The SI Joint
The SI joint (formally known as the Sacro-Iliac joint) is the junction between the sacrum (the base of your spine) and the ilium (think “hands on your hips” bone). It is a location commonly found to be painful or often described as a cause for spinal limitations. Forces tend to be high in this region due to the weight of our upper half compressing down through the base of our spine. There are times when the SI joint can experience higher than tolerable pressures or tension and that can result in symptoms many of us have known at some point or another. The typical explanatory power for those symptoms is a bit lacking in the current paradigms and may be due for an update. The approach of creating more stability via strength work could be an oversimplification, nuances exist that might influence outcomes.
The complexity of the SI joint is extensive, and no model completely describes it, but there are deeper levels of understanding that do not often get relayed to patients or the general public. This joint is very compressed to begin with, in fact many older individuals develop a form of biological fusion at this joint. This may mean that it is prepared to, and often does, handle high forces. If compression reaches a certain threshold, which is different for every individual, pain or discomfort can arise. This could be due to environmental influences or genetics. Two muscular aspects of anatomy that are rarely described as complicit in the development of SI joint pain is the gluteus maximus and the latissimus dorsi with their associated connective tissues. These muscles have direct attachments on the joint and if overutilized may be contributors to the development of symptoms. Exercises targeting glutes and lats often influence how the SI joint moves or doesn’t move. They tend to be trained with the intention of increasing strength, which is useful at times, however they also transmit forces directly to the affected SI joint in this circumstance. Training them has a place, however also training them to reduce their output when desired may limit compression at the SI joint and allow for greater mobility.
The SI joint is built to withstand heavy loads and does not tend to have a great degree of mobility right out of the gate. It can be a source of pain or immobility in the right circumstances and the way we approach our training programs influences these symptoms. Choosing the right exercises and clarifying our intentions on what we want from muscles in the area may be an invaluable part of managing SI joint issues.
Austin Ulrich, Physical Therapist
