The anterior cruciate ligament (ACL) is one of the knee's most important stabilisers, and a tear is among the most common serious sporting injuries. Recognising it early means faster treatment and a better recovery.
1. A 'pop' at the moment of injury
Many people describe hearing or feeling a distinct pop as the ligament tears, usually during a sudden twist, pivot or awkward landing.
2. Rapid swelling
Significant swelling within a few hours is a red flag. It usually means bleeding inside the joint, which often accompanies an ACL tear.
3. A knee that gives way
A feeling that the knee is unstable or 'gives way' when you turn or change direction is a classic sign that the ACL is no longer doing its job.
4. Difficulty bearing weight
Pain and a sense of insecurity can make it hard to put full weight through the leg in the days after the injury.
5. Reduced range of movement
Swelling and pain often make it difficult to fully straighten or bend the knee.
What to do next
If you notice these signs, rest, ice and elevate the knee and arrange an assessment promptly. Early diagnosis protects the meniscus and cartilage and lets you start the right treatment quickly.