Assessing the SI joint: the Thigh Thrust Test

Several studies conclude the odds of the SI joint being directly involved in cLBP is from 5-15%; its contribution in acute pain is nebulous. Orthopedic tests create an odds ratio of about 75% for SI involvement if several (4 of 5) of the assessment tests are positive. Conversely if 4 of 5 are negative an equal odds ratio exists. Recently a few studies now suggest the thigh thrust and sacral compression may be the most pertinent. Mcgill also describes an oscillation/rebound test created by the vertical fist placed under the sacral base being rapidly closed…thus creating a ‘bounce’ and a mild irritation to the structures.

The thigh thrust is designed as an SI assessment. The supine patients’ thigh and knee are bent to 90 degrees and the testers hand is positioned on the sacral base. A vertical transmission of force through the thigh via the clinicians body stresses the joint and tissues. Pain in the SI is a positive test. The torsion effect puts stress on the soft tissue structures of the SI. It is possible that reproduction of symptoms for the patient in areas commonly referred to by the SI joint may also indicate a positive result. The Thigh Thrust has shown specificity of up to 92% in 3 systematic reviews and sensitivity of 80-96%.