Osgood–Schlatter disease is painful swelling of the bony prominence of the shin (called the tibial tuberosity) just below the knee. It occurs most commonly in teenagers who play a lot of sports and is thought to be caused by excessive, repetitive pulling of the quadriceps muscle at the front of the thigh, which is transmitted to the tibial tuberosity.
The pain is usually worse during physical activity and eases with rest. Usually, only one leg is affected.
Treatment is not usually needed, apart from rest and pain relievers, and the condition typically clears up within a few weeks or months.