ACL Tear

An ACL tear is a partial or complete injury to the anterior cruciate ligament inside the knee.

The ligament helps control forward movement and rotation between the thigh bone and shin bone. A tear can happen during sport, a fall, or a sudden change of direction, and it may occur with injuries to other knee structures.

Knee giving way is a very common presentation of an ACL tear. Pain, swelling that develops soon after injury, reduced movement and difficulty bearing weight may also occur. Some people describe a popping sensation at the time of injury, although its absence does not exclude a ligament injury. Explore [Knee Pain](/symptoms/knee-pain/) and [Knee Swelling](/symptoms/knee-swelling/) for related information.

A non-contact tear may occur when the foot is planted and the body turns, stops or lands awkwardly. Contact to the outside of the knee can force the joint beyond its normal position. The injury can be isolated or combined with meniscus, cartilage or other ligament damage.

Swelling and stiffness often limit movement soon after the injury. As these settle, instability may become clearer during turning, descending stairs or sport. Some people manage daily life with rehabilitation, while others need treatment that supports demanding pivoting activities. The knee can be reassessed as strength and movement return.

Activities involving cutting, pivoting, jumping and rapid deceleration place high demands on the ACL. Previous knee injury, reduced leg strength, limited movement control and fatigue may affect how the knee responds to a landing or change of direction.

Assessment includes the injury mechanism, swelling pattern, range of motion, walking, and ligament stability tests. Magnetic resonance imaging can show the ACL and associated meniscus or cartilage injury. X-rays may be used to check for a bone injury, since they do not show the ligament itself.

Early care focuses on controlling swelling, restoring knee movement and rebuilding strength. [Sports Physiotherapy](/treatments/physiotherapy-and-rehabilitation/sports-physiotherapy/) may address balance, landing control and sport-specific movement. [Knee Bracing](/treatments/non-surgical-orthopedics/knee-bracing/) can provide temporary support for selected activities.

Before surgery, [Prehabilitation](/treatments/physiotherapy-and-rehabilitation/prehabilitation/) can improve movement and muscle readiness. [ACL Reconstruction](/treatments/sports-and-arthroscopic-surgery/acl-reconstruction/) may be considered when instability, associated injuries or activity goals make ligament reconstruction appropriate. A supervised [Return-to-Sport Programme](/treatments/physiotherapy-and-rehabilitation/return-to-sport-programme/) follows either pathway.

Until the knee is assessed, avoid twisting, pivoting and activities that repeatedly cause giving way. Keep within the movement and weight-bearing limits provided by your clinician. Strength work should progress from controlled exercises to changing-direction tasks only when stability and control have improved.

Repeated episodes of giving way can damage other knee tissues and make everyday movement less predictable. Ongoing weakness and stiffness may also delay a return to work or sport. Longer-term joint wear can occur after significant knee injury, so persistent instability deserves review; [Knee Osteoarthritis](/conditions/knee-osteoarthritis/) is a separate condition that may be discussed in follow-up.

Training programmes that practise landing, deceleration, balance and controlled cutting can improve movement habits. Keep leg and hip strength consistent, warm up before intense activity, and increase sport demands gradually after a break or injury.

An orthopaedic knee clinician and sports physiotherapist can combine stability testing with your work and sport goals. Bring the injury date, swelling timing, previous knee problems and examples of when the knee gives way.