The ACL (anterior cruciate ligament) can be torn if the knee is pulled or twisted in an unnatural way. Injuries to the ACL are especially common in sports where side-to-side or pivoting movement of the knee is required; soccer, basketball, skiing, and football are frequent culprits. An injured ACL is associated with the following symptoms:
- An audible pop or snapping upon injury
- Immediate and sustained swelling in the knee
- Instability in the knee that can cause it to give out
- Inability to bear weight
- Significant pain that does not diminish in the hours following the injury
- A feeling of fullness in the knee
Elderly, less active patients may not require surgery following an ACL injury—if the overall stability of the knee is healthy and the patient has a low activity level, the physician may recommend non-surgical options. For young athletes, however, surgery is usually needed. The torn ligament must be replaced with a tissue graft, which will then form the base for the new ligament to grow on.