An Anterior Cruciate Ligament (ACL) injury is the tearing of a large ligament inside your knee joint. The ACL, one of two ligaments that cross in the middle of the knee, connects your thighbone (femur) to your shinbone (tibia) and helps stabilize your knee joint.
An ACL injury most commonly occurs during sports that involve sudden stops and changes in direction. The ligament may tear when you slow down suddenly to change direction or pivot with your foot firmly planted, twisting or hyperextending your knee. Landing awkwardly from a jump can also injure your ACL, as can falls during downhill skiing. A football tackle or motor vehicle accident also can cause an ACL injury. However, most ACL injuries occur without such contact.
Women are significantly more likely to have an ACL tear than are men participating in the same sports. Women tend to have more significant muscle imbalance around the hip and pelvic region which leads to increased stresses on the knee joint during sport.
At the time of an ACL injury, signs and symptoms may include:
- A loud “pop” sound
- Severe pain and inability to continue activity
- Knee swelling that usually worsens for hours after the injury occurs
- A feeling of instability or “giving way” with weight bearing
Diagnosis and Treatment
A chartered physiotherapist or orthopaedic doctor can help diagnose an ACL tear from the history of the injury and a number of examination techniques of the knee. Often the diagnosis can be made on the physical examination alone, but you may need tests such as an MRI to outrule other causes and to determine the severity of the injury.
Depending on the severity of the injury and other factors such as your age and lifestyle, surgery may or may not be required. The younger sporting population tend to have more immediate surgery which involves a rehabilitation period of up to one year. Others can manage well with conservative treatment in the form of intensive physiotherapy to strengthen the hip and lower limb muscles along with balance exercises.