PATELLA INSTABILITY

17 Oct PATELLA INSTABILITY

Pathophysiology

• Mechanism
  • non contact twisting injury to extended and externally rotated. Osteochonral fracture happens while patellar relocation.
  • Direct blow due to collision on the side of knee

Anatomy

• Static stabilizers
  • MPFL ( Medial patella femoral ligament)
  • Patellar boney confirmity
• Dynamic stabilizer
  • vastus medialis

Epidemiology

• Risk factors
  • Marfans syndrome
  • Ehlers-Danlos syndrome
  • external tibial torsion
  • Femoral antiversion increased
  • Genu valgum
  • Increased Q angle
  • patella alta
  • Trochlear dysplasia
  • Lateral femoral condylar hypoplasia
  • Excessive lateral patellar tilt
  • Dysplastic vastus medialis obliques
  • Tight lateral structure(ITB, Vastus lateralis)

Classification

• Acute more due to direct injury
• Chronic recurrent dislocation
• Habitual occurs whenever patient bends his knee

Clinical features

• Symptoms and signs
  • Anterior knee pain
  • Instability
• Examination
  • knee effusion in acute case due to haemarthrosis
  • Tenderness over MPFL
  • Increased lateral translation of patella more than 2 quadrants
  • Patellar Apprehension sign positive
  • Increased Q angle
  • J sign

Imaging

• X- ray
  • antero posterior
  • lateral view
  • merchants view
• CT scan
  • TT-TG distance > 20mm abnormal
• MRI
  • MPFL tear

Treatment (Adult)

• Pain killers, physiotherapy, activity modification and bracing
  • 1st time dislocation without bony avulsion or osteochondral fracture
• Operative
  • Arthroscopic debridement or repair
  • MPFL repair with or without graft
  • Lateral reticular or ITB release
  • Fulkerson osteotomy
  • Distalization of tibial tubercle
  • Trochleoplasty

Complication

• Recurrent dislocation
• Patella femoral arthritis
• medial patellar dislocation