Toddler is always complaining that his legs or his hands are hurting. what could cause this?

Need more info: If the symptom of pain is associated with refusal to use the limbs, swelling, redness or fever, it would be important to get evaluation by your doctor. Many kids wake up at night with leg pains, but are very active with running and jumping during the day and have normal findings. Possible diagnosis includes arthritis, Sickle cell, injury, Charcot Marie Tooth, sensitivity syndromes, and acrodynia