Floating Knee - Classifications, Causes, Symptoms, and Management

Introduction:

The term floating knee was coined by Blake and McBryde in the year 1975 to represent the fracture involving the ipsilateral femur and tibia. But, not all fractures fall under a floating knee. The fractures involving both the bones (the femur and tibia) fall under the term floating knee, also known as the flail knee. These fractures are usually complex and have multiple causes which make it appear to be a partial joint or the knee joint appears to be floating. The overall occurrence of the floating knee is uncommon or rare. Although this type of fracture is seen in people performing high-intensity workouts, arduous exercises, or a very active lifestyle, in the case of gender, it has a higher male predilection.

What Is Pathophysiology Behind Floating Knees?

Floating knee injuries involve a mix of fractures occurring in different parts of the knee, including the shaft, the area near the ends of the bones, and within the joint itself. This particular combination of fractures is more frequently observed in adults than in children. However, if the injury extends to the growth plates, known as the epiphyseal region, it can have negative effects on the open growth plates in children. This can lead to issues such as differences in the length of limbs and angular deformities as the child continues to grow.

What Are the Classifications of Floating Knee?

Several classifications have been given to describe this condition, which are given below:

1. Blake and McBryde Classification:

This classification was given based on the site of injury. By this classification, a floating knee can be broadly classified as a type 1 or type 2 fracture.

• Type 1 Fracture: This type of fracture is coined as an original fracture that involves both the bone, namely the tibia, and the femur. Type 1 fracture is the fracture of both shafts.

• Type 2 Fracture: This type of fracture is also called a false fracture as it directly does not involve the bony cortex. This is further classified as Type A and B.

  • Type A affects the knee joint.

  • Type B affects the hip or ankle joint.

2. Classification by Letts and Vincent:

This is a classification given in the system of child medication where it is divided into five categories alphabetically. This includes the following:

• Type A - It is the fracture of two closed primary ossification sites or shaft regions.

• Type B - It is a closed fracture of the neck of the bone (diaphyseal end) and shaft of the bone.

• Type C - It is two closed fractures between the round end portion of the bone (epiphyseal end) and the neck of the bone (diaphysis end).

• Type D - It involves one closed fracture and one open fracture.

• Type E - Here, both fractures are open fractures.

3. Classification by Bohn- Durbin:

• Type 1 - Type 1 fractures are fractures involving the shafts of both the long bones, femur, and tibia.

• Type 2 - The fractures involve only the juxta-articular region of the femur and tibia.

• Type 3 - The fracture involves the epiphyseal component.

4. Classification by Fraser et al:

This classification was given based on knee involvement, where it is broadly classified into types 1 and 2 and then it is further sub-classified into three subtypes.

• Type 1 - Fractures of both bones without involving the knee.

• Type 2 - Fractures involving the knee. Subtype A involves the tibial plateau, subtype B involves the distal femur, and subtype C involves both the tibial plateau and distal femur within the knee joint.

What Are the Causes of a Floating Knee?

Floating knee or the ipsilateral fracture of the tibia and femur is a complex type of fracture that is often involved with higher energy activities, including,

• Road traffic accidents.

• Falling from extreme heights.

• Accidents during walking.

• Accident with cyclists.

• Local trauma to the knee.

• High-impact injuries with a firm dull surface.

• Automobile accidents.

• Athletes.

What Are the Symptoms of a Floating Knee?

• Patients with floating knees have multifold injuries involving both the hard and soft tissue and should not be ignored.

• Patients are usually noticed with increased sensitivity to touch at the site of injury in both the tibial and femoral regions showing a complete changeover in the affected area and also appearing to be shorter than usual.

• Severe soft tissue and vascular injuries and lacerations are seen in this fracture involving a meniscal tear where patients become hemodynamically compromised.

• Patients are presented with severe unbearable pain, swelling, sensitivity, inability to stand or bear weight, and knee instability.

• Delayed complications include infection, increased blood loss, fat embolism, and delayed healing.

How Is a Floating Knee Managed?

The management of this fracture takes various treatment modalities, which can be broadly classified into three main steps:

• Emergency Bone Fixation: This is reducing the fracture and repositioning it, preventing it from further damage.

• Management of Compartment Syndrome: This is a medical condition that occurs due to increased pressure due to excess pooling of blood in a particular region, limiting the blood flow to other places and causing self-strangulation. Hence this is an emergency condition and has to be prevented to maintain proper blood flow to the legs and other regions.

• Management of Life-Threatening Injuries: Other management includes fixing lacerations of the vascular and soft tissue injury.

• The other essential medical management of this fracture is restoring the ABCDE (airway, breathing, circulation, disability, and exposure) and surgical management includes a combination of treatment modalities with plating, nailing, placement of a combination of implants, wiring, and casting.

Over 50 percent of the patients show good to excellent prognosis with proper care and management. Patients with surgical management also show shorter hospitalization times than those with conservative management.

What Does Rehabilitation After a Floating Knee Management Involve?

Following surgical stabilization of fractures, a thorough examination of the knee's range of motion and stability is essential.

1. For cases of collateral ligament laxity, bracing for six weeks is the preferred approach.

2. Reconstruction of injured ligaments is typically postponed until sufficient rehabilitation of skeletal injuries has been achieved.

3. Patients should aim to regain a satisfactory range of knee movement before advancing to other interventions.

4. Adequate pain control in the early postoperative phase, often achieved through methods such as an epidural catheter or systemic opioid infusion, is crucial.

5. Regardless of the fracture pattern, early mobilization of the knee is paramount for achieving optimal outcomes, particularly in intra-articular fractures.

Weight Bearing Restrictions - In Type I fracture patterns, weight bearing is delayed until callus formation is visible on radiographs. For Type II variants, weight bearing is permitted after 10 weeks to prevent articular fragment subsidence.

Beneficial Effects of Early Motion - Extensive literature supports the beneficial effects of early motion on cartilage and periarticular tissue health.

How Is the Floating Knee Diagnosed?

The methods of diagnosis aiding in the management of floating knee fractures include:

• Doppler.

• Magnetic resonance imaging (MRI).

• X-rays.

• Computed tomography (CT) scan.

Doppler and MRI are used to assess soft tissue injuries and to help establish proper blood flow preventing compartment syndrome, fat embolisms, and neurological sensations. CT scans and X-rays aid in determining fractures, the current condition of the patient, and in predicting prognosis.

What Are the Complications of a Floating Knee?

Most of the time, the post-operative complications are lesser. In some cases, the post-operative complications can be life-altering, and they can be:

• Leg length discrepancy.

• Infections leading to knee stiffness.

• Leg amputation.

But complications also seem to be decreased and less complicated when seen involving fractures to the diaphyseal end of the femur or tibia.

Conclusion:

Although a floating knee or ipsilateral fracture of the tibia and femur is said to be uncommon and complicated, it is still treatable. It has a prognosis rate of more than 50 percent globally. With timely diagnosis and well-executed treatment modalities with medical and surgical management, the complications are limited, and excellent outcomes are seen, restoring the patient to a comfortable lifestyle.