There is some controversy amongst various branches of the health profession about the relevance of the Sacroiliac joint in lower back pain – Chiropractors consider it to be a major cause of lower back pain, although many other branches of the health professions do not, because none of the body’s muscles are capable of creating movement at this joint, and its movements are very small and difficult to assess. Please refer also to Sacroiliac Joints and Yoga.
However that may be, the Sacroiliac joint is supported by very strong ligaments which are connected to the spinal muscles, Gluteus Maximus and Biceps Femoris. These muscles all play a role in stabilising the joint and tension in the ligaments has been linked to lower back pain. The Piriformis attaches to the Sacrum and if there is a difference between the strength of the left and right sides, a twisting force is applied to the Sacrum, causing misalignment and pain.
A pain-free alignment of the Sacroiliac joint depends on a balance between all of the many muscles attached to the hipbones. If you only strengthen your legs, and in particular the hamstrings, and don’t pay much attention to the stabiliser muscles of the hips and abdominal wall, Sacroiliac problems are inevitable.
Ellenbecker, De Carlo, DeRosa, 2009, Effective Functional Progressions in Sport Rehabilitation
De Franca, 1996, Pelvic Locomotor Dysfunction
Franklin, 2004, Conditioning for Dance