Shear wave elastography for assessing lower extremity muscle stiffness after anterior cruciate ligament reconstruction: A systematic review.

In 30 seconds

This systematic review synthesized studies using shear wave elastography (SWE) to assess lower-extremity muscle stiffness after anterior cruciate ligament reconstruction (ACLR), comparing reconstructed limbs with contralateral limbs or controls. Six studies included 173 people after ACLR and 79 controls; study quality ranged from poor to good. Passive vastus medialis stiffness was consistently lower in operative limbs than in controls (Hedges’ g -1.10 to -1.21) and was associated with strength, knee function, and landing biomechanics. Semitendinosus stiffness was also reduced after hamstring tendon harvest, although findings varied by muscle region and assessment timing.

Key findings

• Passive vastus medialis shear modulus was lower in operative limbs than controls (g -1.10 to -1.21).
• Reduced semitendinosus stiffness after hamstring tendon harvest was reported (g -1.29 to -1.64), but not at the mid-belly after return to sport.
• Vastus medialis stiffness was associated with quadriceps strength, knee function, and landing biomechanics.
• Longitudinal stiffness deficits persisted at three months, while findings during active contraction conflicted.

Why it matters

The review suggests that muscle mechanical properties after ACLR may provide information not captured by strength benchmarks alone. In particular, lower passive vastus medialis stiffness was linked to functional and landing measures, while semitendinosus changes may reflect hamstring donor-site effects. These findings support further study of muscle-specific assessment, but do not establish that SWE-guided decisions improve outcomes.

What to keep in mind

Only six studies were included, with quality ranging from poor to good. Active-contraction findings conflicted, and no study sampled the distal vastus medialis obliquus or distal hamstring musculotendinous region.