The patella (knee cap) is a bone found in front of the knee joint. Its function is to protect the knee and improves the function of the quadriceps muscles in the front of the thigh.
As the knee bends and extends, the patella glides over the surface of the femur (thigh bone). The under surface of the patella is covered by smooth articular cartilage to all easy movement.
Cause of fracture:
- Direct trauma: Due to its position under the skin in front of the knee, it is vulnerable to fracture with direct trauma e.g. falling directly on the knee or being hit by a car. The resulting fracture may be a single simple fracture dividing the patella into two parts, or it can have multiple fracture lines (comminuted fracture) breaking the bone into multiple pieces.
- Indirect trauma: this is due to sudden violent contraction of the quadriceps (thigh muscle) pulling the patella apart. This can occur, for example, during a fall from height when the patient tries to extend the knee against the force of the body weight.
- The patient is usually unable to extend the knee fully against resistance and is unable to walk.
- Bruising and swelling occurs on the front of the knee.
- The x-ray is usually enough to confirm the diagnosis and determine the fracture pattern.
If the fractured pieces are not displaced away from each other, the fracture can be treated without surgery, by putting the leg in a cast or a splint until the fracture unites.
However, in the majority of cases, the fragments are displaced from each other, thus hindering union of the fracture. In this case the treatment is surgical by fixing the fractured fragments using screws or wires. Sometime there are multiple small fragments that cannot be fixed. In this case, these small fragments may be removed (partial pattelectomy).
Following surgery, it is important to start movement of the knee as early as possible to avoid formation of adhesions and stiffness of the knee joint and to strengthen the muscle around the knee.