Other ligament Injuries

What is it?

Ligaments are structures that span a joint within the body providing stability throughout range of movement to that joint.  The knee has a number of important stabilising structures but there are 4 main stabilising ligaments in the knee:

  1. The anterior cruciate ligament
  2. The posterior cruciate ligament
  3. The medial collateral ligament
  4. The lateral collateral ligament

Damage to one or more of these ligaments and/or other associated stabilising structures can lead to significant instability within the knee and sometimes require surgery in combination with physiotherapy to ensure the best long term outcome after injury. 

Anterior cruciate ligament

The ACL is a strong spiral shaped ligament that runs from the tibia to the lateral wall of the intercondylar notch of the femur.  The ACL prevents the tibia from sliding forwards on the femur and from rotating below it in an extreme fashion.  This is the most commonly injured ligament within the knee. 


Posterior cruciate ligament

The PCL is the largest ligament within the knee and runs from the middle of the posterior aspect of the tibia up towards the medial wall of the intercondylar notch on the femur.  The PCL prevents the tibia from sliding too far backwards on the femur and similarly therefore prevents the femur from sliding too far forwards on the tibia particularly on activities and descending stairs and slopes.  The majority of posterior cruciate ligament injuries are part of a more significant knee injury involving other structures and ligaments as well.


Medial collateral ligament

The MCL runs from the femur to the tibia on the inside of the knee.  It is wide and flat and runs in the layers outside the capsule of the knee.  It prevents the knee from buckling inwards (valgus/knock kneed).  It is often injured in sports where the patient sustains a blow to the lateral side of the knee forcing the knee into a valgus position. 

Lateral collateral ligament

The LCL is on the outside of the knee and is a rope like structure passing from the femur to the fibular head.  It provides stability to the lateral side of the knee preventing it opening up and allowing the knee to collapse into a varus (bow legged) position.  The lateral collateral ligament is part of an anatomic region known as the posterolateral corner (PLC).  This includes other structures such as the popliteus muscle, the arcuate ligament and the popliteofibular ligament.  The LCL and PLC act in combination to provide stability to the lateral side of the knee and prevent excessive external rotation of the tibia on the femur.  The posterolateral corner can form an important part of multi-ligament injuries and failure to recognise an injury to this area can lead to worse outcomes in anterior cruciate ligament reconstruction. 

Why does it occur?

Ligament injuries within the knee are typically as a result of sporting injuries.  These can vary from fairly minor non-contact twisting injuries where often the anterior cruciate ligament is injured, for instance skiing or playing football, to more significant high energy injuries such as road traffic accidents or rugby tackles where often a combination of ligament injuries are seen.  If the knee is stressed into a position outside its normal envelope with significant force, ligaments can exceed their maximal tensor strength and rupture.  When lesser force is transmitted to the ligaments, ligament sprains or partial ruptures can occur most commonly to the medial collateral ligaments.


What are the symptoms?

The symptoms of ligament injuries can vary hugely dependent on the severity and combination of ligament injuries. 

Anterior cruciate ligament ruptures.


Posterior cruciate ligament ruptures

Isolated injury to the posterior cruciate ligament is rare representing approximately 10% of PCL tears.  In isolation rupture of the posterior cruciate ligament leads to a Sag Sign where the tibia sits further back in relation to the femur than normal.  It often does not go on to cause huge functional instability in the knee and can quite commonly be treated non-operatively perhaps with the assistance of a brace to support the posterior cruciate ligament whilst it heals under the guidance of an experienced physiotherapist.  However, in some cases if significant instability ensues, a reconstruction of the posterior cruciate ligament can be recommended.  Symptoms of a posterior cruciate ligament injury can often be more severe if it is a combination of a multi-ligament injury from a knee dislocation. 

Medial collateral ligament injuries

Symptoms from medial collateral ligament tears vary dependent on the severity of the injuries.  In grade 1 injuries or sprains typically symptoms are of pain down the medial aspect of the knee particularly on weight bearing or if the knee is forced into valgus.  More severe injuries (grade 3) can lead to significant opening up of the medial side of the knee leading to the leg collapsing into valgus through the gait cycle.


Lateral collateral ligament/posterolateral corner injuries

Symptoms relating to a complete rupture or significant injury to the lateral side of the knee often manifests as a feeling of instability whilst walking.  Typically these also represent part of a multi-ligament injury leading to significant pain, swelling and instability within the knee.


How is it diagnosed?

Your surgeon will take a thorough history of the mechanism of injury and fully examine your knee.  It is often possible to pick up damage to the major structure of the ligaments of the knee with a variety of tests looking at aspects of knee stability.  Often an x-ray will be required to rule out any significant associated fracture or osteochondral injury and an MRI scan is normally undertaken to fully elicit the combination of ligament injuries. 

How is it treated?

The treatment of ligament injuries is usually dependent upon the severity and pattern. 

Anterior cruciate ligament injuries. 

Posterior cruciate ligament injuries

Isolated posterior cruciate ligament injuries represent approximately 10% of PCL tears and can often be managed non-operatively under the supervision of physiotherapists, potentially with the use of a brace to support its healing.  In the majority of cases this will provide sufficient stability to the knee to avoid any surgical interventions.  On the occasions that this fails, surgical reconstruction of the posterior cruciate ligament can be undertaken. 

Medial collateral ligament injuries

Partial MCL injuries or MCL sprains almost always recover fully with non-operative management.  In more severe injuries supporting the knee with a brace to allow it to heal appropriately is often required.  There are rare patterns of medial collateral ligament injuries, such as tibial avulsions or MCL injuries in part of a multi-ligament setting, where MCL reconstruction may be required.  Occasionally as part of a combined anterior cruciate ligament and medial collateral ligament injury supporting the medial collateral ligament with an internal brace to allow it to heal more effectively is recommended to give optimal outcome from the anterior cruciate ligament reconstruction. 

Lateral collateral ligament/posterolateral corner injuries

In the vast majority of cases injuries to the lateral collateral or posterolateral corner represent part of a multi-ligament injury and lead to significant functional instability within the knee.  In this setting reconstruction of the lateral collateral ligament and/or posterolateral corner using a variety of techniques from direct repair to artificial ligament reconstruction is normally recommended.


Multi-ligament injuries to the knee (knee dislocation)

These represent severe injuries to the knee joint and are often as a result of major trauma.  A huge number of combination of injuries can be sustained such as ACL + PCL or ACL + PLC or in the worst case scenario ACL + PCL + MCL + LCL + PLC.  This usually causes severe instability within the knee and normally does require surgical reconstruction.  These represent quite complex and involved surgery and should be undertaken by a specialist knee surgeon with an interest in major ligament injuries.  The precise surgical approach is dependent upon the pattern of injury.