The Single Leg Squat Test: A "Top-Down" or "Bottom-Up" Functional Performance Test?
Lindsay A Carroll, Benjamin R Kivlan, RobRoy L Martin and 2 others
PMID 33842032WHAT IT FOUND
Healthy adults who failed the single leg squat for knee collapse had the same ankle movement and foot posture as those who passed.
A restricted ankle or flat foot does not explain poor single leg squat performance in this group.
Key findings
01There were no significant differences in ankle dorsiflexion range of motion or foot posture between subjects who passed versus failed the single leg squat for medial knee deviation.
02The study refutes the possibility of a bottom-up approach to explaining increased medial knee deviation during the single leg squat in healthy individuals.
03Clinicians should not use the clinical single leg squat protocol to detect differences in the clinical characteristics of the foot and ankle.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only young, healthy, active adults (mean age 25.2 years), so the results may not apply to older adults or people with existing musculoskeletal dysfunction. The sample was 77% female, which may limit generalizability. The single leg squat protocol used did not require a specific squat depth (like 60 degrees of knee flexion), so participants may not have reached end-range ankle dorsiflexion where restrictions might become apparent. Goniometry has a measurement error of 6-8 degrees, which is large relative to the available ankle range of motion, potentially masking small differences. Foot posture was measured statically with the Foot Posture Index, which may not reflect dynamic foot function during the squat.
Declared interests
The authors declare that there is no conflict of interest.
The easy way to misread this
Do not interpret this null finding as proof that ankle restrictions never cause knee valgus. The study used a common clinical single leg squat protocol that did not force participants into deep squats. If you squat a patient to 60 degrees of knee flexion or deeper, you might still see ankle restrictions contribute to poor mechanics.