Anterior Cruciate Ligament tear

ACL anatomy

The ACL consists of individual fiber bundles, named from their insertion points on the tibial footprint. The larger anteromedial (AM) bundle inserts anteromedially on the tibial side and originates more proximally on the femoral side than the posterolateral (PL) bundle, which is posterolateral relative to AM bundle.

Studies indicate that the AM bundle tightens in flexion while the PL bundle relaxes; in extension, the PL bundle tightens while the AM bundle relaxes. What is unusual about the workings of the two bundles is the way their insertion points on the femur relate to each other in flexion and extension. In extension, their insertion points are vertical to each other, but with the knee in 90 degrees flexion, the insertion points are horizontal to each other. Likewise, the bundles themselves shift from parallel orientation in extension to crossed orientation in flexion.


The ACL bandles: ΑΜ (ΑnteroΜedial), PL (Postero-Lateral)

What causes a torn ACL?
Most anterior cruciate ligament injuries occur due to trauma, usually in sport 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.

Pivot Torn ACL  

Μost common in men or women?
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.

Q angle

What are symptoms and signs of a torn ACL?
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, swelling and giving way, especially when walking on uneven ground or climbing up or down steps.

Severe knee effusion

How is a torn ACL diagnosed?
The diagnosis of an ACL injury begins with the care provider taking a history of how the injury occurred. Often the patient can describe in detail their body and leg position and the sequence of events just before, during, and after the injury as well as the angle of any impact.Physical examination of the knee usually follows a relatively standard pattern.The knee is examined for obvious swelling, bruising, and deformity. Areas of tenderness and subtle evidence of knee joint fluid (effusion) are noted. Most importantly, with knee injury ligamentous, stability is assessed. Since there are four ligaments at risk for injury, the examiner may try to test each to determine which one(s) is (are) potentially damaged. In the acute situation, with a painful, swollen joint, the initial examination may be difficult because both the pain and the fluid limit the patient's ability to cooperate and relax the leg. A variety of maneuvers can be used to test the stability and strength of the ACL. These include the Lachman test, the pivot-shift test, and the anterior drawer test. The unaffected knee may be examined to be used as comparison. It may be difficult to examine some patients when muscle strength or spasm can hide an injured ACL because of the knee stabilization that they can provide.

Plain X-rays of the knee may be done looking for broken bones. Other injuries that may mimic a torn ACL include breakage in the end of the thighbone (such as a tibial plateau fracture or a tibial spine fracture). In patients with an ACL tear, the X-rays are usually normal. Magnetic resonance imaging or ΜRI has become the test of choice to image the knee looking for ligament injury. In addition to defining the injury, it can help the orthopedic surgeon help decide the best treatment options.

Noulis test

ACL tear

What is the treatment for a torn ACL?
The major decision in treating a torn ACL is whether the patient would benefit from surgery to repair the injury. The surgeon and the patient need to discuss the level of activity that was present before the injury, what the patient expects to do after the injury has healed, the general health of the patient, and whether the patient is willing to undertake the significant physical therapy and rehabilitation required after an operation.

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. Physical therapy 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 necessary. Return of range of motion is also a key component of therapy.

How long does it take to recover from a torn ACL?
Rehabilitation and return to normal function after surgical repair of an ACL tear can take nine months or more. There needs to be a balance between trying to do too much work in physical therapy returning strength and range of motion and doing too little. Being too aggressive can damage the surgical repair and cause the ligament to fail again. Too little work lengthens the time to return to normal activities.More than 80% of people who have surgery to repair their ACL have good return of function and lifestyle. Less than 10% of patients develop permanent knee instability

Knee brace