Sacro-iliac joint pain (sacroiliitis)

  • Buttock or PSIS (posterior superior iliac spine) pain (occas. rad. to hamstrings)
  • Often reported triggered by trauma or pregnancy
  • Pain worse after immobility or trunk rotation
  • Ask about inflammatory symptoms (IDB or Reiter's synd.)
  • Beware septic / constitutional symptoms
  • Morning stiffness eased by exercise suggest inflammatory cause

Examination

  • Pelvic tilt with lumbar scoliosis (apparent leg length discrepancy)
  • Pain on SIJ compression (press on S2 process and PSIS)
  • Point tenderness over sacral sulcus (dimple of PSIS)
  • Normal neurology
  • Provocation tests variable prediction:
    • Lateral pressure on ASIS (press down, patient lying on their side)
    • FABER test (make a "4" with legs, flex, abd, ext rotate)
    • Gaenslen test (flex hip, good leg over side trolley into extension, rotates SIJ and pain)

Differential Dx

  • Ank. Spond.
  • NOF#
  • Iliotibial Band Syndrome (or less commonly snapping hip - pain more lateral)
  • Lumbar radiculopathy (NB neurology)
  • Piriformis syndrome (local tenderness behind neck of femur)
  • Other arthropathy (incl. septic, psoriatic)
  • Sup Cluneal Nerve synd. (trigger point just above iliac crest)
  • Trochanteric bursitis (local trigger, FABER positive)

Investigations

  • FBC, ESR, CRP, ANA
  • Consider (GP to request) HLA B27, Rheumatoid factor, PSA, Urine electrophoresis
  • Imaging:
    • Plain films of little use
    • CT = spurring, sclerosis or sublux. of the SIJ
    • Bone scan hot (both?) SIJ in inflammatory e.g. Ank. Spond.
    • MRI useful, particularly of differential Dx (e.g. AVN femoral head) unclear

Management

  • Rest and Ice therapy if early symptoms
  • NSAIDs
  • Refer physio (US therapy, myofascial stretching etc) but warn patient may transiently exacerbate symptoms
  • Refer rheumatology if suspicion underlying inflammatory process