(Jumper’s Knee; Sinding-Larsen-Johansson Syndrome)
Tendons are tough bands of connective tissue that attach each end of a muscle to a bone. Tendinitis is inflammation of a tendon. (See also Overview of Hereditary Connective Tissue Disorders.)
Infrapatellar tendinitis typically affects children aged 10 to 13. It is caused by injury due to physical activities that require jumping and the repetitive use of the knees such as figure skating and basketball or volleyball. The overuse of the knees causes very small tears and inflammation to occur in the tendon under the kneecap (patella).
This disorder causes knee pain and tenderness of the tendon under the kneecap. The pain is worst when straightening the knee while climbing stairs, jumping, or doing knee bends.
The doctor bases the diagnosis of infrapatellar tendinitis on the child's history and a physical examination but may do magnetic resonance imaging (MRI) to view the extent of the injury.
To relieve the pain, children are told to modify their athletic activities, take nonsteroidal anti-inflammatory drugs (NSAIDs), and do physical therapy. Persistent pain may be treated with surgical repair, but this is usually not necessary.