Osgood-Schlatter disease is an overuse condition that causes swelling and tenderness at the bony prominence (tibial tuberosity) just below the knee. It is among the common sources of knee pain in young athletes and tends to affect children during the growth spurt of their pre-teen or teenage years. The frequency of the condition is not known.

It is named after two physicians, Dr. Robert Osgood and Dr. Carl Schlatter, who defined the disease in 1903. It is also known as osteochondrosis.

Parents and children should not ignore symptoms related to Osgood-Schlatter disease. Trying to play through the pain will likely make the condition even worse. For most children, Osgood-Schlatter disease disappears over a period of between six months to 24 months, although it can take longer and symptoms tend to come and go. Once a child stops growing, the tibial growth plate fuses and patellar tendons strengthen and the pain permanently disappears.

After repeated trauma, new bone grows back during the healing process, causing a permanent, painless bump below the knee. In other cases, a painful bony growth below the kneecap may develop that must be surgically removed. A majority of children with Osgood-Schlatter disease will experience some discomfort as adults while kneeling.

Despite its name, Osgood-Schlatter is less a disease and more of an injury caused by overuse. Experts believe that Osgood-Schlatter disease is a result of contraction of the quadriceps, the large muscles in front of the thigh. These muscles are connected to the patellar tendons that run through the knee and attach to the shin bone (tibia), the big bone in the lower leg. The quadriceps connects to the bone at a fairly small area, and rapidly lengthening bones cause muscles and associated tendons to become tight and inflexible, creating overuse stress on the bone or cartilage in this area and resulting in trauma.

When the quadriceps contract, the patellar tendons pull back from the tibial tuberosity. If this occurs too frequently, it may cause inflammation of the bone, cartilage and/or tendon at the top of the shin bone. The result is pain, which can be intense. In severe cases, the tendon may stretch so much that it detaches from the tibia. When this happens, it may cause the dislodging of a knee bone fragment.

Young athletes are especially prone to Osgood-Schlatter disease, including those who take part in football, soccer, basketball, tennis, figure skating, volleyball, gymnastics and ballet. The reason may be their repative use of quadriceps muscles.

Osgood-Schlatter tends to strike during a child’s growth spurt. Both growth and injury can play a role. The growth spurt is the two-year period when children grow most rapidly. It usually occurs between ages 8 and 13 for girls, and 10 and 15 for boys.

Traditionally, boys have been more likely to be affected by Osgood-Schlatter, but this is changing as girls have become more involved in athletics. The ratio of boys to girls for this disorder is generally 3:2.