The patella is commonly referred to as the kneecap. It is a thick, circular-triangular bone located in front of the knee joint — where the thighbone (femur) and shinbone (tibia) meet. It is a small freestanding bone that rests between the femur and tibia. The patella is coated with cartilage on its undersurface and is important in providing strength of extension (straightening) of the knee joint. It protects the knee and connects the muscles in the front of the thigh to the tibia. In addition to most motions that require movement of the leg, the kneecap plays a vital role in how the knee bends.
Patellar fractures account for about 1% of all fractures. They are most common in people who are 20 to 50 years old. Men are twice as likely as women to fracture the kneecap.
Causes of Patella Fracture
A patella fracture is usually caused by a forceful direct blow to the knee, such as the knee contacting the dashboard of a car in an accident or direct trauma from an opponent during sport. The patella fracture may consist of a single crack across the kneecap, or the kneecap may be broken into several pieces, in what is known as a ‘stellate’ fracture. In some instances, a forceful contraction of the quadriceps muscles can be enough to cause a fracture of the patella. This causes a horizontal crack across the kneecap, which makes it impossible for the patient to straighten their knee.
If the patella or the tendon associated with it becomes injured, a person will experience difficulty walking, running, standing or engaging in athletic activity. If dislocated, the kneecap can no longer slide along the thigh bone’s grooves, which can aggravate and damage cartilage on both the femur and the tibia. Dislocation and other traumatic injuries are common among athletes and other people who are extremely physically active. Injuries tend to be more pronounced in high impact sports. For example, patella-related injuries are common in sports like football, mixed martial arts and wrestling. The patellar fractures are serious injuries and often require surgery to heal. Over the long term, they may cause arthritis in the knee.
Symptoms
The major symptoms of a patellar fracture include:
- Severe pain in and around the kneecap
- Swelling
- Inability to straighten the knee
- Difficulty extending the leg or doing a straight-leg raise
- A deformed appearance of the knee due to the fractured pieces
- Tenderness when pressing on the kneecap
- Bruising
- Inability to walk
Patella Fracture Treatment
Patella fractures should be seen in the emergency room. X-rays will determine the type of fracture and the amount of displacement (separation) of the fracture. One of the critical factors in determining treatment is a thorough examination. Specifically, doctors will check to see if the patient can perform a straight leg raise. A straight leg raise test is done by having the patient lie flat.