Patellar Dislocation

Aka: Patellar Dislocation, Patellar Subluxation

1. Epidemiology
   1. More common in teenage girls and young women
      1. Associated with increased Q-Angle (see below)
2. Mechanism
   1. Forceful deceleration with concurrent knee rotation or
   2. Valgus force with strong quadriceps contraction
      1. Results in lateral Patella displacement out of groove
3. Predisposing factors
   1. Miserable Malalignment Syndrome
   2. Tight lateral Retinaculum
   3. Patella Alta
   4. Patella hypermobility
   5. Vastus lateralis hypertrophy
4. Symptoms
   1. Anterior knee ripping or tearing sensation at injury
   2. Knee flexes with dislocation
   3. Patella relocates with knee extension
   4. Subluxation associated with giving way sensation
5. Signs
   1. Knee held in semi-flexed position
   2. Dislocation
      1. Concurrent osteochondral Fracture in 28-52% patients
      2. Associated with Anterior Cruciate Ligament Tear
   3. Subluxation
      1. Instability and weakness
      2. Reluctant to bear weight
   4. Predisposing factors
      1. Examine for predisposing factors listed above
      2. J-Sign
      3. Quadriceps angle (Q-Angle) >15 degrees
6. Radiology: Knee XRay
   1. Views
      1. Merchant and Infrapatellar views (knee flex 45)
      2. Anteroposterior, Notch, and lateral views
   2. Interpretation
      1. Often normal
      2. Medial Patella avulsion Fracture
      3. Osteochondral Fracture
7. Management
   1. Patella reduction (if still dislocated)
      1. Gentle knee extension and
      2. Gentle lateral Patella pressure
   2. Bracing and taping
   3. Alter aggravating activity
   4. Physical Therapy and Rehabilitation
      1. Soft tissue and Patellar mobilization
      2. Muscle Strength
         1. Vastus medialis oblique
         2. Gluteus
         3. Foot and ankle
   5. Consider immobilization
      1. Indications
         1. First Patella dislocation and
         2. No significant Vastus Medialis disruption
      2. Technique
         1. Immobilize for 6 weeks
         2. Knee in full extension
         3. Foam pad protects Vastus Medialis
         4. Lateral support holds Patella medially
   6. Maintenance
      1. Patellar stability program after rehabilitation
   7. Surgery Indications
      1. Inadequate improvement in 6 months
      2. Osteochondral Fracture