The distal femur is the lower end of the thighbone that lies just above the knee joint and resembles an inverted funnel. The end of the bone is lined by a thick, slippery substance called cartilage, which allows it to glide across other bones that form the joint. It also assists in the movement of the distal femur when the knee bends. A crack or break in this part of the bone is medically referred to as a distal femur fracture of the knee. If the force causing the fracture is strong enough, it may also damage the kneecap.
Such fractures are commonly seen in people over age 50 because their bones are relatively weaker. However, younger individuals are also at risk, though the causes may differ.
Your Guide to Distal Femur Fractures
Types of Distal Femur Fractures
- Closed Fracture – The skin is not ruptured.
- Open Fracture – The skin is cut open during the injury, and a part of the bone may protrude.
- Comminuted Fracture – The bone shatters into multiple pieces; these are considered complex fractures.
- Transverse Fracture – The crack or break runs straight across the bone.
These fractures may not only damage the femur but also affect the tendons and ligaments that surround it. The hamstring and quadriceps muscles may shorten or tighten when the bone breaks.
Fractures of the distal femur can involve the articular component, joint surface, or cartilage surface. They may be classified as intra-articular fractures, intercondylar femur fractures, supracondylar fractures, distal femoral fractures, or coronal plane fractures that extend into the knee joint. The lateral femoral condyle, medial and lateral compartments, and proximal tibia may also be involved.
Causes
- Fall from a height
- Vehicular accident, especially motor vehicle accidents involving high-energy trauma
- Loss of bone strength and density with age
- Direct impact to the knee
- Sports injuries
- High-energy trauma
Symptoms
- Severe pain
- Inability to stand or bear weight
- Swelling
- Tenderness over the injured area
- Visible deformity
- Change in gait, as the leg may appear crooked or shorter
Diagnosis
- Clinical evaluation of the injured leg by an orthopedic specialist, including assessment of the distal thigh and femoral region
- Review of the mode of injury, medical history, and symptoms
- Testing the blood supply and nerve function; assessment for vascular injury, especially to the popliteal artery, is crucial
- X-rays, CT scans, or MRI may be used to evaluate the fracture site, fracture pattern, and joint involvement
Treatment
- If the bone is stable and the fracture is not complex, a cast or plaster may be sufficient.
- A traction pin and pulley system may be used for skeletal traction and limb stabilization before surgery.
- Surgery may be required for open fractures to prevent infection. External fixation devices (screws and pins attached to an external frame) may be used.
- Internal fixation with metal plates, screws, or rods can stabilize the femur. Options include plate fixation, distal femur fracture fixation, and less invasive stabilization systems (LISS). Distal locking screws stabilize the bone and maintain alignment, while care must be taken to prevent irritation or injury to soft tissues.
- Severely damaged bone may require a bone graft, often taken from the pelvis, or use of artificial bone fillers or allografts.
- Knee replacement surgery may be recommended for elderly patients or severe fractures.
- Weight-bearing status is determined by fracture stability and healing progress.
- A knee brace may be used during rehabilitation to support the joint.
- Deep vein thrombosis (DVT) prophylaxis is important to prevent blood clots after surgery.
- Physical therapy is essential after surgery to restore flexibility, strength, and function. Early movement helps prevent stiffness and promote recovery.
Management of elderly patients may require a multidisciplinary approach.
Anatomy of the Distal Femur
The distal femur, located at the lower end of the thighbone above the knee joint, plays a vital role in movement and weight-bearing. It forms the upper part of the knee joint and supports activities like walking, running, and standing.
At its core are the femoral condyles—two rounded prominences known as the lateral and medial condyles. These articulate with the tibia and kneecap, creating smooth surfaces necessary for knee movement. Between them lies the intercondylar notch, a groove that serves as the attachment site for the posterior cruciate ligament (PCL) and other stabilizing structures of the knee joint.
Above the condyles is the supracondylar region, which is particularly prone to fractures, especially in younger patients and children. Because of its complex structure and attachment points, fractures in this area vary in pattern and severity.
Surrounding the distal femur are strong muscles and connective tissues. The quadriceps muscles at the front of the thigh help straighten the knee, while the hamstrings at the back help bend it. Ligaments and tendons, including the posterior cruciate ligament, add stability and maintain proper joint alignment.
Understanding the anatomy of the distal femur is essential for diagnosing and treating fractures. The specific location and type of fracture guide treatment, which may include internal fixation, external fixation, or minimally invasive options like percutaneous fixation.
After surgical treatment, physical therapy is key to regaining strength, flexibility, and range of motion. Because of the complexity of the distal femur, careful rehabilitation is necessary to ensure proper healing and safe return to activity.
