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).
Common Causes of Behind-Knee Pain The most likely cause is biceps femoris tendinitis, or inflammation of a hamstring tendon where it connects to the back of the knee. This can lead to pain when you bend the knee against resistance, or stiffness in the morning or after exercise.