Lower limb kinematics of single-leg squat performance in patients with anterior cruciate ligament deficiency.
Shigeki Yokoyama, Wataru Fukuda, Yutaro Ikeno and 2 others
PMID 34083883WHAT IT FOUND
In patients with an ACL-deficient knee, the injured leg showed less knee valgus during a single-leg squat than the uninjured leg.
This counterintuitive finding suggests patients may subconsciously avoid the valgus position to protect the unstable knee.
Key findings
01The maximum knee valgus angle was significantly smaller for the injured leg (9.7°) than for the uninjured leg (15.2°).
02At the point of maximum squat depth, the knee valgus angle was significantly smaller for the injured leg (7.3°) than for the uninjured leg (13.0°).
03There was no statistically significant difference in maximum knee flexion between the injured and uninjured legs, although a trend for decreased flexion in the injured leg was observed.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The sample size was very small (15 patients), limiting the generalizability of the findings. The study did not measure muscular strength or balance ability, which are known to influence single-leg squat performance and may have contributed to the observed kinematic differences. Gender-related differences in joint movement were not analyzed due to the small sample size, despite previous literature suggesting such differences exist. Participants had a wide range of time since injury (mean 85 days, SD 52.6), meaning the stage of tissue healing and rehabilitation varied considerably.
Declared interests
None declared.
The easy way to misread this
Do not interpret the lower valgus angle on the injured side as evidence of better movement control. The authors suggest this is likely a compensatory strategy to reduce mechanical load on the unstable knee, meaning the injured limb is moving differently to protect itself, not because it is stronger or more stable.