Elastography of the Achilles Tendon: Normal and Tendinopathy Stiffness
Shear wave elastography (SWE) is used for the quantitative assessment of Achilles tendon stiffness. In SWE, push pulses are sent to the tissues, inducing shear waves that are tracked by diagnostic images; color maps are expressed in quantitative units — m/s or kilopascals (kPa) (Diagnostic Ultrasound: Musculoskeletal, Griffith, 2025).
Normal and Tendinosis: Provided Values
According to Diagnostic Ultrasound: Musculoskeletal (Griffith, 2025), on a longitudinal SWE sonogram, a healthy Achilles tendon has stiff tissues (displayed in red) with an elasticity of 497 kPa. In severe tendinosis, the tissue becomes softer and heterogeneous (displayed in blue) with an elasticity of 133 kPa.
| Condition | Tissue Characteristics | Elasticity (example) |
|---|---|---|
| Normal Achilles Tendon | Stiff tissues (red) | 497 kPa |
| Severe Tendinosis | Soft, heterogeneous tissues (blue) | 133 kPa |
These values are illustrative examples from the source and not established diagnostic thresholds. A universal reference value for shear wave speed in normal conditions is not specified in fragments [clarify].
Notes on SWE Methodology
According to the EFSUMB Guidelines on Elastography in Non-Hepatic Applications (Update 2018; Săftoiu et al., 2019), different shear wave speed or elasticity modulus values are obtained depending on the equipment used, tendon position, and scanning plane. This limits direct comparison of absolute values between studies and systems.
According to the same guidelines, a healthy Achilles tendon in strain elastography (SE) is predominantly rigid: high stiffness is determined in 86.7–93% of the tendon tissue, and stiffness increases with age. In Achilles tendon tendinopathy, the strain ratio (SR, when comparing the tendon with Kager's fat pad) is higher, and the tendon itself becomes less stiff.
Frequently asked questions
What stiffness value is considered normal for the Achilles tendon?
There is no single threshold in fragments. An example of a normal tendon is given — elasticity of 497 kPa (Griffith, 2025), but values depend on the equipment, tendon position, and scanning plane [clarify].
How does stiffness change in tendinosis?
In severe tendinosis, the tissue becomes softer and heterogeneous; an example of elasticity is 133 kPa compared to 497 kPa in normal conditions (Griffith, 2025).
Why can't absolute values be transferred between devices?
According to EFSUMB (Săftoiu et al., 2019), in SWE, wave speed/elasticity modulus values vary depending on the equipment, tendon position, and imaging plane.
What does strain elastography show in tendinopathy?
According to EFSUMB (2019), in tendinopathy, the strain ratio (comparison of the tendon with Kager's fat) is higher, and the tendon is less stiff than normal.
Is there an age-related effect on stiffness?
Yes, according to EFSUMB (2019), in SE, an increase in Achilles tendon stiffness with age is noted.