Posterior Tibial Dislocation: Causes, Symptoms, Diagnosis, Treatment, and Recovery

What is posterior dislocation of the tibia?

Posterior dislocation of the tibia refers to a severe knee injury where the tibia (shin bone) is displaced backward relative to the femur (thigh bone), often resulting from high-energy trauma and typically involving significant damage to the knee's stabilizing ligaments.

Anatomy of the Knee Joint

To understand a posterior tibial dislocation, it's essential to first grasp the basic anatomy of the knee. The knee is a complex hinge joint formed by the articulation of three bones: the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). Stability in the knee is primarily provided by a network of strong ligaments:

• Cruciate Ligaments: The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) cross within the knee joint, preventing excessive forward and backward motion of the tibia relative to the femur. The PCL specifically resists posterior translation of the tibia.
• Collateral Ligaments: The medial collateral ligament (MCL) and lateral collateral ligament (LCL) provide stability against side-to-side forces.
• Menisci: C-shaped cartilage pads that act as shock absorbers and help distribute weight within the joint.

Defining Posterior Tibial Dislocation

A dislocation occurs when the bones that form a joint are forced out of alignment. In the case of a posterior tibial dislocation, the upper end of the tibia (tibial plateau) is forcefully pushed backward, completely losing its normal articulation with the femoral condyles. This is a critical injury because it signifies profound instability of the knee joint, almost invariably involving extensive damage to multiple ligaments, most notably the posterior cruciate ligament (PCL), which is the primary restraint against posterior tibial displacement.

Causes and Mechanisms of Injury

Posterior tibial dislocations are high-energy injuries, meaning they require a significant amount of force to occur. They are relatively rare but devastating. Common mechanisms include:

• Dashboard Injury: This is a classic mechanism, often seen in motor vehicle accidents where the occupant's knee strikes the dashboard, driving the tibia backward.
• Direct Blow to the Anterior Tibia: A direct force applied to the front of the shin bone, such as during contact sports (e.g., a football tackle), can push the tibia posteriorly.
• Hyperflexion Injury: Extreme bending of the knee, often combined with a rotational or posterior force.
• Hyperextension Injury: While less common for pure posterior dislocation, severe hyperextension of the knee can lead to a complex dislocation pattern that includes posterior displacement.

Given the immense force required, these dislocations are frequently accompanied by other serious injuries, including:

• Multiple Ligament Tears: Often involving the PCL, ACL, and one or both collateral ligaments.
• Meniscal Tears: Damage to the cartilage pads.
• Fractures: Bone breaks in the tibia or femur.
• Neurovascular Damage: This is a critical concern, as the popliteal artery (major blood vessel) and peroneal nerve (major nerve) are located behind the knee and are highly susceptible to stretch or tear during dislocation, potentially leading to limb-threatening complications.

Signs and Symptoms

The signs and symptoms of a posterior tibial dislocation are typically severe and immediate:

• Excruciating Pain: Intense pain at the time of injury and thereafter.
• Obvious Deformity: The knee may appear visibly misshapen, with the tibia displaced backward.
• Immediate Swelling: Due to internal bleeding and fluid accumulation.
• Inability to Bear Weight: The knee is unstable and cannot support the body's weight.
• Limited or Absent Range of Motion: Movement of the knee is severely restricted or impossible.
• Neurovascular Compromise: This is a medical emergency. Signs include:
  • Numbness or Tingling: Indicating nerve damage.
  • Coolness or Pallor of the Foot: Suggesting compromised blood flow.
  • Diminished or Absent Pulses: A critical sign of arterial injury requiring immediate attention.

Diagnosis

Diagnosis of a posterior tibial dislocation is typically made rapidly in an emergency setting:

• Clinical Examination: A thorough physical examination will reveal the deformity, instability, and an assessment of neurovascular status (checking pulses, sensation, and motor function in the foot).
• X-rays: Initial plain radiographs are used to confirm the dislocation, identify any associated fractures, and rule out other bone injuries.
• Magnetic Resonance Imaging (MRI): Once the joint is reduced (put back into place), an MRI is crucial for evaluating the extent of soft tissue damage, including ligament tears, meniscal injuries, and cartilage damage.
• CT Angiography: If vascular injury is suspected (e.g., diminished pulses), a CT angiogram may be performed to visualize the blood vessels and assess for tears or blockages in the popliteal artery.

Treatment and Management

Posterior tibial dislocation is a medical emergency requiring immediate attention to prevent long-term complications, especially neurovascular ones.

• Emergency Reduction: The primary goal is to immediately reduce (relocate) the dislocated tibia back into its proper position. This is often done under sedation in an emergency room.
• Neurovascular Reassessment: After reduction, a critical re-assessment of blood flow and nerve function is performed. If vascular injury is confirmed, immediate surgical repair of the blood vessel is paramount to save the limb.
• Surgical Intervention: The vast majority of posterior tibial dislocations require surgical reconstruction due to the extensive ligamentous damage. The timing of surgery may vary, often performed once swelling has subsided and other acute injuries are managed. Surgical procedures may involve:
  • Ligament Reconstruction: Repair or reconstruction of torn PCL, ACL, and collateral ligaments using grafts (autograft from the patient's own body or allograft from a donor).
  • Meniscal Repair/Removal: Addressing torn menisci.
  • Fracture Fixation: If bones are broken.
• Non-Surgical Management: This is exceedingly rare and only considered for extremely stable, isolated posterior PCL injuries without significant associated instability or neurovascular compromise, which is not typical for a true dislocation.

Rehabilitation and Recovery

Recovery from a posterior tibial dislocation and subsequent surgery is a long and challenging process, requiring dedicated physical therapy.

• Immobilization: Initially, the knee may be immobilized in a brace to protect the healing structures.
• Phased Rehabilitation: A structured physical therapy program will progress through several phases:
  • Protection and Pain Management: Focusing on reducing swelling and pain.
  • Restoring Range of Motion: Gradually regaining knee flexion and extension.
  • Strengthening: Building strength in the quadriceps, hamstrings, and calf muscles to support the knee.
  • Proprioception and Balance Training: Re-educating the knee's sense of position and balance.
  • Functional Training: Progressing to sport-specific or activity-specific movements.
• Return to Activity: Full return to high-impact activities or sports can take 9-18 months, depending on the severity of the injury and the success of rehabilitation. Long-term outcomes can vary, with potential for residual instability, stiffness, chronic pain, and an increased risk of developing osteoarthritis in the future.

Prevention

While high-energy trauma is often unpredictable, some measures can help reduce the risk or mitigate the severity of knee injuries:

• Protective Gear: Using appropriate protective gear in sports, such as knee pads, can offer some protection against direct impacts.
• Strengthening and Conditioning: Maintaining strong quadriceps and hamstring muscles can help support the knee joint, although this may not prevent dislocation from extreme forces.
• Awareness: Being aware of the risks associated with certain activities and taking precautions can help.