Osgood-Schlatter disease. Coloured X-rays of the knees of a 15-year-old patient comparing the normal appearance of the right knee with that of the left knee, which is affected by anterior tibial apophysitis (Osgood-Schlatter disease). Osgood-Schlatter disease (OSD) is inflammation of the patellar ligament at the tibial tuberosity that is characterised by a painful bump just below the knee that is worse with activity and better with rest. Here, diagnosis was based on the combination of swelling and blurring of the patellar tendon contours at its insertion, oedema (swelling) of the neighbouring soft tissues and irregularities of the ossification nucleus.