The kneecap (the patella) is a triangular bone at the front of the knee. Several tendons and ligaments connect to the kneecap, including ones attached to the upper leg (femur) and lower leg (tibia) bones.
Though the kneecap is not needed for walking or bending your leg, it makes your muscles more efficient and absorbs much of the stress between the upper and lower portions of the leg. Climbing stairs and squatting can put up to seven times your normal body weight on the kneecap and the joint behind it.
The kneecap can fracture in many ways: partially or completely or into only a few or into many pieces. Sometimes when the kneecap is fractured, the ligaments or tendons attached to it can be sprained or torn.
Symptoms may include:
- Severe pain in and around the kneecap
- Swelling
- Pain when moving the knee in both directions
- 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
In most cases, a broken kneecap is caused by a direct blow to the front of the knee from a car accident, sports or a fall onto concrete.
Kneecap fractures account for about 1% of all skeletal injuries. Most kneecap fractures are suffered by people between the ages of 20 and 50.
A doctor can often diagnose a fractured kneecap by asking you about the details of your accident and examining you. Your doctor will look at your knee, focusing on where it is tender, swollen or misshapen. Your doctor will also ask you to raise your leg or extend your knee, possibly after giving you a local anesthetic to eliminate pain. This helps him or her see if there are other injuries in and around your knee.
X-rays, taken from several angles, are the best way to find out the extent of a fractured kneecap and to check for other injuries. If other injuries are suspected, a computer tomography (CT) or magnetic resonance imaging (MRI) scan may be done.
Two types of surgery may be done to repair a fractured kneecap:
- Open reduction-internal fixation (ORIF) surgery. The surgeon opens the skin and puts the broken bones back together with metal wires, pins or screws. Broken pieces of bone too small to be fixed are removed. If the kneecap is so severely fractured that it cannot be repaired, it may be partially or totally removed.
After the bones have been joined, the opening is closed, a sterile dressing is put over the area and the knee is put in a cast or other device so it cannot move while it heals.
Sometimes, especially in patients who are thin, the wires, pins or screws can be irritating. If so, the devices will be removed after your kneecap has fully healed. - Full or partial patellectomy. This two-hour procedure removes all or part of the kneecap. If your surgeon finds that the break is too severe to repair, he or she will remove the damaged pieces of bone.
The surgery preserves the quadriceps tendon above the kneecap, the patellar tendon below and other soft tissues around the kneecap. After this surgery, you will be able to extend your knee, but the strength of the extension will be weaker.
Once your kneecap has healed, making the muscles around your knee stronger can help avoid further injury. Playing contact sports or doing other activities that put stress on your knee can increase the risk of having another injury to the kneecap. You should avoid these activities or use a kneepad to cushion the blow when playing contact sports. Physical therapy, learning ways to spare your knee stress and strengthening and conditioning your leg muscles on an on-going basis can help prevent more injuries to the knee. Your best exercise options are low-impact and non-weight-bearing, like stationary bikes and certain weightlifting programs, so that the knees do not have to absorb shock.
