The sacroiliac joint (SI joint) is the joint between the sacrum (lower spine) and illium (pelvic bone). This joint moves every time we take a step. Sometimes this joint becomes stuck or locked causing low back pain. The surrounding muscles of the SI joint often go into spasm as a protective mechanism. Pain is experienced in the buttock and thigh regions. It is typically aggravated by sitting for long periods. Various athletic activities, including walking, running, jumping, leaping, and squatting, can produce unwanted motion or stress in the SI joint and surrounding tissues. Soft-tissue failure, overload injuries, weak core stabilizing muscles, stress and direct traumas can all contribute to this condition. SI joint pain may also be a distant manifestation of an injury in other parts of the kinetic chain that are stressed during sports activities.