Several conditions such as Osgood-Schlatter Disease, and Sever's Disease, are types of growing pains. These conditions are caused by inflammation around sites where large tendons insert. These tendons pull on the growing bone (at the growth plate) and cause inflammation.
Growing pains are almost always seen in active youths, often while participating in sports. Growing pains are best treated with rest, stretching, and ice packs. If activities are causing significant growing pains, they should be avoided until the symptoms resolve.