Obviously, Jimmy may limp as a result of a limb injury. If the limp is severe, especially if there is swelling, you should go to the doctor for X-rays. But limping can also occur with no evident injury. One common cause in toddlers is a condition called toxic synovitis. In this case, Jimmy would wake up one day and refuse to put weight on his foot despite the fact that there is no obvious swelling on the leg and that he feels no pain if you press anywhere on it. Toxic synovitis may sound frightening, but it’s simply a temporary inflammation of the hip joint that frequently follows a cold or another viral illness. There is usually no fever, and it disappears quickly. The next day or so, Jimmy will walk normally again. If the pain persists, or if fever and swelling occur in any leg joint, take him to the doctor.