MANUAL MINORS
Knee dislocation is a severe injury where the bones of the knee joint (femur and tibia) are completely displaced from their normal alignment. This is an orthopaedic emergency due to the high risk of vascular injury, particularly to the popliteal artery, and nerve damage. Knee dislocations typically occur due to high-energy trauma, such as car accidents or falls from heights, but they can also result from low-energy trauma in individuals with weak or lax ligaments.
Diagnosis
A patient with a knee dislocation presents with severe pain, visible joint deformity, significant swelling, and an inability to move or bear weight on the affected leg. Given the severity of this injury, distal pulses and limb perfusion must be assessed immediately to rule out vascular damage.
X-rays confirm the dislocation, while an arteriogram or Doppler ultrasound is necessary to evaluate potential vascular injuries. MRI or CT scans are helpful for assessing ligament damage and associated bony injuries.
Differential Diagnosis
Condition | Key Differentiation |
|---|---|
Supracondylar Fracture of the Femur | Knee deformity with visible fracture on X-rays, without complete loss of joint alignment. |
Patellar Dislocation | Lateral displacement of the patella without loss of congruence between the femur and tibia. |
Cruciate Ligament Injury | Instability without complete displacement of the knee bones. |
Tibial Plateau Fracture | Fracture of the proximal tibia, without displacement of the tibia relative to the femur. |
Meniscal Injury | Pain with joint locking, but no deformity or visible dislocation on imaging. |
Emergency Management
Knee dislocation requires urgent treatment, including:
Immediate Closed Reduction: This should be performed as soon as possible, ideally under sedation or anaesthesia. Traction and realignment are applied to restore joint congruence. Early reduction minimises the risk of permanent damage to vessels and nerves.
Vascular Evaluation: Due to the high incidence of popliteal artery injury, distal pulses (posterior tibial artery and dorsalis pedis artery) must be assessed. If pulses are absent or signs of ischemia are present, an arteriogram or Doppler ultrasound is required to evaluate vascular injuries. Emergency vascular surgery may be necessary if vascular damage is confirmed.
Immobilisation: After reduction, the knee is temporarily immobilised with a splint or long leg cast until ligamentous and vascular structures are fully evaluated.
Analgesia: NSAIDs or opioids are administered for acute pain control.
Definitive Treatment
Definitive treatment depends on the degree of injury to the ligaments, cartilage, vessels, and nerves. Surgery is required in most cases:
Ligament Repair or Reconstruction: Knee dislocations are usually associated with severe tears of the cruciate ligaments (anterior and posterior) and collateral ligaments (medial and lateral). Surgical repair or reconstruction is often necessary, which may be performed in one or multiple stages.
Vascular Repair: If popliteal artery damage is confirmed, urgent vascular repair is required to restore blood flow to the leg and prevent tissue necrosis or amputation.
Fracture Management: In cases of associated fractures, open reduction and internal fixation (ORIF) with plates or screws are performed, depending on the fracture type.
Rehabilitation
Rehabilitation is a lengthy process and is essential for functional recovery of the knee. It includes:
Early Immobilisation: After reduction and necessary surgeries, the knee may be immobilised for several weeks to allow initial tissue healing.
Progressive Physiotherapy: As tissues heal, passive range-of-motion exercises are initiated to prevent joint stiffness. Gradually, muscle strengthening and stability exercises are introduced.
Functional Rehabilitation: Over time, physiotherapy focuses on improving knee stability, strength, and function, which can take several months.
Recovery from a knee dislocation can take 6 months to over a year, depending on the severity of the injury. Long-term complications, such as post-traumatic osteoarthritis or chronic knee instability, may require continuous monitoring.
Complications
Complications associated with knee dislocation include:
Vascular Injury: Damage to the popliteal artery can lead to ischemia, which may result in amputation if not treated promptly.
Nerve Injury: The common peroneal nerve, which runs near the knee, may be damaged, leading to weakness or paralysis of the foot (“foot drop”).
Post-Traumatic Osteoarthritis: Extensive ligament and cartilage damage may cause joint degeneration over time, leading to chronic pain and stiffness.
Joint Stiffness: Prolonged immobilisation or excessive scar tissue formation may limit the knee’s range of motion.
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