The ACL arises from the front of the medial femoral condyle and passes through the middle of the knee to attaches between the bony outcroppings (called the tibia spine) that are located between the tibia plateaus. It is a small structure, less than 1 ½ inches long and ½ inch wide. But regardless of its size, the anterior cruciate ligament is vital in preventing the thighbone (femur) from sliding backward on the tibia (or, from the other point of view, the tibia sliding forward under the femur). The ACL also stabilizes the knee from rotating, the motion that occurs when the foot is planted and the leg pivots.

Without a normal ACL, the knee becomes unstable and can buckle, especially when the leg is planted and attempts are made to stop or turn quickly.

Causes a torn ACL:

Most anterior cruciate ligament injuries occur due to trauma, usually in a sport or fitness activity. The ligament gets stretched or tears when the foot is firmly planted, the knee locks and twists or pivots at the same time. This commonly occurs in basketball, football, soccer, and gymnastics, where a sudden change in direction stresses and damages the ligament. These injuries are usually noncontact, occur at low speed, and occur as the body is decelerating

ACL injuries may also occur when the tibia is pushed forward in relation to the femur. This is the mechanism of injury that occurs because of a fall when skiing, from a direct blow to the front of the knee (such as in football), or in a car accident.

Women are more prone to ACL injuries than men. Women have slightly different anatomy that may put them at higher risk for ACL injuries:

• The intercondylar notch at the end of the femur is narrower in women than men. When the knee moves, this narrower space can pinch and weaken the ACL.

• Women have a wider pelvis than men and this causes the femur to meet the tibia at a greater angle (called the Q angle). This increases the force applied to the ACL with any twisting motion, increasing the risk of damage.

• Women may have a greater imbalance in the strength of the quadriceps muscle in relation to the hamstrings. This increases the stress on the ACL to stabilize the knee and potentially causes it to fail.

 Symptoms and Signs:

With an acute injury, the patient often describes that they heard a loud pop and then developed intense pain in the knee. The pain makes walking or weight-bearing very difficult. The knee joint will begin to swell within a few hours, making it that much harder to try to straighten the knee and walk.

If left untreated, the knee will feel unstable and the patient may complain of recurrent pain and swelling and giving way, especially when walking on uneven ground or climbing up or down steps.

Treatment:

Nonsurgical treatment may be appropriate for patients who are less active, do not participate in activities that require running, jumping or pivoting, and who would be interested in physical therapy to return range of motion and strength to match the uninjured leg.

The anterior cruciate ligament can be reconstructed using arthroscopic surgery. There are a variety of techniques, depending on the type of tear and what other injuries may be associated.

Physical therapy (Physiotherapy) is the mainstay of rehabilitation and therapy regardless of whether or not an operation is performed. The quadriceps and hamstring muscles "shut down" and weaken with any knee injury and strengthening exercises are needed. Return of range of motion is also a key component of therapy.