as missing a step on a staircase, stepping in a hole, or falling can cause ACL tears.

When the ACL tears, people often describe hearing a pop and feeling the knee "give out" or buckle. A torn ACL often results in swelling and a loss of stability in the knee, sometimes referred to as "feeling loose."

A torn ACL can be painful and swelling of the knee will usually begin immediately after injury or within 24 hours. A loud popping or cracking sound can be heard at the time of the injury and there may be some pain at the time of the impact, which over time may be felt in the calf region. The patient may feel some instability of the joint, perhaps creating the feeling of the knee "giving way."

There are several different types of ACL tears: a partial tear of the ligament, a complete tear of the ligament (rupture), and rarely-the very end of the ligament remains attached to a small piece of bone which breaks or separates from the lower leg bone (avulsion). Many patients who sustain an ACL tear may opt to have surgical reconstruction of the ligament, which is most commonly performed arthroscopically. Arthroscopic surgery allows short incisions by using an arthroscope, a small tube-like instrument that allows the surgeon to see inside the joint.

Biomet is a manufacturer of orthopedic implants and does not practice medicine.

This information was prepared in conjunction with a licensed physician and is presented as general information only. Only an orthopedic surgeon can determine what treatment is appropriate. The life of any implant will depend on your weight, age, activity level, and other factors. For more information on risks, warnings, and possible adverse effects, see the Patient Risk Information section found within Always ask your doctor if you have any questions regarding your particular condition or treatment options.