Overview

The knee is stabilised by four key ligaments: the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), which cross through the centre of the joint, and the medial collateral ligament (MCL) and lateral collateral ligament (LCL), as well as a network of smaller structures , which run along its inner and outer sides. Together, these ligaments work to keep the knee stable through everyday movement and activity. A multi-ligament injury means two or more of these are torn at the same time, usually from a single high-force event.

What is the MCL and what are the types of MCL injury?

The MCL is the second most commonly injured of the four, after the ACL, and is frequently injured as part of a broader pattern of damage alongside an ACL rupture.

The medial collateral ligament is a strong, complex structure on the inner side of the knee, made up of two components: the superficial and deep MCL. The superficial portion is the larger of the two and plays the greater role in stabilising the joint. The MCL is active throughout the full range of knee movement and is an important stabiliser overall.

MCL injuries are classified into three grades:

  • Grade 1 — A sprain, with no actual tearing of the ligament.
  • Grade 2 — A partial tear of the ligament.
  • Grade 3 — A complete tear, which may occur at its attachment on the femur, through the middle of the ligament, or at its insertion on the tibia.

What are the symptoms of an MCL injury?

Symptoms of an MCL injury typically depend on the severity of the tear, but commonly include:

  • Pain and tenderness along the inner side of the knee
  • Swelling, which may develop gradually rather than immediately
  • A feeling of the knee giving way or being unstable, particularly with more severe tears
  • Bruising on the inner aspect of the knee
  • Discomfort or difficulty when bending or straightening the knee fully

MCL Treatment

Good news first: the MCL is one of the knee's best natural healers, so most isolated injuries recover well without surgery. Reconstruction is generally reserved for severe, complete tears — or when the MCL is injured alongside other ligaments and ongoing instability is expected without surgical support.

When surgery is needed, the goal is to restore the ligament that stops your knee opening up on the inner side. Depending on the injury, this means either repairing the ligament back to its original attachment point, or reconstructing it with a tendon graft, precisely anchored into the femur and tibia to recreate its natural alignment and tension.

What is the PCL and what are the types of PCL injury?

The posterior cruciate ligament is the second of the two cruciate ligaments at the centre of the knee, working alongside the ACL. It's injured less often than the ACL, and its main role is to prevent the tibia from moving too far backwards beneath the femur.

PCL injuries are most commonly associated with dashboard injuries sustained in road traffic accidents, where the bent knee strikes the dashboard on impact, forcing the tibia sharply backwards and rupturing the ligament. However, PCL injuries can also occur through a number of other mechanisms.

What are the symptoms of a PCL injury?

A PCL injury can present quite differently to other ligament injuries, with symptoms that are sometimes more subtle. These can include:

  • Pain at the back of the knee, particularly when kneeling or descending stairs
  • Swelling, which usually develops soon after injury
  • Stiffness and a reduced range of movement in the knee
  • A sensation of instability, especially when walking on uneven ground or changing direction
  • Difficulty bearing full weight through the affected leg in more significant injuries

PCL Treatment

The PCL is tougher than its more famous counterpart, the ACL, and isolated injuries can sometimes be managed without surgery. But when the PCL is significantly torn — especially alongside other ligament damage — reconstruction is often needed to restore stability and protect the knee from long-term joint damage.

The procedure is performed arthroscopically, using keyhole techniques to minimise trauma to the surrounding tissue. The damaged ligament is replaced with a new graft, typically donor tendon tissue. Precisely drilled tunnels through the tibia and femur recreate the ligament's natural position, and the graft is secured at each end — restoring its key role in stopping the shin bone sliding backwards beneath the thigh bone.

What is the LCL and what are the types of LCL injury?

The lateral collateral ligament (LCL) is a strong band of tissue running along the outer side of your knee, connecting the thigh bone (femur) to the smaller lower leg bone (fibula). Its job is to stop the knee from opening up excessively on the outside — think of it as one of the knee's key side stabilisers.

LCL injuries are usually graded by severity:

  • Grade I (mild) — the ligament is stretched but not torn, with minimal instability.
  • Grade II (moderate) — a partial tear, with some looseness and instability in the knee.
  • Grade III (severe) — a complete tear, often causing significant instability, and frequently associated with damage to the wider posterolateral corner — the group of structures that work alongside the LCL to control rotational stability.

LCL injuries typically result from a direct blow to the inner side of the knee, or a significant twisting injury, and are often seen alongside other ligament injuries in higher-energy trauma.

What are the symptoms of a LCL injury?

Common symptoms of an LCL injury include:

  • Pain and tenderness along the outer side of the knee
  • Swelling, which may develop quickly after the injury
  • Bruising on the outside of the knee
  • A feeling of instability or "giving way", particularly when walking on uneven ground or changing direction
  • Stiffness, making it difficult to fully bend or straighten the knee
  • In more severe injuries, a sensation of the knee opening up on the outer side, or numbness/tingling if nearby nerves are affected

LCL Treatment

Unlike some other knee ligaments, LCL and posterolateral corner injuries tend to cause significant instability — meaning surgery is more often needed. Repair or reconstruction is typically recommended for complete tears, especially where instability is present or other ligaments are also affected.

The approach depends on the nature and timing of the injury. When caught early and tissue quality allows, a direct repair — reattaching the ligament to its original bony attachment using suture anchors — may be possible. For chronic injuries or more extensive damage, reconstruction is preferred, using a tendon graft to rebuild the ligament and restore resistance to the knee opening up on its outer side.

Frequently asked questions

Diagnosis starts with a careful examination checking the stability of each ligament individually, plus circulation and nerve function in the leg. An MRI maps out exactly which ligaments — and any accompanying cartilage or meniscus damage — are involved, which shapes the treatment plan.

Not necessarily. Some ligaments, like the MCL, often heal reasonably well with bracing and time because of their good blood supply. Others, like the ACL and PCL, generally need surgical reconstruction to restore stability. Your surgical plan is built around which specific ligaments are involved.

Both approaches are used, depending on the injury. Surgeons often wait for initial swelling to go down and for range of motion to improve before operating. Mr Barkatali prefers to reconstruct all torn ligaments in a single surgery where possible to minimise the number of surgical procedures for the patient, however multiple procedures may be required if the injury is especially complex.

Any knee injury involving significant swelling, a feeling that the joint is unstable in multiple directions, or inability to bear weight should be evaluated promptly by a knee specialist. Numbness, coldness, or pale skin in the foot after a knee injury needs emergency attention right away.

Please use the link below to make an enquiry and we will be in touch to book an initial appointment with Mr Barkatali.

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