SI Joint Syndrome

• Strong joints held by numerous ligaments (anterior, posterior, interosseous, sacrotuberous, sacrospinous SI ligaments) and it supports weight of entire upper body
• Combination of a synovial plane joint and a fibrocartilage joint (sacral surface has hyaline cartilage, while iliac surface has fibrocartilage)
• ROM of SI joints is only 4 deg of rotation and up to 1.6 mm of translation
• Dislocations are very rare due to the ligaments and interlocking of the bones, thus pelvic fractures are more common than tears of the interosseous ligament
• Functions include shock absorption, force transmission from lower limbs to spine and vice versa, provides stability during push off phase of walking1

INNERVATION

• Many authors have reported innervation of the SI joints by lower lumbar and upper sacral PPRs, although the exact levels are not agreed upon or may be variable from person to person1
• Other studies have also shown that some nerve fibers innervating the SI joint and surrounding ligaments are small and contain substance P, which could explain nociception from the area when inflamed1

CLINICAL Background

• SI pain represents 15-30% of individuals with mechanical non-radicular low back pain2,3
• Predisposing factors include trauma, pregnancy, certain athletes, leg length discrepancies, older age, inflammatory arthritis & previous spine surgery3,4
• It can result from an aberration in the movement of the SI joint(s) (either too much or too little), repetitive trauma or inflammatory conditions such as AS, psoriatic arthritis, Reiter’s arthritis, etc.5

Signs/symptoms

• Instability from trauma or ligament laxity (pregnancy) can lead to repetitive trauma and inflammation
• A leg-length discrepancy as small as 1 cm increases the load across the SIJ fivefold1
• Patient may point towards the PSIS of affected side (Fortin finger test)
• Usually unilateral dull pain and/or stiffness, but may become sharp during certain activities such
• Pain can occasionally refer down to hip, buttocks, groin or posterior thigh (but not below knee​
• Aggravated by sitting for long periods of time, standing from a seated position, going up stairs, rolling from side to side in bed, flexing while standing, or getting in and out of a vehicle
• Relieved by laying down​

TREATMENT

• Manual therapy  SI joint adjustments or mobilizations, soft tissue therapy to surrounding musculature and/or ligaments5,6
• Education about posture and ergonomics6
• Lumbopelvic stability exercises5,6
• Intra-articular steroid injections5,6
• Anti-inflammatory medication4
• Pelvic belts4
• Surgical fusion (last resort after failure of conservative measures)