The sitting active and prone passive lag test: a validity study in a symptomatic knee population.

Only 27 participants and 54 knees were tested, so the findings may not generalise beyond this small group. There was no gold standard or reference standard for knee extension lag; the test was judged against the symptomatic versus asymptomatic side. Only people with one symptomatic knee and a normal other knee were included, so it does not address bilateral knee problems or acute conditions. The normal side was used as the reference, but a normal knee may not present with exactly 0 degrees of extension. The test did not identify the exact structure responsible, and tightness of the iliopsoas was ignored. Maintaining the required sitting posture and ankle position may be difficult or missed, which could make results inaccurate. The test was performed in open kinetic chain positions, and the paper says translation to closed kinetic chain function is not fully justified. The study did not show that treatment based on the test improves symptoms or function.

The authors reported no funding and no conflict of interest.

Do not treat a positive SAPLT as proof of a specific tissue problem or as evidence that treatment will improve knee extension. The study had no gold standard, only 27 participants, and five asymptomatic knees tested positive.