This injury usually occurs when the knee is twisted or hyper-extended. Usually the tearing of the ligament occurs with a sudden directional change with the foot fixed on the ground or when a deceleration force crosses the knee. This type of injury is common in soccer, skiing, football, and other sports with lots of stop-and-go movements, jumping, or weaving. Like any other body part, the ACL becomes weaker with age and is more prone to damage. Sometimes the force is quite small.
Pain and Symptoms
Associated with the injury the person will often hear a ‘pop’, ‘crack’, or feel a ‘snap’ within the knee. The knee may feel like it went out of place. It us usually painful and rarely allows the person to continue with their activity.
The knee often swells within the first few hours of the injury. This may be a sign of bleeding inside the joint. Swelling that occurs rapidly is usually a sign of a serious knee injury.
Giving way or instability of the knee particularly with twisting is common.
Restricted movement and pain, particularly in the first few weeks following the injury is also common. The pain usually gradually settles and sometimes the knee feels normal by around 8 weeks.
Because the ligament protects other structures such as the menisci in the knee when it is damaged, these structures also can be injured. The injury to the Anterior Cruciate Ligament is often accompanied by a “bone bruise” or micro-trabecular fracture of the tibia and femur. The Medial Ligament is also often injured.
The diagnosis is made after taking a thorough history and gently examining the knee. The Lachman’s test is the most sensitive clinical test but still misses some of these injuries. If an injury to the anterior cruciate ligament is suspected further imaging will be required with the aid of an MRI. If the ACL is torn a specialist orthopaedic surgeon’s opinion is required.
Initial management will focus on decreasing swelling, increasing movement and strengthening the leg and hip muscles. Even in situations where surgery is required this is important.
The role of surgery is to restore the mechanical stability to the knee. The graft (which can be taken from a variety of sources, with the hamstring tendon the most common in Australia) takes around 6 months to fully strengthen. Return to sport takes approximately 12 months.
A disrupted cruciate ligament increases the risk of re-injury to the knee due to the instability.
It also increases your risk of developing osteoarthritis once again because of the lack of stability in the knee.
This is a lengthy process that needs to be guided by an experienced Physiotherapist. It involves a progressive series of exercises, starting gently in the early post-operative phase, and progressing to sports-specific exercises in the later stage. The program is designed to restore the movement to the knee, strength to the surrounding muscles and movement control to help prevent re-injury.