B: Radiculopathy of the sciatic nerve
Diagnose sciatica in a pregnant patient.
This patient most likely has radiculopathy of the sciatic nerve (Option B), commonly known as sciatica. One quarter to one third of patients experience some hip pain during pregnancy; the most common causes are sciatica, sacroiliitis, and round ligament pain. Hip pain in pregnancy is caused by a combination of factors, including an enlarging uterus, which increases the mechanical load to the hip joints, and loosening or laxity of the ligaments of the sacroiliac joints due to relaxin and estrogens, which contribute to joint hypermobility and widening of the symphysis pubis, which in turn alters the pelvic architecture. Sciatic nerve compression in the lumbosacral spine leads to pain, tingling, and numbness that radiate into the leg.
Hip osteoarthritis (Option A) causes pain that begins in the hip joint and radiates to the groin, not the buttocks. Range of motion is usually limited, and even passive range of motion can reproduce pain. This patient's normal range of motion and positive straight leg raise test make hip osteoarthritis unlikely.
Round ligament pain (Option C) is a common cause of hip pain during pregnancy, especially in the second trimester. It is characterized by sharp pains in the abdomen, hip, and groin area, intensifying with rapid movements or changes in position. The pain does not radiate, and the straight leg raise test is normal in patients with round ligament pain.
Sacroiliitis (Option D), or inflammation of the sacroiliac joints, may occur as an isolated musculoskeletal condition or as part of a spondyloarthritis. Pregnancy, leg length discrepancies, scoliosis, and lumbar fixation increase risk for sacroiliitis. On physical examination, there is pain with palpation of the sacroiliac joint; however, passive range of motion is unaffected, and straight and contralateral leg raise tests produce no pain. The diagnosis of sacroiliitis is more likely with a positive FABER test, in which pain is reproduced when the hip is Flexed, ABducted, and Externally Rotated.
Sciatica is characterized by sciatic nerve compression in the lumbosacral spine, leading to pain, tingling, and numbness that radiate into the leg.
Kesikburun S, Güzelküçük Ü, Fidan U, et al. Musculoskeletal pain and symptoms in pregnancy: a descriptive study. Ther Adv Musculoskelet Dis. 2018;10:229-34. [PMID: 30515249] doi:10.1177/1759720X18812449