Anterior Cruciate Ligament Injury - Signs, Symptoms, Diagnosis and Treatment

Introduction

The anterior cruciate ligament (ACL) is a thick band of connective tissue that secures the femur (thigh bone) to the tibia (shin bone). It is an essential structure in the knee joint located in the middle of the knee, preventing the shin bone from sliding out in front of the thigh bone. Considering the anatomical location of the anterior cruciate ligament, it is very important for normal knee function, and disruption of this ligament will result in the early onset of joint degeneration. This article will discuss the causes, symptoms, investigation methods, and treatment options for ACL injury.

What Are the Anatomical Considerations of the Anterior Cruciate Ligament?

The knee is the modified hinge joint that connects the thigh bone to the shin bone. The dynamic stability of the knee joint is obtained by the four ligaments that hold the bones together. The major ligaments of the knee are;

• Lateral collateral ligament.

• Medial collateral ligament.

• Anterior cruciate ligament.

• Posterior cruciate ligament.

The ACL located inside the knee runs diagonally, connecting the thigh bone to the shin bone. It consists of two major bundles, namely the anteromedial and posterolateral bundles. The anterior cruciate ligament provides stability to the knee as it moves from flexion to extension.

What Are the Causes of an ACL Injury?

Injury to the anterior cruciate ligament commonly occurs from a fall from height with the knee in a bent position and the body rotating on the stationary foot. This results in abnormal internal rotation of the shin bone. Similarly, hyperextension of the knee with internal rotation of the tibia can cause anterior cruciate ligament injury. Most commonly, it occurs in combination with other damages, such as meniscal (tough cartilage acting as a shock absorber) injury.

• Anterior cruciate ligament injuries are reported to occur more commonly in people excessively indulging in sports activities such as basketball, baseball, football, etc.

• ACL injury also occurs as a result of repetitive stress to the knee, causing the ligament to lose its elasticity.

• This injury occurs more commonly in contact sports like football, but it can also occur in other non-contact sports.

What Are the Signs and Symptoms of an ACL Injury?

Clinical presentation of anterior cruciate ligament injury usually includes:

• Popping: The feeling of popping in the knee is one of the common symptoms of ACL injury.

• Giving away: A sudden weakness in the leg and the feeling of bone going out of its place are other common symptoms noted in patients.

• Approximately 75 % of patients with ACL injuries have the sign of instant effusion of the knee.

• Extreme pain in the injured knee.

• Inability to continue the activity which caused the injury.

• Loss of stabilityin the knee.

• The movement of the knee is limited.

How Is an ACL Injury Diagnosed?

The healthcare provider will diagnose the anterior cruciate ligament injury by doing a detailed and thorough history taking. The physician can mostly evaluate the diagnosis with the proper history of the patient. A detailed visual examination of the knee is performed, looking for the presence of effusion, discoloration, and ecchymosis. A thorough examination of the knee is performed when the patient is in a relaxed and comfortable position. Various clinical tests are performed to evaluate the diagnosis of anterior cruciate ligament injury. The most sensitive test for detecting instability of the anterior cruciate ligament is the Lachman test.

• Lachman test: With the patient’s knee in 20 to 30 degrees of flexion, the physician stabilizes the thigh bone with one hand and applies an anteriorly directed pressure to the proximal part of the shin bone with the other hand. Compared to the uninvolved knee, if there is an increased translation of the tibia, it indicates that the test is positive (ACL disruption).

• Anterior drawer test: The patient lies in a supine position with the knee bent at 90 degrees. The physician sits on the toes for anchor and pulls the knee forward to assess the anterior translation compared to the other knee. The test is considered positive if the anterior translation is more than six millimeters.

Radiographic imaging of the knee, such as Magnetic Resonance Imaging (MRI), is advised if the diagnosis is still inconclusive. They can provide a detailed view of the ligaments and cartilages, including the anterior cruciate ligament. MRI is generally used to confirm the diagnosis and to rule out other differential diagnoses.

What Are the Treatment Options for an ACL Injury?

The treatment option will depend on various factors, such as the age of the patient, the patient’s activity level, and the severity of the injury. Following the R.I.C.E method right after the injury can reduce pain and swelling,

• Rest after the injury for 48 hours and avoid activities causing knee pain.

• Ice is to be applied over the injured knee for 20 minutes four to eight times daily.

• Compression of the knee by wearing a tight band around the injured area can reduce the swelling.

• Elevation- Raising the knee above the waistline can help with the swelling.

The treatment options for ACL injury include non-surgical treatment and surgical treatment. Most active and young patients usually prefer the surgical option. At the same time, the non-surgical treatment option is usually reserved for elderly patients and people with a sedentary lifestyle.

Non-surgical treatment options include bracing and physical therapy. Physical therapy for the knee will help in restoring back the range of motion and improve its function. Physical therapy will focus more on hamstring, strengthening and core stability. Individuals with instability in the chronic ACL injury crossing more than six months are considered for surgical reconstruction. Wearing knee braces can provide extra stability and can be used after the reconstruction surgery to provide time for the ligaments to heal and prevent further injuries.

Surgical intervention is performed to reconstruct the torn anterior cruciate ligament. Common surgical techniques use the patient’s own tissues (autograft), usually the patellar or hamstring tendons, or a cadaver graft (allograft) to reconstruct the anterior cruciate ligament arthroscopically. Post-surgery, the patients usually take about six months to recover.

Conclusion

Anterior cruciate ligament injury is one of the common knee injuries seen in athletes and other sports persons. Recent studies suggested that untreated ACL injury can lead to a higher incidence of meniscus tears and, over time, it can lead to degenerative changes in the knee joint. An injured anterior cruciate ligament may require surgical intervention to regain the functions of the knee completely. An ACL injury can not be completely prevented in athletes, but they can reduce the risk of ACL injury by performing proper training techniques, adding strengthening exercises, and stretching properly before and after indulging in physical activity.