A torn ACL, or anterior cruciate ligament, occurs commonly in athletes who participate in high demand sports such as football, basketball and soccer. It can occur several different ways. Changing direction quickly, stopping suddenly, landing from a jump incorrectly, or a direct collision are a few examples. Studies have shown that female ACL injuries are more common among females than males. It’s possible that this occurs because of the difference is muscle strength or the difference in pelvis alignment. The anterior cruciate ligament runs diagonally in the middle of the knee. It is found inside the knee joint and crosses in front of the posterior cruciate to form an “X”. It functions to prevent the tibia from sliding out in front of the femur. It also provides rotational stability to the knee.Injured ligaments are graded on a severity scale. First, there are grade 1 sprains. This is a mild injury where the ligament has been slightly stretched by is still able to function. Grade 2 sprains occur when the ligament stretches to the point of becoming loose, also known as a partial tear. Grade 3 sprains is known as a complete tear of the ligament where it has been split into two pieces and the knee joint is unstable. When this injury occurs, a “popping” noise often follows and the knee may give out. If there is no pop, many can feel the shifting of the joint. Swelling of the joint occurs almost immediately and is usually large. The swelling that occurs is usually hemarthrosis, or filled with blood. Other symptoms loss of full range of motion, tenderness along the joint line, and discomfort while walking. The injury may require surgery depending on its severity. If the ACL is torn, it will not heal without surgery. However, for patients who have a very low activity level and an overall stable knee, there are nonsurgical options. The first option is a brace to protect the knee from instability along with crutches to keep the weight off. Physical therapy may help restore knee function and strength the muscles that support it. If surgery is required, most ACL tears cannot be sutured back together. The ligament must be reconstructed with a tissue graft that helps support new ligament growth. The grafts can be taken from the patellar tendon, hamstring tendon, or a quadriceps tendon. The surgery itself is done with an arthroscope using small incisions. The regrowth of the tendon takes time so it may be six or more months before an athlete is able to return to sports. Physical therapy helps to regain knee strength and motion. The first step in physical therapy is return the motion to the joint and surrounding muscles. Next is a strengthening program to help protect the new ligament. Over time, the program gradually increases the stress across the ligament. The final step is working on a return tailored to the athlete’s sport.