Therapeutic ultrasound (TUS) remains a cornerstone in physical rehabilitation. Utilising acoustic energy at 1 MHz and 3 MHz, it offers both thermal and non‑thermal effects that aid soft tissue healing, pain relief, inflammation control, and functional recovery.
How Does It Work?
Ultrasound is delivered through an applicator transmitting piezoelectric waves, causing compression–rarefaction cycles in tissues. This produces:
- Thermal effects: Heating tissues to enhance extensibility and circulation
- Non‑thermal effects: Micro‑cavitation and acoustic streaming promoting cellular processes ncbi.nlm.nih.gov+7verywellhealth.com+7pmc.ncbi.nlm.nih.gov+7en.wikipedia.org+1en.wikipedia.org+1
At 1 MHz, the waves penetrate deeply (~5 cm), ideal for treating muscles and joints. At 3 MHz, penetration is superficial (~1–2 cm), suitable for tendons, ligaments, and scar tissue .
Key Benefits
1. Enhanced Blood Flow & Healing
Both 1 and 3 MHz ultrasound increase endothelial function. A study documented a 4 % increase in flow‑mediated dilation after a single 5‑minute session on the brachial artery verywellhealth.com+15researchgate.net+15jospt.org+15, illustrating improved microcirculation that supports tissue recovery.
2. Pain Reduction and Improved Function
Systematic reviews in musculoskeletal conditions, including low back pain, myofascial pain, and osteoarthritis, highlight moderate pain relief, enhanced range of motion, and quality of life improvements ncbi.nlm.nih.gov+4frontiersin.org+4researchgate.net+4en.wikipedia.org. In chronic pain patients, ultrasound reduced disability and depression scores alongside physical gains en.wikipedia.org+15archivesofrheumatology.org+15bmcmusculoskeletdisord.biomedcentral.com+15.
3. Tissue Extensibility
Both frequencies elevate tissue temperature by ~4 °C, facilitating stretching of muscles, fascia, and scar tissue physio-pedia.com+2jospt.org+2researchgate.net+2.
4. Molecular Stimulation & Injury Repair
Low‑intensity pulsed ultrasound (LIPUS) stimulates tendon, cartilage, and muscle repair at the cellular level. Studies show it promotes collagen synthesis and reduces inflammation in both animals and humans frontiersin.org+1en.wikipedia.org+1.
Clinical Applications
Soft Tissue Injuries
● Muscle strains and sprains: Accelerated healing via micro‑cavitation and increased blood flow.
● Tendinopathies (rotator cuff, Achilles): Promotes collagen remodelling and reduces pain.
● Scar tissue: Applying 3 MHz frequency improves extensibility of fibrotic tissue.
Chronic Conditions
● Osteoarthritis: Clinical trials show pain relief and function improvement in knee OA pmc.ncbi.nlm.nih.gov.
● Chronic low back pain: Improves pain and daily function metrics en.wikipedia.org+13ncbi.nlm.nih.gov+13archivesofrheumatology.org+13.
Vascular and Endothelial Support
Improves microvascular health and decreases oedema risk in rehabilitation contexts following vascular disorders ncbi.nlm.nih.gov+4researchgate.net+4en.wikipedia.org+4.
Thermal vs. Pulsed Modes
| Mode | Effect | Best Suited For |
|---|---|---|
| Continuous | Tissue heating | Deep stretching, tight muscles, scar tissue |
| Pulsed (LIPUS) | Non‑thermal biostimulation | Cellular repair, tendon/cartilage healing |
Use 1 MHz continuous for deep muscle warming and 3 MHz pulsed for superficial tissue repair.
Examples & Case Studies
- Hauck et al. (2017): 1 & 3 MHz ultrasound improved endothelial function by 4 % versus placebo https://www.researchgate.net/publication/321628230_Comparison_of_the_effects_of_1MHz_and_3MHz_therapeutic_ultrasound_on_endothelium-dependent_vasodilation_of_humans_A_randomised_clinical_trial?utm.
- Morales‑Hernandez et al. (2023): Demonstrated ~4 °C thermal rise in gastrocnemius muscle using 3 MHz continuous ultrasound mdpi.com.
- Frontiers review (2022): LIPUS supports tendon and cartilage repair through molecular pathways https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.1080430/full?utm.
- Turkish rheumatology study: Chronic low back pain patients showed functional improvements, including walking and depression, after ultrasound therapy https://archivesofrheumatology.org/full-text/350?.
- Systematic review (2024): LIPUS in myofascial pain syndrome relieved symptoms safely with no adverse effects .
Safety and Contraindications
Therapeutic ultrasound is generally safe with rare adverse events. Contraindications include:
- Active bleeding or infections
- Malignancies
- Over growth plates (in children)
- Near pacemakers or pregnancies
Current evidence suggests low‑intensity ultrasound is highly safe, even with frequent use academic.oup.com+2verywellhealth.com+2en.wikipedia.org+2frontiersin.org+3bmcmusculoskeletdisord.biomedcentral.com+3ncbi.nlm.nih.gov+3.
Integrating Ultrasound into Treatment
At Bruno Physical Rehabilitation, we combine ultrasound with:
- Kinesiotherapy: Warm tissue with ultrasound, then stretch/move
- Laser and microcurrent therapy: Enhance cellular repair
- EMS applications: Improve muscle activation post-recovery
A typical session uses 1 MHz continuous at 0.8–1.5 W/cm² for 5–10 minutes per area. LIPUS protocols vary by condition and are prescribed 2–3 times weekly.
Conclusion
Therapeutic ultrasound at 1 MHz and 3 MHz offers evidence-based, safe, and versatile treatment for a wide array of musculoskeletal and vascular conditions. Whether used for deep muscle thermotherapy, soft tissue healing, or molecular regeneration, it can significantly enhance recovery, reduce pain, and improve physical function — especially when combined with active therapies.
For personalised ultrasound therapy plans, book a consultation at Bruno Physical Rehabilitation and discover a scientifically grounded path to healing and performance.
References
- Hauck M, et al. Comparison of the effects of 1 MHz and 3 MHz therapeutic ultrasound on endothelial function. DOI:10.1016/j.physio.2017.08.010 en.wikipedia.org+15researchgate.net+15researchgate.net+15en.wikipedia.org
- Morales‑Hernandez AG, et al. Short-term thermal effect of continuous 3 MHz ultrasound on gastrocnemius. “Diagnostics” 2023;13(16):2644 mdpi.com
- Qin H, et al. The therapeutic effects of LIPUS in musculoskeletal injuries: molecular mechanisms. Frontiers 2022 frontiersin.org
- Systematic review in BMC Musculoskeletal Disorders 2024 en.wikipedia.org
- Turkish Rheumatology study: improvements in pain and function in chronic low back pain en.wikipedia.org
- StatPearls on ultrasound therapy en.wikipedia.org+2ncbi.nlm.nih.gov+2journals.sagepub.com+2
- VeryWell Health: overview of therapeutic ultrasound verywellhealth.com
