- The sacroiliac joint (SI joint) is the junction formed by the Ilium and the sacrum with ligaments that allow for little movement within the joint. The joint is classified as synovial so it is susceptible to a number of injuries and disorders such as sprain, inflammation, hyper-mobility, hypo-mobility, all of which can ultimately lead to low back pain.
- Anterior sacroiliac ligament
- Interosseus Sacroiliac
- Posterior (Dorsal) Sacroiliac ligament
- Sacrotuberous ligament
- Sacrospinous ligament
Synovial Joint anatomy
- All synovial joints are composed with two or more articulating bones
- Both of the bones are lined with a thin, smooth articular cartilage
- Surrounded by a joint capsule
- Synovial membrane that produces synovial fluid which acts as lubrication, shock absorption, and carries nutritional values for the joint.
- Main support comes from ligamentous structures.
Common disorder that occurs at the SI joint
SI Joint dysfunction
- What is SI joint dysfunction?
- Damage to ligamentous structures that make up the sacroiliac joint. Often times this causes the joint to be hypo-mobile which can lead to inflammation of the affected area.
- Common mechanism
- Excessive twisting
- Bending forwards with knees locked out
- Repetitive unilateral activities that increases the load of the opposite SI joint.
- Signs and Symptoms
- Palpable pain and tenderness directly over the joint with associated muscle guarding.
- Pain can often radiate into the thigh and sometimes into the groin area.
- Unilateral activities such as single leg squats, single led raises (especially after 45 degrees)reproduce pain.
- leg length discrepency (whether at the ASIS/PSIS or malleolar level) which can be caused by rotation of the pelvis.
- Side bending toward affected side could also reproduce pain
- Treatment techniques
- Use of modalities such as Heat (Prior to exercises), ice (post exercises) to manage pain.
- Movement of the joint to correct alignment. Techniques such as Muscle Energy are useful in restoring proper alignment of the pelvis.
- In the event that the SI joint is hyper-mobile due to the sprain then strengthening exercises should be incorporated to improve stability.
(Prentice, W. 2006)