MANUAL MINORS
Patellar dislocation occurs when the patella shifts out of its normal position in the femoral groove, usually towards the lateral side of the knee. This dislocation can be traumatic (caused by a direct blow or sudden twisting of the knee) or recurrent, associated with predisposing anatomical factors such as femoropatellar dysplasia or ligament laxity.
Patellar dislocations are more common in adolescents and young adults, particularly in women, and may be associated with soft tissue injuries around the knee, such as damage to the medial patellofemoral ligament (MPFL).
Diagnosis
The diagnosis is based on a history of traumatic event or sudden knee movement, followed by intense pain and visible deformity at the front of the knee, with the patella displaced laterally. The patient often struggles or is unable to extend the knee.
In most cases, the patella spontaneously returns to its normal position (spontaneous reduction).
Confirmation is made via anteroposterior and lateral X-rays to verify the patella’s position and rule out fractures. In cases of recurrent dislocation or ligament damage, magnetic resonance imaging (MRI) can be useful to evaluate soft tissue injuries, including the medial patellofemoral ligament or articular cartilage.
Differential Diagnosis
Condition | Key Differentiation |
|---|---|
Patellar Fracture | Knee pain without lateral displacement of the patella; visible on X-rays. |
Knee Dislocation | Displacement of the tibia and femur out of alignment, with extensive ligament damage. |
Anterior Cruciate Ligament (ACL) Injury | Instability without visible patellar displacement; Lachman’s test positive. |
Patellar Tendon Injury | Inability to extend the knee without patellar displacement. |
Chondromalacia Patella | Anterior knee pain without history of acute trauma or visible displacement. |
Emergency Management
Initial management of a patellar dislocation in the emergency setting includes:
Closed Reduction: If the patella has not returned to its normal position spontaneously, a closed reduction should be performed. This is typically done with the patient in a supine position, applying gentle pressure on the displaced patella while extending the knee. Successful reduction is confirmed by pain relief and restored range of motion.
Immobilisation: After reduction, a knee splint or immobiliser is applied to maintain stability. The knee is kept in full extension for 2-3 weeks.
Analgesia: NSAIDs or opioids are administered for acute pain management.
Evaluation of Associated Injuries: If there is significant effusion, persistent instability, or suspicion of fractures, additional MRI or X-rays may be requested.
Definitive Treatment
Definitive treatment depends on the severity of associated damage and the recurrence of the dislocation:
Conservative Treatment
For isolated, uncomplicated dislocations, conservative treatment is usually sufficient. This includes using a knee brace or immobiliser to keep the knee extended for 2-3 weeks. Physiotherapy is initiated after this period to restore range of motion, strengthen the quadriceps, and stabilise the knee.
Rehabilitation: Strengthening the quadriceps muscle (especially the vastus medialis) is key to preventing recurrence. Patients should avoid high-impact activities and twisting movements of the knee during recovery.
Surgical Treatment
In cases of recurrent dislocation or significant ligament or osteochondral injuries, surgery may be necessary. Options include:
Repair or Reconstruction of the Medial Patellofemoral Ligament (MPFL): This ligament is repaired or reconstructed to prevent recurrent patellar instability.
Realignment Surgery: In cases of significant misalignment or femoropatellar dysplasia, osteotomy may be needed to correct alignment.
Osteochondral Fracture Repair: If the dislocation caused a fracture in the articular cartilage, this may require arthroscopic fixation or repair.
Rehabilitation
Rehabilitation is critical following patellar dislocation, whether treated conservatively or surgically. Physiotherapy is recommended to improve range of motion and strengthen the quadriceps, helping stabilise the patella and prevent future dislocations.
Depending on the severity of the injury, full recovery may take 4 to 6 months. Preventing recurrence is crucial and can be achieved through strengthening exercises and modifying physical activities that pose a risk of knee twisting or instability.
Long-term follow-up is important to monitor patellar stability and prevent complications such as chondromalacia patella or patellofemoral osteoarthritis.
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