Sports injuries

The anterior cruciate ligament is one of several incredibly integral parts of a fully functioning knee, keeping the bones of the upper and lower leg in their proper places, preventing hyperextension, and limiting internal rotation in the knee joint. But, as so many people involved in sports or sports medicine know, it’s also one of the ligaments most often damaged in sports injuries involving the knees. These injuries are generally classified as sprains, with grade I sprains being the least severe and grade III sprains being the most severe. Here’s what you should know about each grade of ACL sprain:

Grade I

A grade I ACL sprain involves overstretching but no tearing of the ligament’s fibers. You may experience a small amount of tenderness and swelling, but your knee should not feel unstable or give out while you are using it.


Rest and measures to prevent swelling (such as icing and taking nonsteroidal anti-inflammatory drugs) are often sufficient. It is wise to seek out physical therapy in order to build up strength in the knee again and prevent re-injury.

Grade II

A grade II sprain involves partial tears in the fibers of the ligament. You will likely experience tenderness and swelling, and the knee may feel unstable or give out.


Treatment is similar to that for a grade I sprain, although generally more prolonged. It is important to strengthen and stretch the knee and associated muscle systems in the leg as part of physical therapy. A doctor may recommend wearing a knee brace for a set length of time. With diligent work, the knee may fully recover in two to eight weeks.

Grade III

A grade III sprain is a rupture, meaning the ligament is completely torn. The ligament may tear itself into two parts, or your ACL may tear away from either the femur or tibia. The latter is called an ACL avulsion (or an avulsion fracture, if a piece of bone is torn away with it). You may experience quite a lot of swelling, but not all people do; furthermore, you may experience tenderness but surprisingly little pain. You will not be able to control your knee joint’s movement, and the knee will feel unstable.


ACL surgery is necessary to treat a grade III sprain. There’s actually more than one kind of ACL surgery; ACL reconstruction involves a graft that replaces the ligament, and ACL repair involves reattaching the bone in the case of an avulsion fracture. Most ACL surgery is done arthroscopically, meaning tools are inserted through tiny slits in the knee. This can allow for a much shorter recovery time than open knee surgery.

Questions? Comments? Join the discussion below.