This condition is a crack or fracture of the patella, the bone on the front of the knee that covers the knee joint. The patella helps to protect the joint as well as provide strength and stability.
The most common causes of a patella fracture are falls or a sudden, direct blow to the front of the knee. A sudden contraction of the quadriceps muscle in the knee can also cause the bone to crack, preventing the knee from straightening.
The most common symptom of a fractured patella is immediate, intense pain on the front of the knee. Other symptoms include swelling, bruising, lack of mobility in the knee, the feeling of a slight gap on the knee cap, and the inability to straighten the knee.
A fractured patella is usually treated by immobilizing the knee in a cast or brace for several weeks to allow the bone to heal. Surgery is commonly required.