ACL tear: assessment and treatment— full professional article

What is the anterior cruciate ligament (ACL)?

On its own, the bony structure of the knee provides very little stability.

Most of the knee's stability comes from the ligaments inside and around the joint, which connect the femur (thigh bone) to the tibia (shin bone) across different planes of movement.

The ACL runs inside the knee and mainly prevents the tibia from sliding too far forward relative to the femur.

The ACL is the most commonly torn ligament in the knee.

The classic mechanism of an ACL tear is a pivoting injury, with or without contact, that combines a knee-inward (valgus) force with internal rotation, driving the tibia forward.

ACL tears are common in football, basketball, tennis, skiing, and similar sports. They frequently occur alongside other injuries, such as meniscus tears and cartilage damage.

What does an ACL tear mean for daily life?

After the initial painful, swollen phase settles, many patients function reasonably well, but the main long-term complaint is usually instability: the knee gives way when cutting, turning, walking on uneven ground, or returning to sport.

Some patients feel fine day to day and only notice the problem when they try to play sport, when the instability and swelling return.

Ongoing instability also raises the risk of further damage to the meniscus and cartilage over time.

Can an ACL tear be treated without surgery?

Rehabilitation focuses on strengthening and neuromuscular control. In young athletes, however, conservative care often fails to restore high-level rotational stability, so reconstruction is frequently discussed.

The decision is made together, weighing age, sporting demands, occupation, natural ligament laxity, and any meniscus or cartilage injury. When the knee keeps giving way despite committed rehabilitation, active patients usually benefit from surgical stabilization.

What happens during ACL reconstruction?

The goal is to restore the knee's stability by reconstructing the torn ligament. In active adults, the ACL is generally reconstructed rather than simply stitched back together.

A graft is used to take the place of the original ACL.

The graft tissue can be an autograft (from the patient) or an allograft (from a donor), taken from one of several sources.

Which grafts are used for ACL reconstruction?

Hamstring tendons, from the inner thigh and knee.

Bone-patellar tendon-bone, using the central third of the patellar tendon.

Quadriceps tendon autograft.

Allograft tendon from a screened donor, similar in concept to other donated transplant tissues.

The graft is prepared to the right length and diameter.

Tunnels are then drilled in the femur and tibia, and the graft is passed through and fixed at both ends to recreate the natural line of the ligament.

Graft choice balances donor-site discomfort, fixation strength, the risk of re-tear, and patient preference. Hamstring, bone-patellar tendon-bone, quadriceps tendon, and allograft each have well-established uses, and the right choice should follow an informed discussion with your surgeon.

What does recovery after ACL reconstruction involve?

Recovery takes time and involves extensive physiotherapy to rebuild range of motion, strength, and readiness to return to sport.

As a general rule, cutting and pivoting sports often require roughly 9 to 12 months before a safe return.

Some pain is expected in the early days after surgery. Pain medication and cryotherapy (cold therapy) help manage it.

Some surgeons use a brace in full extension for a short period to protect the knee, while others allow movement straight away. Protocols vary.

Many protocols allow full weight-bearing as tolerated soon after an isolated ACL reconstruction. Protected weight-bearing may be needed when an osteotomy, multi-ligament repair, or complex meniscus work is done at the same time.

If a meniscus repair is performed at the same time, the weight-bearing and bracing rules may be more restrictive for several weeks, with slower progression.