(HealthDay News) -- The knee's anterior cruciate ligament (ACL) can be stretched or torn during activities that strain the knee.
A torn ACL may require extensive therapy or surgery to repair it.
Here are primary symptoms of a torn ACL, courtesy of the U.S. National Library of Medicine:
- A loud popping noise as the knee it hit or twisted.
- Immediate, severe pain in the knee.
- Significant swelling of the knee in fewer than six hours after the injury.
- Difficulty walking or standing, and general weakness of the knee.