Described as painful lump below the kneecap, Osgood-Schlatter disease (OSD) is an overuse injury (read: not a disease, which is why some refer to it as Osgood-Schlatter syndrome) affecting the knee. It’s the inflammation of the cartilage, bones, and/or tendons in the area of the knee where the kneecap connects to the top of the shinbone. OSD occurs in pubescent children, most frequently those who participate in sports. This most likely is because growth spurts involve the rapid and nonsynchronous growth of muscles, bones, and tendons. Exercise adds stress during this vulnerable period, especially to the growth plate at the top of the shin. Symptoms of OSD include pain that worsens during exercise and improves during periods of rest; swelling or tenderness (or a lump) under the knee; limping, and muscle tightness. OSD typically goes away on its own, following puberty and/or the growth spurt (i.e., once the bones stop growing). Until then, medical professionals recommend simply treating the symptoms, which predominantly involves rest—a tough prescription to abide by when it comes to active children. Physical therapy can play a key role in managing OSD. In addition to recommending footwear, including shock-absorbent insoles, and appropriate sports pads, therapists can teach children stretching and strengthening exercises to help the knee.