What does a positive 90-90 test indicate?

A positive 90-90 test indicates shortened distal hamstring length. This test is performed with the patient lying supine, and the examiner flexes the hip to 90 degrees while observing the knee position. If the knee cannot achieve full extension and remains flexed, this suggests that the distal hamstrings (the semitendinosus, semimembranosus, and biceps femoris muscles at the knee) are tight or shorten.

In clinical practice, this finding is significant as it may contribute to functional limitations, such as issues with sports performance, gait deviations, or lower extremity mechanics. Therefore, identifying a positive result on the 90-90 test allows the clinician to assess hamstring tightness and consider appropriate treatment or rehabilitation strategies to address these limitations.

In contrast, results indicating normal distal hamstring length would show that the knee can be fully extended during the test. Similarly, normal proximal hamstring length would not be assessed by this particular test. Additionally, instability of the knee joint is not assessed through this test, as it specifically evaluates the flexibility of the distal hamstrings rather than joint stability.