Knee Fractures and Dislocations

Fractures of the knee include fractures of the patella, femoral condyles, tibial eminence, tibial tuberosity and tibial plateau. Fractures of the knee can result in neurovascular compromise or compartment syndrome. Soft-tissue infection or osteomyelitis may occur with open fractures. Other complications include non-union, delayed union, osteoarthritis, avascular necrosis, fat embolism, and thrombophlebitis.

Knee dislocation is a relatively rare injury but may be associated with serious vascular injury and often presents with multisystem trauma or spontaneous relocation, making diagnosis difficult.

• May follow a direct blow to the patella, sudden forceful knee flexion or contraction of the quadriceps muscle.
• Presents with pain, swelling, crepitus and difficulty with extending the knee.
• Displaced, transverse fractures result in an inability to straight leg raise, which can also be caused by rupture of quadriceps tendon or patellar tendon.
• May result in an associated haemarthrosis.
• X-rays: may be difficult to interpret because the patella overlies the distal femur and subtle fractures may be obscured. In a bipartite patella, the accessory bone is usually in the upper, lateral part of the patella.

Initial management

• Vertical fractures: analgesia, immobilise in a non-weight-bearing cylinder POP, provide crutches and arrange orthopaedic follow-up.
• Transverse fractures: tend to displace due to the pull of quadriceps. Provide analgesia and immobilise in a POP backslab but refer to the orthopaedic team for probable open reduction and internal fixation.

• The patella usually dislocates laterally.
• Most common in adolescents and more common in girls.
• Usually caused by a twisting injury or a direct blow, with the knee in slight flexion.
• There may be an associated osteochondral fracture.
• The dislocation may reduce spontaneously and there may be a history of recurrent dislocation.
• Presents with knee pain and the knee is held in flexion with lateral displacement of the patella.
• X-rays: usually not required prior to reduction of the dislocation.
• Reduction can be achieved using Entonox. Standing on the lateral side of the limb. the affected knee is held gently and the patella levered medially, smoothly but firmly, with both thumbs. It is helpful for an assistant to gently extend the knee as the dislocation is reduced. Successful reduction rapidly relieves symptoms.
• Once reduced, provide adequate analgesia, arrange x-rays, immobilise in cylinder cast POP (canvas back-splint for recurrent dislocation) and arrange orthopaedic follow-up.

Recurrent dislocation

• Becomes easier with each episode of dislocation and is often bilateral.
• Conservative treatment: reduce the dislocation and apply a plaster backslab, followed by quadriceps strengthening exercises.
• The tendency to dislocation may resolve without further intervention but surgery may be required if persistent despite conservative management.

• Tenderness is usually greatest over the medial aspect of the upper patella.
• A POP or splint may be used for severe pain and tenderness; otherwise refer to physiotherapy and arrange orthopaedic follow-up.

• Rare and indicates severe disruption of the cruciate and collateral ligaments and other soft tissues of the knee.
• There may be fractures of the tibial spine or the tip of the fibula due to ligament avulsion.
• There may also be an injury to the popliteal artery and nerve (distal pulses and sensation should be checked and monitored). Popliteal artery damage may not be initially evident but develop some hours later.
• Reduction requires IV opioid analgesia and sedation and is by traction and correcting the deformity.
• Check distal artery and nerve function after reduction. The apply a long leg POP backslab and arrange admission.

• Falls onto an extended leg can cause compression fractures of the proximal tibia.
• Valgus stresses, e.g. pedestrians involved in RTAs, crush or fracture the lateral tibial plateau.
• Varus injuries result in crushing or fracture of the medial tibial plateau and are usually associated with rupture of the collateral ligaments.
• Present with tenderness over the medial or lateral margins of the proximal tibia, swelling, haemarthrosis and ligament instability.
• X-rays changes may be subtle: breaks in the articular surfaces of the proximal tibia, avulsions from the ligament attachments or loss of height from the medial and lateral tibial plateaux.
• Treatment: adequate analgesia, long leg POP backslab and referral to the orthopaedic team.
• Often require elevation; sometimes requires open reduction and internal fixation with bone grafting.
• Small, isolated avulsions without haemarthrosis may be treated with analgesia, immobilisation, crutches and orthopaedic follow-up.
• Possible complications include knee joint deformity, joint stiffness and osteoarthritis.