The "one finger test" for sacroiliac (SI) joint pain is more formally known as the Fortin finger test. It's considered positive, suggesting SI joint dysfunction, if the patient consistently points to a specific, painful spot within 1 centimeter of the posterior superior iliac spine (PSIS) on two separate occasions.
Here's a breakdown:
-
Purpose: The Fortin finger test aims to identify whether the patient's pain source is likely the SI joint. It leverages the idea that pain stemming from the SI joint is often localized.
-
Procedure:
- The patient is asked to point with one finger to where they feel their most intense pain.
- The location is noted relative to the PSIS (a bony prominence easily felt on the lower back).
- This process is repeated on a separate occasion (e.g., later in the same appointment or at a subsequent visit).
-
Positive Result: The test is considered positive if:
- The patient points to the same area on both occasions.
- That area is within a 1 cm radius of the PSIS.
-
Significance: A positive Fortin finger test strongly suggests SI joint dysfunction as a possible cause of the patient's lower back pain. However, it's essential to remember that this is just one piece of the diagnostic puzzle.
-
Important Considerations:
- The Fortin finger test is not definitive. It should be used in conjunction with other physical examination findings and, if necessary, imaging studies to confirm the diagnosis.
- It's crucial that the patient truly identifies the most intense pain, as referred pain can sometimes cloud the picture.
- Variations exist in how strictly the 1cm rule is interpreted in clinical practice.
In summary, the Fortin finger test is a valuable tool for assessing SI joint pain. A positive test indicates a high likelihood of SI joint involvement, particularly when considered alongside other clinical findings.
