Elicitation of a past history of uveitis or the existence of family members with features of spondyloarthropathies also strongly suggests the disease. In patients whose sacroiliac radiographs are normal, the presence of HLA-B27 is highly suggestive but not definitive evidence of the disease. Juvenile-onset ankylosing spondylitis typically presents as peripheral oligoarthritis, often with enthesopathy and infrequently with spinal symptoms. Spinal involvement usually appears later in young adulthood. Physical Examination Examination of the back may be relatively normal early in disease.
Sacroiliac joints are usually painful when palpated or stressed.
When the disease advances into the lumbar spine, the normal lordotic curvature may be lost and paravertebral muscle spasm is prominent. Forward bending, or flexion, may be restricted as measured by the Schober test. In this measurement, two points are drawn with the patient standing erect, one at the L5-S1 region and the other 10 cm above this region. With normal flexion, the distance between these two points increases by 4 to 6 cm, but when the lumbar spine becomes fused, there may be little or no increase in distance between the two points. Lateral lumbar bending and extension are also typically restricted.