Figure. Anteroposterior radiograph of the pelvis.
A 66-year-old man presents with a 6-month history of pain in the left side of his lower back that radiates to his buttock and left groin. He reports that the pain does not radiate down the leg and hip motion does not induce additional pain. Physical examination of the left hip does not reveal pain with hip flexion and internal rotation. The patient has a negative straight leg raise and motor function is intact in the left lower extremity. He has tenderness to palpation over the inferior medial aspect of the posterior superior iliac spine. He also has pain with flexion abduction and external rotation of the hip. Anteroposterior radiograph of the pelvis is obtained (Figure).
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The patient is most likely presenting with sacroiliac (SI) joint arthritis. SI pain may originate from a number of factors including arthritis, ligamentous inflammation, spondyloarthropathies, and infection.1
SI pain is often an overlooked diagnosis that may be the cause of chronic lower back pain in up to 30% of patients with the condition.2 SI pathology may also cause 40% of new-onset back pain after lumbar fusion.2 Diagnosis of SI pain requires a thorough history and close attention to physical examination findings. Patients will often point directly over the SI joint in the region inferior medial to the posterior superior iliac spine, which is considered a positive Fortin finger test.
Pain localized over the SI joint with flexion abduction and external rotation of the hip (FABER or Patrick test) is an additional provocative test. Groin pain with a Patrick test may indicate a hip joint or hip flexor tendon source of pain. An SI joint compression test performed with the patient in a lateral position may reproduce symptoms.
Sacroiliitis is commonly seen in teenage to middle-aged males with a history of ankylosing spondylitis or Reiter syndrome, which is distinctly different from SI joint arthritis.3 Piriformis syndrome often presents with pain when sitting for >20 minutes, buttock pain with internal rotation of the hip, and tenderness to palpation over the posterior greater trochanter. A sacral insufficiency fracture should be considered in the differential diagnosis in patients with SI joint pain, a history of osteoporosis, and normal radiograph results.1-3
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.
1. Forsthoefel C. Sacroiliac pain and dysfunction. OrthoBullets website. https://www.orthobullets.com/spine/422812/sacroiliac-pain-and-dysfunction. Updated February 29, 2020. Accessed March 30, 2020.
2. Dengler J, Kools D, Pflugmacher R, et al. Randomized trial of sacroiliac joint arthrodesis compared with conservative management for chronic low back pain attributed to the sacroiliac joint. J Bone Joint Surg. 2019;101(5):400-411.
3. Krueger C. Sacroiliitis. OrthoBullets website. https://www.orthobullets.com/spine/2040/sacroiliitis. Updated January 4, 2020. Accessed March 30, 2020.