What is a Supine to Long Sit Test?
The Supine to Long Sit Test, also known as the supine to sit test or long sitting test, is an orthopedic physical assessment for identifying leg length discrepancy and possible dysfunction in the sacroiliac joints. During the test, the patient transitions from a supine (lying down) position to a long sit (sitting up with legs extended) position, allowing the examiner to observe any changes in leg length. This test helps differentiate between functional and structural leg length discrepancies.
However, it is important to note that the Supine to Long Sit Test has poor validity and reliability. Levangie in 1999 published research about several clinical tests (the standing flexion test, the Supine to Long Sit Test, the Seated Forward Flexion Test, and the Gillet Test. The research showed that the Supine to Long Sit Test and cannot consistently produce accurate or reliable results, making it less effective for clinical use. This research also showed that combining tests did not increase performance characteristics either. Research by Bemis and Daniel (1987) further supported this, reporting that the long sitting test has negative predictive values.
Despite these limitations, it can still be utilized as a screening tool to identify potential issues before conducting more definitive assessments.
How is this test conducted?
Here's how to do the test:
- Have the patient lie in a supine position.
- Place the patient in a hook lying position by bending their knees and placing their feet flat on the table.
- Ask the patient to perform a bridge by lifting their hips off the table and then returning to the starting position to reset pelvic alignment.
- Instruct the patient to extend their legs fully.
- Hold the patient's legs with your thumbs on the medial malleoli and observe for any discrepancies.
- Ask the patient to sit up into a long sit position while you continue to monitor leg length.
To more easily see how the test is conducted, consult our template. It contains images for the main positions assumed in the test.
How are the results interpreted?
A negative result indicates no discernible leg length discrepancy during the transition from supine to long sit position, suggesting that there is no significant functional leg length discrepancy or sacroiliac joint dysfunction.
A positive test is observed if there is a noticeable leg length discrepancy during the movement. This discrepancy suggests potential sacroiliac joint dysfunction or functional leg length discrepancy, where the apparent leg length changes due to pelvic or muscular imbalances rather than actual differences in bone length.
