What You Need to Know About Knee Cruciate Ligaments Tear

What the cruciate ligaments do

Inside your knee joint are two strong ligaments that cross each other in an “X” shape. These are the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL).

They stabilise the knee by preventing the shinbone (tibia) from sliding too far forward or backward relative to the thighbone (femur). When one of these ligaments tears, the knee can feel unstable, especially during turning, pivoting, or sudden changes in direction.

ACL tears are far more common than PCL injuries.

How these injuries occur

Most ACL tears happen during sport and often without direct contact. Typical movements include:

• Sudden deceleration while running

• Rapid pivoting on a planted foot

• Landing awkwardly from a jump

• Changing direction quickly

You may hear or feel a “pop” at the time of injury. Swelling usually develops within a few hours due to bleeding inside the joint.

PCL injuries are less common and typically result from direct force to the front of the knee, such as in a car accident or heavy fall.

Symptoms you may notice

A cruciate ligament tear can cause:

• Immediate pain

• Rapid swelling

• Reduced ability to straighten or bend the knee fully

• A sense that the knee “gives way”

• Difficulty weight-bearing

Instability is often the key feature. Even once pain settles, the knee may feel unreliable during twisting movements.

Injury grading

Cruciate ligament injuries are classified by severity:

• Grade 1: Ligament stretched but intact

• Grade 2: Partial tear with some looseness

• Grade 3: Complete rupture with significant instability

A complete ACL rupture often requires specialist assessment to determine the best management plan.

How diagnosis works

Your GP or sports clinician begins with a detailed history and physical examination. Specific stability tests assess how firmly the shinbone moves relative to the thighbone.

An MRI scan commonly confirms the diagnosis and checks for associated injuries such as meniscus tears or cartilage damage.

Early management

In the first few days, reducing swelling and protecting the joint supports recovery. This may include:

• Relative rest

• Ice application

• Compression

• Elevation

Crutches or a brace may be used temporarily if walking feels unstable.

Treatment pathways

Management depends on your activity level, goals, and degree of instability.

Non-surgical management

Some people manage well without surgery, particularly if:

• The tear is partial

• Daily activities do not involve pivoting sports

• The knee feels stable after rehabilitation

Structured physiotherapy strengthens surrounding muscles — especially quadriceps and hamstrings — to improve functional stability.

Surgical reconstruction

Active individuals, competitive athletes, or those with persistent instability often consider ACL reconstruction.

This involves replacing the torn ligament with a tissue graft, commonly taken from the hamstring or patellar tendon. Surgery is performed arthroscopically (keyhole technique).

The decision is individual and should consider long-term knee health, sport demands, and lifestyle goals.

Recovery timeline

Rehabilitation is essential, whether surgery occurs or not.

Typical stages include:

• Early mobility and swelling control (first 6 weeks)

• Progressive strength and neuromuscular training (2–4 months)

• Return-to-running progression

• Return-to-sport testing

Full return to competitive pivoting sports usually takes 9–12 months to allow graft maturation and restoration of strength and coordination.

When to seek urgent review

Seek prompt medical attention if:

• The knee rapidly swells after injury

• You cannot bear weight

• The knee repeatedly collapses or locks

Early assessment improves clarity about diagnosis and reduces risk of secondary cartilage damage.

This article provides general health information only and does not replace medical advice. Please speak with your GP for personalised care.