The Sacroiliac Joint, otherwise known as the SI joint connects the sacrum (‘Sacro-’), the triangular bone at the base of the lumbar spine just above the coccyx, to the hip bones (‘iliac’). The main function of this joint is to provide shock absorption between the upper body/spine and the pelvis/legs.
These joints typically have very little movement, but the movement they do have helps with the shock absorption and forwards/backward bending. The SI joints are reinforced by very strong ligaments which prevent the sacrum from moving too much. The network of soft tissue surrounding the joint, including the gluteal and piriformis muscles provide support to the joint, as well as assisting in the absorption of pressure and limiting unnecessary joint movement.
It is estimated that the SI joint is responsible for around 15-30% of all lower back pain cases.
Dysfunction of the SI joint can result in lower back pain, pain in the buttock, and/or leg pain. This condition shares some similarities with other diagnoses, such as lumbar disc herniation and piriformis syndrome, which is why it is important to differentiate from these conditions to provide the most effective treatment plan.
There are 3 main mechanisms for SI joint dysfunction including:
- Hypermobility/ instability (too much movement)- this typically causes pain through the lower back/ hip area and may radiate around the front into the groin region.
- Hypomobility (too little movement)- this can cause the muscles to tense up, cause pain, and limits mobility. This can cause pain through one side of the lower back/ buttock and may also radiate into the back of the leg.
- Inflammation/ Sacroiliitis– inflammation of the SI joints can produce pelvic pain and stiffness. Sacroiliitis may be secondary to SI joint dysfunction, or can occur independently with the joint functioning normally- this may then be resultant from an infection, rheumatoid condition etc.
SI dysfunction most commonly affects young and middle-aged women due to the differing pelvis shape from men. The risk also heightens in women who are pregnant or who have recently given birth, due to the laxity of the SI ligaments caused by a hormone to allow the pelvis to stretch for the safe delivery of a baby.
- Lower back pain- typically a dull ache on one side, but can affect both sides.
- Pain can also spread to the buttock, outer hip, outer thigh, and groin.
- Hot, sharp, stabbing pain, or sometimes pins and needles/ numbness into the buttocks or back of the thigh/s (this rarely travels past the knees).
- Stiffness through the lower back, hips, and pelvis.
- Pain may worsen when increasing pressure on the joint affected, I.E. when sitting to standing, walking up/ downstairs, jogging, lying on the side affected.
Conditions SI dysfunction may be confused with:
- Hip bursitis/ tendinopathy
- Piriformis syndrome
- Lumbar facet syndrome
- Lumbar disc herniation/ protrusion
- Lumbar radiculopathy
- Ankylosing Spondylitis
Initially, your therapist will perform a physical assessment of the lumbar spine, pelvis, and hips in order to exclude any of the above conditions and formulate a diagnosis. From here a treatment plan can be devised.
Manual therapy can be used in order to effectively treat an SI dysfunction. The aim of treatment will be to:
- Improve mobility of the surrounding joints, including the hips and lumbar spine to reduce pressure on the SI joints
- Improve mobility of the SI joint if it is hypermobile
- Relax the surrounding muscles
- Balance the pair of SI joints to enhance cohesion
- Ensure the sacrum/pelvis is aligned to improve maximum joint efficiency