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Knee · condition guide

ACL tear

The ACL (anterior cruciate ligament) is one of the main ligaments that keep the knee steady. It usually tears in sport, during a sudden twist, change of direction or awkward landing. Not every tear needs an operation: the right plan depends on how unstable the knee feels and what you want to get back to.

Usual cause
A twist or awkward landing
Surgery needed?
Not always
Back to sport after surgery
About 9–12 months

For patients of Dr. Mandar Deb, orthopaedic surgeon, Kolkata. Based on AAOS OrthoInfo and NHS guidance. Sources

The injury

What is an ACL tear?

The ACL runs diagonally through the middle of the knee, from the thigh bone to the shin bone. It stops the shin bone sliding forward and helps control twisting, which is why it matters so much in sports that involve turning, cutting and jumping.

Most ACL tears happen without any contact: planting the foot and turning, stopping suddenly, or landing from a jump on a straight or twisted knee. Football, basketball, badminton and kabaddi are common causes. A direct blow, such as a tackle, can also tear it.

A tear can be a stretch (grade 1), a partial tear (grade 2) or a complete tear (grade 3). Complete tears are the most common. The meniscus, the cartilage or another ligament is often injured at the same time.

Signs

What does an ACL tear feel like?

  • A pop at the moment of injury, often felt or heard
  • Swelling within a few hours, usually within a day
  • The knee giving way, especially when you turn
  • Pain, and trouble fully bending or straightening the knee
  • Discomfort when walking

The pain and swelling often settle within a few weeks, and walking in a straight line can feel normal again. That doesn’t mean the ligament has healed. Going back to sport on an unstable knee can damage the meniscus and cartilage.

Diagnosis

How is it diagnosed?

Mostly by examination. How the injury happened tells a lot, and gentle tests comparing the injured knee with the other one show whether the shin bone moves forward more than it should. This is often enough to diagnose an ACL tear.

An X-ray doesn’t show ligaments, but it rules out a fracture. An MRI shows the ligament, the meniscus and the cartilage and helps plan treatment, but it isn’t always needed to make the diagnosis.

If you already have X-rays or an MRI, bring the films or CD and the report to your visit.

Treatment

Do I need surgery?

Without surgery

Physiotherapy rebuilds the thigh muscles, balance and control, sometimes with a brace for support. This can work well if the knee doesn’t give way in daily life and you don’t play pivoting sports or do heavy manual work. Partial tears with a stable knee often do well this way.

ACL reconstruction

A torn ACL heals poorly on its own, so it is usually rebuilt rather than stitched. In keyhole surgery the torn ligament is replaced with a graft, usually a tendon from your own knee or thigh (hamstring, patellar or quadriceps tendon), passed through small tunnels in the bone. More on ACL reconstruction

Surgery is usually advised for:

  • Active people who want to return to turning, cutting or jumping sports
  • Knees that keep giving way, even in daily life
  • Tears that come with meniscus damage or other ligament injuries

A knee that keeps giving way keeps getting hurt: most people with a long-standing unstable knee develop a meniscus tear within a few years. Children and teenagers need special care, because the bones are still growing. Preparing for surgery

Recovery

How long is recovery after ACL surgery?

Rehabilitation runs in phases with your physiotherapist. These are typical times; your own plan depends on the graft and any other injuries.

  1. Weeks 0–2Swelling down, the knee fully straight, the thigh muscle working again. Crutches as advised.
  2. Up to 3 monthsFull bending and a normal walk, then steady strengthening and balance work.
  3. 3–6 monthsMore strength, then running and jumping drills once your strength allows.
  4. 9–12 monthsBack to full sport after passing strength, balance and hop tests, not just the calendar.

See an orthopaedic doctor if…

  • You felt a pop and the knee swelled within hours
  • The knee gives way or feels unstable
  • You can’t fully straighten the knee, or it locks
  • Pain or swelling isn’t settling after a week or two

Emergency: a deformed knee, a leg you can’t put any weight on, or a foot that is cold, pale or numb. Go to the nearest emergency department now.

Questions

ACL FAQs.

What patients ask most about a torn ACL.

Can a torn ACL heal on its own?

A completely torn ACL doesn’t join back together by itself. Many people still get good everyday function back with physiotherapy; whether that is enough depends on how stable the knee feels and what you want to return to.

Can I walk with a torn ACL?

Usually yes, once the swelling settles. Walking in a straight line can feel normal. The problem shows when you turn, pivot or land, which is when the knee can give way.

Do I need an MRI for an ACL tear?

Not always. A careful examination often diagnoses an ACL tear. An MRI helps check the meniscus and cartilage and plan surgery.

How long after ACL surgery can I play sport?

Most people return to full sport around 9 to 12 months after surgery. The decision is based on strength, balance and movement tests passed during rehabilitation, not on the calendar alone.

Is ACL surgery keyhole surgery?

Yes. ACL reconstruction is done arthroscopically, through small cuts around the knee plus a small cut where the graft is taken. Many patients go home the same day or the next day.

Where can I see Dr. Mandar Deb for an ACL injury?

At his weekly OPDs in Newtown, Rajarhat, Dum Dum and South Kolkata, and in Basirhat twice a month. Book by calling the clinic; days, times and numbers are on the Clinics page.

References

Sources

This guide follows patient information from these organisations. It is general information; Dr. Deb’s advice for your own knee comes first.

  1. 01
    OrthoInfo, American Academy of Orthopaedic Surgeons (AAOS)

    Patient information written and reviewed by orthopaedic surgeons.

    Anterior Cruciate Ligament (ACL) Injuries ACL Injury: Does It Require Surgery?
  2. 02
    NHS, the UK’s National Health Service

    Public health guidance from the NHS website.

    ACL surgery
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