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What is Sacroiliac Joint (SI Joint) Dysfunction?

What is Sacroiliac Joint (SI Joint) Dysfunction?

January 9, 2021

The sacroiliac (SI) joints are the joints between the sacrum and each ilium (hip bone). The sacrum is the wedge-shaped bone that sits at the base of the lower back and the ilium is one of the three bones that make up the pelvis. The ilium is the bone you feel when you “put your hands on your hips.” The two dimples in the lower back are located directly over the SI joints.

The SI joints are viewed as the foundation for every other joint in the body as a result of their relationship with the spine and the legs. Strong ligaments connect the pelvis to the spine and stabilize the SI joints. One of the main functions of the SI joints is to transmit force from the legs to the spine. As the ligaments that stabilize the SI joints are very strong, there is a limited amount of movement in the SI joints, but that small amount is very important for normal spine and hip mobility. People can develop SI joint pain if the joints move too much (hypermobility) or too little (hypomobility). If the SI joints do not move normally, they can affect the mobility of every joint in the legs and the spine due to the body’s attempts to compensate for the abnormal SI joint mobility. It is common for SI joint dysfunction to be the root cause of many lower extremity problems, including ITB syndrome, Achilles tendinitis, patellofemoral pain (knee pain), and hip bursitis. SI joint dysfunction can also cause neck, mid-back, and lower back pain, as well as headaches. If the SI joint dysfunction is severe and also affects the mid-back or neck, it can also affect the mobility of the upper extremities.

What Causes SI Joint Dysfunction?

One of the most common causes of hypermobility is pregnancy. The ligaments that stabilize the SI joints and pelvis stretch during pregnancy to allow a woman’s pelvis to widen. This causes both increased movement at the SI joints as well as potential inflammation of the SI joints due to the increased movement and increased weight from pregnancy. Many women experience lower back pain during and after pregnancy. Often, SI joint dysfunction is a contributing factor to their symptoms.

Trauma is another common cause of SI joint dysfunction. A fall onto the buttocks or any other impact to the pelvis can injure the ligaments of the SI joints. Head injury can also affect the SI joints due to the transmission of force down the spine to the pelvis. The sacrum often gets stuck in a descended (towards the feet) position, which severely affects both spinal mobility and hip mobility.

Having poor posture, muscle imbalances, sleeping funny, or sitting funny can affect the SI joint. If you spend a lot of time in a dysfunctional posture or position, the SI joint on one side can get stuck not moving, and the one on the other side can start to move too much. This asymmetry causes pain and dysfunction elsewhere in the body as you compensate for the altered movement.

Leg length discrepancy can also cause SI joint problems. Unequal leg length puts asymmetrical stress on the SI joints and spine, causing inflammation and hypermobility. There are two types of leg length discrepancies: true and functional. A true leg length discrepancy occurs when the bones of the right leg are a different length than the bones of the left leg. Some people develop a leg length discrepancy as a child (due to a fracture in the growth plate) or later in life as a result of improperly healed fracture or surgery. True leg length discrepancy is also a risk after a total hip replacement. Functional leg length discrepancies occur not as a result of different length bones, but due to soft tissue or postural dysfunction.

A person who has to wear an immobilization boot due to an ankle or foot injury will have a functional leg length difference unless they wear a shoe with similar sole height on the non-injured leg. It is common for a patient who was in a boot (and did not wear a shoe of similar sole height) to develop SI joint dysfunction and lower back pain. Another cause of functional leg length discrepancy is limited joint or muscle mobility. For example, if someone hurt their knee (or had knee surgery) and it was painful to keep the knee straight, the person might sleep and sit with their knee bent most of the time to avoid pain. Over time, the muscles and connective tissue in the knee will stiffen, and the result could be that the person does not stand or walk with their knee fully straight. This would cause a functionally shorter leg.

SI joint dysfunction and pain can be caused by arthritis. The SI joints contain cartilage and synovial fluid just like other joints in the body. Arthritis causes the cartilage to wear and become inflamed and affects the quality of the synovial fluid. People with an inflammatory condition called ankylosing spondylitis often first develop pain and stiffness in the SI joints.

The physical therapists at Carlson Therapy Network are well known for their expertise in evaluating and treating SI joint dysfunction. We use a whole-body approach to determine the root cause of our patients’ problems. We are highly skilled manual therapists who use gentle techniques to address SI joint dysfunction, decrease pain, and help our patients get back to the activities they love.

Contact Carlson ProCare today to make an appointment with a Physical Therapist to assess your SI Joint.


  • Fu, Kai-Ming. (2018 March.) Sacroiliac Joint Dysfunction. Weill Cornell Brain and Spine Center.
  • Chang, Lewis, MD. (2021 April.) Weill Cornell Brain and Spine Center. Sacroiliac Joint Dysfunction. <>
  • Giammatteo, T. and Weiselfish Giammatteo, S. (2003.) Integrative Manual Therapy for Biomechanics: Application of Muscle Energy and “Beyond” Technique. North Atlantic Books.

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