How the injured limb compares with the uninjured one, as a percentage.
The Limb Symmetry Index expresses the performance of an injured or operated limb as a percentage of the uninjured limb — for example on strength or single-leg hop tests. A common return-to-sport target is 90% or above, though relying on the uninjured side as the benchmark can flatter results if it has also weakened. It is one of several criteria, not a standalone pass mark.