Shear Wave Elastography in Tendinopathy: Controversial Stiffness Thresholds
Principle of the Method
In shear wave elastography (SWE), a modified transducer sends push-pulses into tissue, inducing shear waves that are tracked by diagnostic imaging. Color maps have quantitative units—m/s or kilopascals (kPa). The method is quantitative: shear wave speed (SWS) is measured in m/s, which can be converted to stiffness via Young's modulus in kPa (ACR-SRU, 2024). SWE is less operator-dependent than compression (strain) elastography and allows both qualitative and quantitative assessment.
Tendon Behavior in Tendinopathy
In musculoskeletal applications, SWE color mapping is vendor-dependent: on some devices, stiff tissue is coded red, on others blue; therefore, interpretation should rely on quantitative values (kPa or m/s) rather than color (Jacobson, 2026; Griffith, 2025). The key pattern is not color but magnitude: tendinopathic tendons—for example, Achilles or common extensor carpi radialis—demonstrate reduced stiffness compared to normal. SWE can increase sensitivity and diagnostic accuracy of ultrasound for detecting early tendinosis when standard grayscale ultrasound is negative.
| Condition | Relative Stiffness | Example Value (kPa)* |
|---|---|---|
| Normal Achilles tendon | High | 497 kPa |
| Severe Achilles tendinosis | Reduced | 133 kPa |
* Example from source illustration (Griffith, 2025); absolute SWE values depend on device and manufacturer and are not directly comparable between systems.
Controversial Stiffness Thresholds
No unified, reproducible consensus stiffness threshold between devices for diagnosing tendinopathy has been established to date. SWE values differ substantially between ultrasound system manufacturers, limiting transfer of numerical thresholds from one device to another—the same inter-device comparability problem is recognized for thyroid nodule elastography (EFSUMB, 2026; ACR-SRU, 2024). Practical conclusion: thresholds should be calibrated to the specific device and protocol rather than borrowed from publications performed on different equipment.
Clinical Niches of Application
Three areas where elastography currently appears most useful (Griffith, 2025): (1) carpal tunnel syndrome (CTS), (2) Achilles tendinopathy, and (3) plantar fasciitis. In CTS, median nerve shear wave speed is elevated and appears higher in patients with moderate and severe CTS compared to mild CTS or absence of CTS; combining grayscale measurements of the median nerve with SWE may further improve diagnostic accuracy.
Limitations
Elastography may serve as a useful adjunct to standard ultrasound but lacks sufficient specificity to function as a standalone method for characterizing soft tissue lesions or differentiating benign and malignant masses (Griffith, 2025). The absence of standardized, reproducible thresholds between devices remains a key limitation in interpreting data on tendinopathy.
Frequently asked questions
How does tendon stiffness change in tendinopathy according to SWE?
Tendinopathic tendons show lower SWE values. In the Achilles tendon example, stiffness decreased from 497 kPa (normal) to 133 kPa in severe tendinosis (Griffith, 2025).
Is there a unified stiffness threshold for diagnosing tendinopathy?
No unified inter-device stiffness threshold has been established: SWE values differ between ultrasound system manufacturers, so thresholds are calibrated to the specific device (EFSUMB, 2026; ACR-SRU, 2024).
In which musculoskeletal areas is elastography most useful?
Three most useful areas (Griffith, 2025): carpal tunnel syndrome, Achilles tendinopathy, and plantar fasciitis.
Can SWE be used as a standalone method?
No. Elastography is a useful adjunct to standard ultrasound but lacks sufficient specificity for independent characterization of soft tissue lesions (Griffith, 2025).
What is the advantage of SWE over compression elastography?
SWE is less operator-dependent, allows both qualitative and quantitative assessment, and measures shear wave speed directly (Griffith, 2025; Jacobson, 2026).