Dislocated Knee

Knee Dislocation Mechanisms
Anterior – severe hyperextension Posterior – AP force to proximal tibia Medial – varus force Lateral – valgus force Rotary – rotary force

Mechanism

high energy trauma (MVA, falls, industrial and athletic injuries)
by definition, caused by tears of multiple ligaments (>3)

Clinical Features

classified by relation of tibia with respect to femur
- anterior, posterior, lateral, medial, rotary
- anterior & posterior >50% of all dislocations
knee instability
effusion, pain

Investigations

x-rays: AP, lateral, skyline
- associated radiographic findings include tibial plateau fracture dislocations, proximal fibular fractures and avulsion of fibular head
angiogram if abnormal vascular exam

Treatment

closed reduction
- complicated by interposed soft tissue
assessment of peroneal nerve and ligamentous injuries
repair of associated injuries
knee immobilization x 6-8 weeks

Complications

high incidence of associated injuries
- popliteal artery tear (especially in anterior and posterior dislocations)
- peroneal nerve injury
- capsular tear
chronic: instability, stiffness, post-traumatic arthritis