There are numerous causes of kneecap pain. The kneecap, or patella, along with the tibia and femur and numerous soft tissue structures, compose the knee joint. The patella protects the anterior or front aspect of the knee joint from injury. However, patella injuries and pain on the anterior aspect of the knee are common, and may be due to the following conditions: chondromalacia patellae, prepatellar bursitis or patellar subluxation or dislocation.
Chondromalacia Patellae
Chondromalacia patellae is a common cause of pain around the kneecap. According to the U.S. National Library of Medicine and the National Institutes of Health, chondromalacia patellae is the softening and degeneration of the articular cartilage on the underside of the patella. Chondromalacia patellae typically occurs in adolescents and young adults, and is believed to be caused by overuse, injury or too much force on the knee. The condition more frequently manifests in girls, although numerous teenagers--including boys--possess patellar misalignments. The NIH states that chondromalacia patellae may be a sign of patella arthritis, which is rare in older individuals. If a person has had a patella dislocation, fracture or other injury, he may have a greater risk for chondromalacia patellae. Common symptoms associated with chondromalacia patellae include the following: knee grinding when the leg is extended or straightened, anterior knee pain that worsens following prolonged sitting or stair climbing and knee tenderness.
Prepatellar Bursitis
Prepatellar bursitis or housemaid's knee syndrome involves swelling and inflammation over the front of the patella. According to the American Academy of Orthopaedic Surgeons, prepatellar bursitis commonly is seen in people who kneel for prolonged periods, such as plumbers, roofers, carpet layers and gardeners. Other populations prone to prepatellar bursitis include athletes competing in contact sports, people who have been in a motor vehicle accident and people with gout or rheumatoid arthritis. The friction on the patella while kneeling irritates the bursa—a small fluid-filled sac—situated just in front of the kneecap. The prepatellar bursa allows the patella to move smoothly under the skin, but if the bursa becomes inflamed, it can fill with fluid and become swollen. Common symptoms associated with prepatellar bursitis include knee pain with activity, rapid swelling on the anterior aspect of the knee cap and a knee cap that's tender and warm to the touch.
Patellar Dislocation
Patellar dislocation, also known as an unstable kneecap, is a painful knee condition caused by a patella that does not track within its trochlear groove on the front of the femur or thigh bone. According to the New England Musculoskeletal Institute, patellar dislocations are a common cause of kneecap pain, especially in younger athletes, and that most of the dislocations occur laterally or toward the outside aspect of the knee. Lateral dislocations of the patella typically cause immediate pain and swelling, and after a dislocation, the patella must be reintroduced into the trochlear groove, although patella relocation may occur spontaneously with knee extension. Other problems associated with lateral patella dislocations include ligament tearing, quadriceps muscle injuries, knee destabilization and the introduction of small cartilage and bone fragments--called loose bodies--from the patella into the knee joint complex.
