“An ACL injury is the tearing of the anterior cruciate ligament (ACL) — one of the major ligaments in your knee. ACL injuries most commonly occur during sports that involve sudden stops, jumping or changes in direction — such as basketball, soccer, football, tennis, downhill skiing, volleyball and gymnastics.

Many people hear or feel a "pop" in the knee when an ACL injury occurs. Your knee may swell, feel unstable and become too painful to bear weight.

Depending on the severity of your ACL injury, treatment may include rest and rehabilitation exercises to help you regain strength and stability or surgery to replace the torn ligament followed by rehabilitation. A proper training program may help reduce the risk of an ACL injury.

Signs and symptoms of an ACL injury usually include:

• A loud "pop" or a "popping" sensation in the knee

• Severe pain and inability to continue activity

• Swelling that begins within a few hours

• Loss of range of motion

• A feeling of instability or "giving way" with weight bearing

Programs to reduce ACL injury include:

• Exercises that strengthen leg muscles, particularly hamstring exercises, to ensure an overall balance in leg muscle strength

• Exercises to strengthen the core: hips, pelvis and lower abdomen

• Training and exercise for proper techniques and knee position in jumping and landing

• Training to improve techniques for pivoting and cutting

https://www.mayoclinic.org/diseases-conditions/acl-injury/symptoms-causes/syc-20350738 REF Google images