Ligament injuries of the knee commonly occur during contact sports such as football, hockey, basketball, rugby, etc. Road traffic accidents can also cause these injuries.

Ligaments of the knee that can sustain injury include

    1. Medial collateral ligament (MCL)
    2. Lateral collateral ligament (LCL)
    3. Anterior cruciate ligament (ACL)
    4. Posterior cruciate ligament (PCL)

Before reading further it would be good to review the section on Knee Anatomy(skip if you have already done so).

First we will look into collateral ligament injuries.

Mechanism of injury. MCL in injured by a force applied to the outer aspect of the knee joint, that tends to wedge open the knee joint on the inside, with the foot firmly planted on the ground. Lateral collateral ligament (LCL) is injured by the same way but with the force acting on the inner aspect of the knee joint.

If the same force continues to act then the cruciate ligaments can also get injured.

Collateral ligament injuries can be classified into three types according to the severity of the injury. Testing is done by reproducing the mechanism of injury by the examiner and assessing the opening of the joint.

  • Grade 1. - Opening of less than 5mm
  • Grade 2. - Opening between 5 to 10mm
  • Grade 3. - Opening beyond 10mm

Diagnosis is established by history and clinical examination.

  • Patient will give a history of trauma followed by pain over the injured ligament.
  • Swelling may be present (Grade 2).
  • Patient may have had a sensation of tearing at the time of injury (Grade 3).
  • Patient may have a feeling of weakness or instability in the knee joint (the joint seems to buckle during walking).
  • Tenderness is present over the torn ligament.

X rays of the knee are normal unless the ligament has separated from its attachment to bone taking with it a bony chip.

MRI scan can show the actual site of the tear. It is helpful in assessing the grade of injury and the integrity of other ligaments.

Treatment is according to the grade of the injury and the presence of associated injury to the ACL.

Grade 1 and 2 injuries rarely involve the ACL. They are treated as follows...

  • As instability is not a problem in these injuries hence treatment is directed to reduction of pain and inflammation and early return to normal activity.
  • Anti-inflammatory medication and ice is used.
  • Activity is restricted till the patient is comfortable.
  • A knee cap or brace can be used to protect the knee from further injury.
  • After pain has completely subsided exercises are initiated to regain strength.
medial collateral ligament tear

In grade 3 injuries the integrity of the cruciate ligaments is ascertained with a MRI scan or Arthroscopy.

If the cruciate ligaments are intact then treatment is same as grade 1 and 2 except that brace use may be required for a longer time. If cruciate ligaments are torn then surgery is done.

This is a x ray of a young male who injured his medial collateral ligament when he was trying to sit on his bike wearing a tight trouser. He lost balance and fell down. His x ray shows avulsion of the attachment of the medial collateral ligament on the femur (small red arrow). As all the other ligaments were intact hence he was treated non-operatively with a knee brace, analgesics and anti-inflammatory medication.

Cruciate Ligament Injuries

rupture of anterior cruciate ligament

Mechanism of injury for ACL is the same as MCL. ACL ruptures when the force continues to act after rupturing the MCL. Hyperextension of the knee joint can also rupture the ACL.PCL is ruptured by a force pushing the leg behind with the foot firmly planted on the ground.

Symptoms include

  • severe pain and swelling
  • knee joint feels weak
  • limping is present

Diagnosis is by history and examination. Various tests are used by the examiner to determine ligament rupture. In these tests the examiner manipulates the affected limb in various positions of flexion extension and tries to feel for abnormal mobility of the tibia as compared to the opposite side.

These tests include

  • Lachman test
  • Anterior Drawer test
  • Posterior Drawer test
  • Reverse pivot shift test

Investigations done to evaluate the integrity of ACL and PCL include Arthroscopy and MRI. Visualization of PCL is difficult on Arthroscopy and MRI both.

Classification of cruciate ligament injuries is by the degree of translation of the tibia while performing Drawer tests.

  • Grade 1 - translation less than 5mm
  • Grade 2 - translation between 5 to 10mm
  • Grade 3 - translation between 10 to 15mm
  • Grade 4 - translation more than 15mm

Treatment of ACL injury

  • Isolated partial or complete tear of ACL in a non athletic person can be treated non-operatively by anti-inflammatory medication, plaster cast or knee brace and exercises.
  • Complete ACL tear (with or without other ligament tears) in an active athlete is treated by Arthroscopic reconstruction of the ligament.

Treatment of PCL injury

  • PCL is separated with a large bony fragment then the bone piece is fixed with screws. This automatically fixes the ligament.
  • Grade 1 and 2 PCL tears are treated by anti-inflammatory drugs, use of knee brace and rehabilitation exercises.
  • Grade 3 tears are treated by ligament reconstruction.

Frequently Asked Questions

When should surgery be undertaken for cruciate injury?

In active athletes surgery should be done with in a few days of injury.

How are cruciate ligaments repaired?

Cruciate ligaments are not repaired they are reconstructed. This means that the ligament is not joined end to end by sutures but the whole ligament is formed from other tissues of the body (patellar tendon usually) and fixed into the place of the original ligament.

What are the complications of this surgery?

Main complications of this surgery are residual laxity (looseness) in the reconstructed ligament and loss of some movement.

How long does it take to return to active sports after cruciate ligament injury?

It can take between 2 to 6 months depending on the severity of the injury.

Can a non athletic person with a cruciate tear require surgery?

Rarely he may require surgery if the knee is symptomatic continuously.

I hope the information provided was helpful. If you have any query about ligament injuries you can ask me at the contact me page.

This page was last updated on 21st January 2009.

Other causes of knee pain include...

Knee Osteoarthritis

Knee Bursitis

Meniscal Injury

Knee Fracture

Patella Fracture

Tibial Plateau Fracture

Osgood Schlatter Disease

Knee Anatomy

Knee Replacement Surgery

Go back to Knee Pain from Ligament Injuries


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