What is ADHD? ADHD (attention deficit-hyperactivity disorder) affects both adults and school-aged children. Symptoms include restlessness, difficulty paying attention, and hyperactivity. The causes of ADHD are unknown, however factors such as diet, environment and genetics may contribute to symptoms.
The knee muscles control how the knee joint and patella move. There are two main groups of muscles, the quadriceps and the hamstrings, as well as a small muscle behind the knee (popliteus).
The patellar tendon is the structure lying below the kneecap (patella) attaching the quadriceps muscle to the tibia. Through the patellar tendon the quadriceps contraction allows the knee to extend or straighten.