Background and Etiology
Ligaments are fibrous bands of connective tissue, made of collagen, that join bone to bone. Ligaments provide the joint with stability and limit excessive motion. The knee has four major ligaments: the medial collateral (MCL), lateral collateral (LCL), anterior cruciate (ACL) and posterior cruciate (PCL) ligaments. Each of these ligaments performs a specific role in creating stability in the knee, the largest joint in the body. If a ligament is injured or torn, both the function and stability of the knee can be compromised.
Anterior Cruciate Ligament
The Anterior Cruciate Ligament is an important ligament stabilizer in the knee. It is located within the knee joint and is attached to the back of the femur (thigh bone,) and runs to the front of the tibia (lower leg.) This ligament prevents the tibia from sliding forward on the femur and also limits rotational movement of the knee joint.
Anterior Cruciate Ligament Tear
An injury to the anterior cruciate ligament can range from a partial to a complete tear. When the ACL is torn the stability of the knee can be compromised. The loss of the ACL will result in excessive anterior (sliding forward) and rotatory (twisting) movement of the tibia on the femur. This can produce increased wear and tear on the meniscus and cartilage of the knee joint. ACL tears are more common in women than in men. Adults typically tear the ACL mid-ligament while children may tear-off a piece of the leg bone where the ligament attaches.
Anterior Cruciate Insufficiency
When the ACL is partially or completely torn the stability of the knee can be compromised; this may be referred to as ACL Insufficiency. ACL Insufficiency can also cause excessive anterior (sliding forward) and rotatory (twisting) movement of the tibia on the femur. This can result in increased wear and tear on the meniscus and cartilage of the knee joint. Individuals with ACL Insufficiency may be more likely to experience meniscus and cartilage damage, especially due to participation in sports.
The ACL can be injured when:
- The knee experiences a hyper-extended (bent backward), side-to-side or twisting motion particularly when the foot is in contact with the ground.
- The knee experiences a sudden blow or contact by another person
- A sudden cutting, stopping or twisting motion occurs or landing from a jump when playing sports like soccer, basketball, football or skiing.
- Pain and swelling of the knee following injury that may be caused by bleeding following the ligament tear.
- A “pop” in the knee may be heard or felt at the time of the injury.
- Difficulty walking due to a feeling of instability or “giving out” of the knee.
- Loss of motion when trying to bend and straighten the knee.
In response to this type of injury one should initiate the RICE protocol of Rest, Ice, Compression and Elevation in addition to the following:
- Rest by stopping activity immediately to avoid aggravating the injured knee and ligament.
- Immobilization to keep the ligament from being further stressed.
- Ice, compression and elevation to reduce inflammation and pain for the first 48-72 hours. Do not apply ice directly over the skin and only use ice intermittently during the day. Apply the ice for 20 minutes at a time. Do not apply any form of heat during this period.
- Contact your physician or medical provider for complete diagnostic evaluation of the injury and follow up care.
Your physician will perform a series of clinical tests as part of an evaluation to determine the severity of the knee injury and the appropriate course of treatment. These tests will include an X-ray, general examination and assessment of knee stability. In addition, an MRI may be indicated if the injury is severe.
Following an injury to the ACL one should seek a full evaluation from a physician or health care provider. Treatment may consist of the following:
- Clinical evaluation including a physical exam, X-rays and MRI in more severe Grade III and Grade IV injuries
- Use of ice and immobilization to stabilize and rest the joint
- Anti-inflammatory medication and pain medication (as needed)
- Progression to a brace or immobilizing device to stabilize or rest the joint.
- Physical Therapy
- Surgery may be indicated for complete ACL tears, especially if other structures of the knee are involved in the injury.
The medical treatment of an ACL tear will depend on a number of variables, which may include:
- Severity of the injury, which can be a partial or a complete tear of the ligament
- Possibility that other structures are affected, like the medial meniscus or the medial collateral ligament.
- The patient’s activity level, lifestyle, occupation or amount of instability as effected by the injury. Clinical testing during the examination will be performed to determine instability.
- Age is a factor in the decision to have a surgical reconstruction. Older people who are sedentary are less likely to have a surgical procedure than younger individuals who are very active.
Following a complete examination of the knee a physician may recommend a course of physical therapy for the following reasons:
- Taking into account the individual’s age, activity level, lifestyle, occupation or amount of instability, physical therapy may be the best treatment option. This is especially true for a partial ACL tear.
- If there is a great deal of swelling, pain or loss of motion it is recommended that the individual undergo physical therapy to improve the condition of the knee in preparation for surgery or to determine if surgery is necessary. As a general rule the better the condition of the knee prior to surgery, the better the surgical outcome.
- If following an extensive course of therapy, the level of stability and function is not satisfactory surgery may be indicated.
Physical Therapists are professionals, educated and trained to administer interventions. As stated in The Guide to Physical Therapist Practice interventions are the skilled and purposeful use of physical therapy methods and techniques to produce changes consistent with the diagnosis, prognosis and the goals of the patient or client.
Initial treatment will focus on protecting the ligament if it is partially torn, reducing pain and swelling and restoring motion. As the physical therapy program progresses strengthening, flexibility and aerobic exercises in addition to technique and proprioceptive training to protect the knee and ligament will be added to help restore a normal level of activity.
Following surgery, some patients will present with stiffness, loss of motion and weakness due to muscle atrophy. These patients will require intensive physical therapy, following post surgical protocols as determined by the surgeon. These protocols are designed to protect the ligament to promote healing, while reducing pain and swelling. Emphasis is placed on the restoration of motion, strength and function on a weekly basis. Post surgical rehabilitation is critical to a good outcome and may take up to six months. Patients can expect to see improvement and gains in function for up to a year.
Common physical therapy interventions for this condition include:
- Manual Therapeutic Technique (MTT): hands on care including soft tissue massage, deep friction massage and joint mobilization by a physical therapist to regain mobility and range of motion of the knee.
- Therapeutic Exercises (TE) including stretching and strengthening exercises to regain range of motion and strength to protect and stabilize the knee and the affected ligament.
- Neuromuscular Reeducation (NMR) to restore stability, begin retraining the lower extremity chain and improve movement techniques and mechanics (running, jumping and cutting) that use the involved knee in daily activities.
- Modalities that can include the use of ultrasound, electrical stimulation, ultrasound, ice, cold laser and others to decrease pain and inflammation at the knee and ligament.
- Home program that includes strengthening, stretching and stabilization exercises and instructions to help the performance of daily tasks and advance to the next functional level.
Due to poor circulation, the ACL will not heal on its own and surgical intervention is typically required. Surgical intervention is usually performed several weeks after the injury to allow for the reduction of pain, swelling and improvement in motion. The ligament cannot be repaired but it is reconstructed using other tendons or ligaments in the body. Some common reconstruction options are:
- Patella Tendon: In this procedure a central portion of the patella tendon attached to a piece of bone from the kneecap on one end and from the tibia on the other end (BTB) is used to reconstruct the ACL. This is a very common approach and typically results in good outcomes. The disadvantage to this procedure is that it can be include a painful rehabilitation process, and it may weaken the patella tendon.
- Hamstring Tendon: In this procedure a portion of one of the patient’s hamstring tendons is taken and the ACL ligament is reconstructed. This is also a common technique that typically results in good outcomes. The advantage to this procedure is that it is often less painful than the patella tendon approach. The disadvantage is that it may take longer to heal as there is no bone involved.
- Cadaver Ligament: In this approach an ACL is harvested from a cadaver and is used to reconstruct the injured knee. The advantage of this technique is that there is less postoperative pain because there is no ligament harvesting from the patient. The disadvantage of this procedure is that there is a slightly higher chance of infection.
The prognosis for these injuries is good when they are cared for correctly. The rehabilitation program will depend on what procedure(s) are performed and the surgeon’s postoperative protocol. On average rehabilitation following ACL reconstruction will take 7-9 months. Individuals may continue to see improvement for up to a year following surgery. The rehabilitation process is a step-by-step process. The final stages should involve high-level functional training to prepare for a return to activity and sport. Your surgeon may recommend bracing for athletic activities to help stabilize the knee during sports.