When the knee joint is isolated partially or completely due to fracture of the femur and tibia the term "Floating Knee" is used . Survivors of high-speed traffic accidents often have injuries to several of the parenchymal organs as well as multiple fractures. Careful evaluation of these injuries and resuscitation of the patient must precede the definitive management of specific fractures.
Hayes JT  suggested that automobile passengers with floating knee, braced their feet firmly against the sloping floor of the front seat just prior to the collision, their legs getting crumpled under the massive decelerating forces produced by the impact. Pedestrians were frequently catapulted some distance from the point of impact and were further injured by striking the pavement. In a study of 222 cases of floating knee by Fraser , all cases were involved in road traffic accidents.
Studies showed associated injuries like head injuries, chest injuries, abdominal injuries and injuries to other extremities. Most of the injuries to the head, chest and abdomen were life threatening. Adamson et al in their study encountered 71% major associated injuries with 21% vascular injuries . The reported mortality rate ranged from 5% – 15%, reflecting the seriousness of the associated injuries . Deliberate and careful examination of the patient must be carried out in order to determine whether a major intracranial, abdominal or thoracic injury is present. Such injuries should take precedence over extremity injuries in the priority of treatment.
There are plenty of studies in the literature detailing different management options for the Floating Knee. Hayes JT  opined that in a patient with multiple fractures in the same extremity, operative fixation of one or more of the fractures was valuable in the management of the entire limb. Ratcliff AH  found that internal fixation of both the fractures should be done wherever possible as these patients were less likely to develop knee stiffness or shortening and were in hospital and off work for less time than those treated conservatively. Omer GE  treated the Floating Knee by both conservative and operative fixation found that where internal fixation was done for both femoral and tibial fractures, the healing time was about 8 weeks earlier than the group managed conservatively. Behr JT  treated patients with the Floating knee by closed intramedullary nailing with Ender nails and achieved femoral union at an average of 10.3 weeks and tibial union at 18 weeks. Ostrum RF  treated patients with a retrograde femoral tibial intramedullary nail through a 4 cm medial parapatellar incision. The average time to union of the femoral fractures was 14.7 weeks and that for the tibial fractures was 23 weeks. They opined that this method was an excellent treatment option.
The general consensus in recent studies is that the best management for the Floating knee is surgical fixation of both the fractures with intramedullary nails. Dwyer used combined modalities of treatment with one fracture managed conservatively and the other surgically. They concluded that the treatment method for the tibia did not interfere with joint mobilisation . Lundy recommended surgical stabilisation of the fractures for early mobilisation which produced the best results . Theodoratus recommended intramedullary nailing as the best choice of treatment except for grade 3B & C open fractures . Single incision technique for nailing of both the fractures have been recommended by several authors [7, 16, 17]. Rios J compared single incision versus traditional antegrade nailing of the fractures and found the former to have less surgical & anaesthesia time with reduced blood loss . Shiedts found an increased incidence of fat embolism when both fractures were treated by reamed nails .
Szalay  demonstrated knee ligament laxity in 53% of patients while 18% complained of instability. Most of the patients with instability had a rupture of the anterior cruciate ligament with or without damage to other ligaments. They concluded that knee ligament injury was more common with floating knee injuries than with isolated femoral fractures and advocated careful assessment of the knee in all cases of fractures of the femur and floating knee injuries. Other studies  have showed that the incidence of knee ligament injuries in the floating knee was upto 50%, most of which were missed in the initial assessment. Meticulous examination of the knee at the time of injury is strongly advocated although the practicality of this method is questionable.
Our study showed a male predominance comparable to other studies. Most of the studies showed road traffic accidents as the only mode of injury. In our study, the most common mode of injury was road traffic accidents but two of our patients sustained their injury after a fall from height. This mode of injury for the Floating Knee has not been mentioned in the literature reviewed. The classification used by us was the one that was proposed by Robert Blake . This was used as it took into account the injuries sustained at the hip or ankle of the affected side and helps one in planning the surgical procedure. The other classification system advocated by Fraser  includes intra-articular fractures at the knee but does not mention about injuries to the ipsilateral hip or ankle both of which can have implications on the surgical management of the Floating Knee. Our management consisted of treating both the femoral and tibial fractures surgically, most of them by intramedullary nailing using an interlocking nail. With this management, we found the fracture union time and functional recovery was better than the other surgical modalities. This was in accordance to studies by Gregory  and Ostrum RF  who had excellent results with fixation of both fractures by intra-medullary nailing. Both these authors used a retrograde nailing for the femur although in our study all the nailing was antegrade. Though no knee problems have been found when single incision technique is used [4, 7, 16] we feel that antegrade nailing allowed easier knee ligament reconstruction if needed as the femoral nail inserted retrograde would make knee ligament reconstruction technically difficult.
Intra-articular involvement of the fractures, higher skeletal injury scores and severity of soft tissue injuries are significant indicators of poor outcome results [21–23]. Hee suggested a preoperative scoring system which took into consideration the age, smoking status at time of injury, Injury severity scores, open fractures, segmental fractures and comminution to prognosticate the final outcome of these fractures .
The best results were seen when both fractures were treated by intramedullary nailing. We found that these patients returned to their normal level of activity earlier than when the fractures were treated with other modalities. Tibia fractures treated with external fixation had a longer union time probably related to the soft tissue injury and comminution at the initial injury. The 3 patients who had a poor outcome in our study were 2 patients with tibia plateau fractures who had knee stiffness and persisting pain in the knee while the other patient had a Grade 3B open tibia fracture treated by external fixation. This shows that the poor prognostic factors were related to the type of fracture (open or closed, intra-articular fractures, severe comminution). The associated injuries played a major role in the initial outcome of patients in our study with regards to delay in initial surgery, prolonged duration of surgery, anaesthetic exposure and delay in rehabilitation. From our study we found Floating knee injuries to be a group of complex injuries that needed careful assessment to detect poor prognostic factors (open, intra-articular, comminuted fractures) and associated injuries, surgical fixation of the fractures with thorough planning of surgeries and prolonged rehabilitation. Combination of all these would determine the ultimate outcome of these patients.