Floating Knee

As early as 1975, the term floating knee was used by Blake and McBryde to describe fractures of the ipsilateral femur and tibia. Fractures can occur anywhere along the femur and the tibia and must occur in both bones to be considered a floating knee injury. Floating knee refers to the knee joint and not necessarily the connection to either long bone. Although tibial and femur fractures are not uncommon, having injuries to both bones simultaneously on the ipsilateral limb is uncommon. Floating knee injuries are usually complex, with various mechanisms of injury and often complicated treatments.

Also known as "flail knee," floating knee injuries have been classified using various systems:

Blake and McBryde Classifications

These are based on the site of the injury.

1. Type I: Fractures of both shafts of the 2 long bones

2. Type II-A: Involves the knee joint

3. Type II-B: Requires involvement of the hip or ankle joints

Letts-Vincent Classifications

This is a pediatric classification system that first classifies the region of the fracture and whether it is an open or closed fracture.

1. Type A: Two closed diaphyseal fractures

2. Type B: Two closed fractures, with one being diaphyseal and the other metaphyseal

3. Type C: Two closed fractures, with one being diaphyseal and the other epiphyseal

4. Type D: At least one open fracture

5. Type E: Both fractures are open

Bohn-Durbin Classifications

Like the Letts-Vincent classification, this is a pediatric classification system that first classifies the region of the fracture and whether it is an open or closed fracture.

1. Type I: Double shaft fractures

2. Type II: Injuries are juxta-articular

3. Type III: Injuries have an epiphyseal component

Fraser et al. Classifications

1. Type I: Shaft fractures of both bones without the involvement of either fracture into the knee

2. Type II: Fractures extended into the knee and were further subdivided

   1. Type IIa: Involved the tibial plateau

   2. Type IIb: Included the distal femur into the knee, and

3. Type IIc: Involved both the tibial plateau and the distal femur within the knee joint