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Other knee ligament injury (PCL, MCL, LCL)

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Posterior cruciate ligament (PCL)

  • What is the PCL?

    The PCL (posterior cruciate) ligament is one of main stabilising ligaments within the knee. It connects the femur (thigh bone) and tibia (shin bone), and prevents backwards movement of the tibia. It works in conjunction with the ACL to provide front-to-back stability of the knee. It is injured approximately 30 times less frequently than the ACL.

  • Injuring the PCL requires a lot of force, and so contact injuries are the main cause:

     

    • Road traffic accidents - direct impact of the tibia on the dashboard in head on collisions

    • Sports - contact sports with impact from the front

    • Falls from height, or hyperextension injuries 

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    Isolated tears to the PCL are relatively uncommon, and rupture usually occurs in combination with injury to the collateral ligaments (MCL / LCL), or ACL.

  • A PCL injury is diagnosed through:

    • Physical examination to assess the swelling, range of movement, and front-to-back stability of the knee

    • Imaging of the knee using an MRI (magnetic resonance imaging) scan

    1. Non-Surgical (Conservative) Treatment 
      Most isolated PCL injuries can be treated non-surgically in a brace which pulls the tibia forward to prevent sag. It is essential to fit the brace as soon as possible, and it needs to be worn 24/7 for 3 months. Rehabilitation of the knee is guided by a physiotherapist, to restore stability and strength. 

    2. ​Surgical Treatment (PCL Reconstruction)
      Reconstruction of the PCL is indicated if there is persistent instability following non-surgical treatment, high grade injuries, or when combined with other knee ligament (multi-ligament) injuries. Reconstruction uses a ‘graft’ (hamstring tendons or donor tissue (allograft)) to   the injured ligament, which is anchored in the tibia and femur. It is performed arthroscopically (keyhole) assisted.

Medial collateral ligament (MCL)

  • What is the MCL?

    The MCL (medial collateral ligament), is a ligament complex on the inner side of the knee that provides side-to-side stability in combination with the LCL. It has various parts that prevent instability of the knee in different positions. 

  • The MCL is injured when there is excessive stress or force applied to the outside of the knee, causing the inside (medial side) of the knee to stretch or tear. It can be from a contact, or non contact injury:

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    • Contact injury - This is the most common cause, and often occurs in contact sports. It results from a direct force on the outer side of the knee. It is often combined with other knee ligament injuries.

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    • Twisting or pivoting injury - This happens when the foot os planted and the body turns suddenly, occurring in sports such as skiing, basketball or football. It often occurs with an accompanying ACL injury.

  • An MCL injury is diagnosed through:

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    • Physical examination to assess the swelling, range of movement, and side-to-side and rotational stability of the knee

    • Imaging of the knee using an MRI (magnetic resonance imaging) scan

  • The vast majority of MCL injuries are treated non-surgically. It is important that a hinged knee brace is fitted as soon as an MCL injury is suspected, and later diagnosed. The brace should be worn  24 hours per day, for 6 weeks. This supports the ligament, and allows it to heal without stretching. Surgery is indicated in some circumstances:

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    • When the ligament pulls off the tibia (shinbone avulsion), early repair is sometimes indicated

    • When significant (grade 3) side-to-side instability persists despite proper treatment in a brace

    • When combined with other knee ligament injuries, and therefore contributing to ‘compound’ knee laxity

  • The treatment of a PLC injury must take into account many factors including symptoms, objective instability, lower limb alignment and rehabilitation aspirations. They will often require repair and/or reconstruction, and this is often combined with multiple other procedures to the knee. PLC injury and treatment is a complex pathology, and so should be discussed with a specialist knee surgeon.

Lateral collateral ligament LCL (posterolateral corner)

  • What is the LCL?

    The LCL (lateral collateral ligament) is a ligament on the outer side of the knee that provides side-to-side stability, in combination with the MCL. Unlike the MCL, it only provides stability with the knee in a relatively straight position. Therefore there are other structures that also contribute to stabilising the posterolateral part of the knee.

  • The PLC (posterolateral corner) is the outer-back part of the knee. It consists of the LCL, and other tendons and ligaments (popliteus, popliteofibular ligament, biceps femoris tendon) that stabilise the knee to resist side-to-side force, and rotation.

  • A PLC rupture is a significant injury, and is often seen in combination with other knee ligament injuries or tibial plateau (joint surface) fractures.

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    Direct blow to the anteromedial Knee

    • A force to the front-inside of the knee while the foot is planted can push the knee into hyperextension and varus (outward bowing), stressing the PLC. This is common in contact sports or motor vehicle accidents.

    Hyperextension injury

    • When the knee is forcefully extended beyond its normal range, especially if combined with external tibial rotation. It often occurs in football, skiing, or gymnastics.

    Twisting or pivoting with the poot planted

    • Sudden rotational movements (especially external rotation) with a fixed foot can cause PLC structures to tear, often along with ACL or PCL injuries.

    Varus stress with knee flexion

    • A blow or force pushing the knee outward while it is bent can strain the lateral stabilisers. This is seen in sports that involve quick cutting or awkward landings.

  • A PLC injury is diagnosed through:

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    • History - A careful exploration of the causing mechanism will often raise suspicion of a PLC injury, which can then be examined and imaged for

    • Physical examination to assess the swelling, range of movement, side-to-side and rotational stability of the knee

    • Imaging of the knee using an MRI (magnetic resonance imaging) scan, though this is not always reliable in chronic (long-term) injuries

  • The treatment of a PLC injury must take into account many factors including symptoms, objective instability, lower limb alignment and rehabilitation aspirations. They will often require repair and/or reconstruction, and this is often combined with multiple other procedures to the knee. PLC injury and treatment is a complex pathology, and so should be discussed with a specialist knee surgeon.

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