Therapeutic Ultrasound in Physiotherapy: Uses, Benefits, Risks and What the Evidence Says
Therapeutic ultrasound is a commonly used physiotherapy modality in which high-frequency sound waves are delivered to tissues through an ultrasound treatment head. Physiotherapists may use it as part of a rehabilitation programme for selected musculoskeletal conditions, particularly when the treatment goal includes pain management or improving tolerance to movement.
Although therapeutic ultrasound has been used in physiotherapy for decades, its clinical effectiveness is not universal. Research suggests that it may provide benefits for certain conditions, particularly some knee disorders, but results vary according to the diagnosis, treatment parameters, comparison treatment and outcome being measured. (PubMed)
This article explains how therapeutic ultrasound works, what it is used for, what patients may experience during treatment, and what current research tells us about its effectiveness.
What Is Therapeutic Ultrasound?
Therapeutic ultrasound is an electrophysical agent that uses mechanical sound waves rather than electrical current.
The ultrasound device contains a transducer that converts electrical energy into mechanical vibrations. These vibrations produce sound waves at frequencies above the range of normal human hearing.
During treatment, the physiotherapist generally applies coupling gel to the skin and moves the ultrasound head over the selected treatment area.
Therapeutic ultrasound is different from diagnostic ultrasound.
Diagnostic ultrasound creates images of internal structures.
Therapeutic ultrasound delivers acoustic energy to tissues with the intention of producing therapeutic effects.
The treatment parameters can be adjusted, including frequency, intensity, mode and duration.
How Does Therapeutic Ultrasound Work?
The effects of therapeutic ultrasound are generally discussed under two broad categories:
Thermal effects
Continuous ultrasound can increase tissue temperature.
Theoretically, this may influence:
Tissue extensibility
Local blood flow
Muscle relaxation
Pain perception
Tolerance to stretching or movement
These effects are part of the rationale for using ultrasound before certain manual therapy, stretching or exercise interventions.
However, a theoretical physiological effect does not automatically mean that a treatment produces a meaningful clinical improvement. Clinical outcomes need to be evaluated through controlled research.
Non-thermal effects
Pulsed ultrasound is intended to minimize tissue heating while producing mechanical effects.
Proposed mechanisms include acoustic streaming and other mechanical interactions at the tissue level.
These mechanisms have been investigated in laboratory and clinical research, but the translation of these effects into meaningful patient outcomes remains condition-specific.
Therefore, physiotherapists should distinguish between a biological mechanism that can occur in tissue and evidence that the treatment improves pain, function or quality of life in patients.
What Does the Research Say?
The evidence for therapeutic ultrasound is mixed.
A 2024 systematic review and meta-analysis evaluated ultrasound therapy for musculoskeletal disorders involving the knee and shoulder. Ten studies were included. The review found that ultrasound was significantly more effective than other interventions for knee disorders, while the findings for shoulder disorders were much less convincing. (PubMed)
This difference is important.
It means that the question should not simply be:
“Does therapeutic ultrasound work?”
A more useful clinical question is:
“For which condition, and for which treatment goal, does therapeutic ultrasound provide meaningful additional benefit?”
Therapeutic Ultrasound for Knee Osteoarthritis
Knee osteoarthritis is one of the conditions for which therapeutic ultrasound has been studied most extensively.
A 2024 systematic review and meta-analysis included 21 randomized controlled trials involving 1,315 patients with knee osteoarthritis. The analysis found improvements in pain and WOMAC outcomes compared with control treatments. The researchers also found that treatment parameters such as mode, intensity, frequency and treatment duration could influence outcomes. No ultrasound-related adverse events were reported in the included trials. (PubMed)
However, these findings should be interpreted alongside earlier evidence.
A previous systematic review and meta-analysis found statistically significant improvements in knee pain and physical function, but rated the overall quality of evidence as very low because of the limited number and methodological quality of the available trials. (PubMed)
This illustrates an important evidence-based point:
Positive results in individual trials or meta-analyses do not automatically mean that ultrasound should be used routinely for every person with knee osteoarthritis.
It may be considered as an adjunct to a broader rehabilitation programme.
Therapeutic Ultrasound for Shoulder Pain
The evidence for shoulder conditions is less consistent.
A systematic review examining therapeutic ultrasound for chronic knee, shoulder and hip pain found that all seven included shoulder studies reported some reduction in pain, but four studies found ultrasound inferior to the comparator treatment. The authors concluded that the evidence for shoulder pain was less convincing than the evidence for knee arthritis. (PubMed)
The 2024 systematic review also found substantial uncertainty regarding shoulder disorders, with no significant difference between ultrasound and other interventions in its pooled analysis. (PubMed)
Therefore, therapeutic ultrasound should not be presented as a universally effective treatment for shoulder pain.
The underlying diagnosis matters.
Shoulder pain can arise from multiple conditions, including rotator cuff-related disorders, adhesive capsulitis, osteoarthritis and other problems. A modality that may be useful in one situation may provide little additional benefit in another.
Therapeutic Ultrasound for Plantar Fasciitis
Plantar fasciitis is another condition in which therapeutic ultrasound has been investigated.
A 2024 systematic review of randomized controlled trials included five studies examining therapeutic ultrasound for plantar fasciitis. The review reported evidence suggesting reductions in pain and functional disability, with some studies also reporting improvements in measures such as tenderness, tissue thickness and balance. (PubMed)
However, the number of studies was small.
This means the findings are encouraging but should not be interpreted as proof that ultrasound should replace other evidence-based approaches to plantar heel pain.
Therapeutic Ultrasound for Myofascial Pain
A 2024 systematic review and meta-analysis evaluated low-intensity ultrasound for myofascial pain syndrome.
The review included 16 randomized controlled trials involving 1,063 participants. Compared with sham or no treatment, ultrasound produced an additional reduction in pain, although there was substantial heterogeneity between studies. The researchers also noted considerable variation in ultrasound parameters such as frequency, intensity and treatment duration. (PubMed)
This variation is clinically important.
If different studies use different treatment parameters, it becomes difficult to determine exactly which ultrasound protocol is responsible for an observed benefit.
The review found no reported adverse events in the included studies, although safety reporting in clinical research should always be interpreted cautiously. (PubMed)
Conditions Where Therapeutic Ultrasound May Be Considered
Depending on the clinical assessment and local practice, therapeutic ultrasound may be considered as an adjunctive modality for conditions such as:
Knee osteoarthritis
Selected shoulder disorders
Plantar fasciitis
Myofascial pain
Some soft-tissue conditions
Selected musculoskeletal pain conditions
The level of evidence varies substantially between these conditions.
Therapeutic ultrasound should therefore be incorporated according to the diagnosis, treatment goals and available evidence, rather than simply because a particular body region is painful.
Potential Benefits of Therapeutic Ultrasound
Depending on the condition and treatment parameters, potential benefits may include:
Pain reduction
Several systematic reviews have reported reductions in pain for selected musculoskeletal conditions, particularly knee osteoarthritis. (PubMed)
Improved function
Some studies report improvements in functional measures, although the magnitude and consistency of these improvements vary. (PubMed)
Possible improvement in treatment tolerance
If ultrasound produces short-term symptom relief, it may potentially make subsequent movement, stretching or exercise more comfortable for some patients.
Non-invasive treatment
Therapeutic ultrasound does not require injections, medication or surgery.
Generally good short-term tolerability
Recent systematic reviews have reported few adverse events associated with therapeutic ultrasound when appropriately applied. (PubMed)
What Happens During a Therapeutic Ultrasound Session?
A typical treatment may follow these steps:
The physiotherapist assesses the patient's condition.
The treatment area is identified.
The skin is inspected for contraindications or irritation.
Ultrasound coupling gel is applied.
The therapist selects appropriate treatment parameters.
The ultrasound head is placed against the skin.
The transducer is moved continuously over the treatment area.
The patient is monitored for excessive heat, discomfort or other symptoms.
The treatment is stopped and the patient's response is reassessed.
The patient may feel little sensation, mild warmth or a gentle movement of the treatment head across the skin.
Therapeutic ultrasound should not normally be painful.
If the patient experiences excessive heat, burning or significant discomfort, the therapist should be informed immediately.
How Long Does a Treatment Session Take?
There is no single evidence-based duration that applies to every condition.
Treatment duration depends on factors such as:
Treatment area
Diagnosis
Ultrasound frequency
Intensity
Continuous versus pulsed mode
Size of the treatment area
Overall rehabilitation programme
Research studies have used different treatment protocols, which is one reason why ultrasound research can be difficult to compare across studies.
Continuous vs Pulsed Ultrasound
Therapeutic ultrasound can generally be delivered in continuous or pulsed modes.
Continuous ultrasound
The ultrasound energy is delivered continuously and produces greater thermal effects.
It may be selected when the treatment objective involves tissue heating.
Pulsed ultrasound
The ultrasound is delivered intermittently.
This reduces the average energy delivered and is generally associated with less tissue heating.
A 2024 meta-analysis of knee osteoarthritis found that treatment parameters, including mode and intensity, influenced outcomes. The study reported favorable pain outcomes with particular pulsed-ultrasound protocols, although the authors emphasized that ultrasound parameters need further investigation. (PubMed)
Therefore, clinicians should avoid assuming that one ultrasound setting is appropriate for every condition.
Is Therapeutic Ultrasound Safe?
When appropriately selected and applied, therapeutic ultrasound is generally well tolerated.
However, it is not appropriate for every patient or every body region.
Potential problems can include:
Excessive tissue heating
Burns if inappropriate parameters or technique are used
Discomfort
Skin irritation related to coupling products
Potential tissue injury if applied incorrectly
The risk depends on treatment parameters, treatment area, patient factors and application technique.
Contraindications and Precautions
Therapeutic ultrasound requires appropriate clinical screening.
Depending on the equipment, treatment parameters and clinical guidelines, ultrasound should generally be avoided or used with particular caution over areas such as:
Known or suspected malignancy
Active infection
Areas with impaired sensation where excessive heating may not be detected
Certain acute inflammatory conditions
Certain areas with impaired circulation
The eyes
Reproductive organs
Certain areas during pregnancy
Open or compromised tissue when appropriate coupling/application cannot be achieved
Areas where treatment could interfere with an implanted device or underlying medical condition
Specific contraindications can vary according to the type of ultrasound, treatment intensity and manufacturer recommendations.
For this reason, a qualified clinician should determine whether ultrasound is appropriate rather than relying on a generic contraindication list.
Can Therapeutic Ultrasound Heal Tissue Faster?
This is a common claim in physiotherapy marketing, but it requires caution.
Ultrasound can produce measurable physical effects in biological tissues, and researchers have proposed several mechanisms through which it might influence tissue behavior.
However, demonstrating a physiological effect is not the same as demonstrating faster recovery in patients.
Clinical evidence is much stronger for certain symptom outcomes in selected conditions than for a universal claim that ultrasound accelerates healing of every injured tissue.
Therefore, claims such as “ultrasound always speeds up tissue healing” are not supported by the available evidence.
Is Therapeutic Ultrasound Better Than Exercise?
It depends on the condition and the treatment objective.
Ultrasound is a passive modality. Exercise is an active intervention that can target:
Muscle strength
Physical capacity
Mobility
Balance
Functional performance
Load tolerance
For many musculoskeletal disorders, active rehabilitation is an important component of management.
Therapeutic ultrasound may be considered as an adjunct, particularly when there is evidence that it can improve a relevant symptom or facilitate participation in rehabilitation.
It should not automatically be regarded as a substitute for exercise or other appropriate active treatment.
Therapeutic Ultrasound as an Adjunct Treatment
One of the most reasonable ways to understand ultrasound is as a potential adjunct rather than a stand-alone cure.
For example, a physiotherapist might combine appropriate modality use with:
Therapeutic exercise
Manual therapy when indicated
Education
Activity modification
Progressive loading
Mobility exercises
Strengthening
Functional rehabilitation
The specific programme should be based on the patient's diagnosis and goals.
Common Myths About Therapeutic Ultrasound
Myth 1: “Ultrasound works for every type of pain.”
Reality: Evidence varies considerably by condition. Research is more supportive for some knee conditions than for some shoulder conditions. (PubMed)
Myth 2: “The hotter the ultrasound feels, the better it works.”
Reality: More heat does not automatically mean greater therapeutic benefit. Treatment intensity and thermal exposure need to be clinically appropriate.
Myth 3: “Ultrasound can replace exercise.”
Reality: Ultrasound is generally better viewed as an adjunct rather than a replacement for active rehabilitation.
Myth 4: “If ultrasound has a biological effect, it must improve recovery.”
Reality: Physiological effects and clinically meaningful patient outcomes are not the same thing.
Myth 5: “All ultrasound machines and treatment protocols are equivalent.”
Reality: Frequency, intensity, duty cycle, treatment duration and other parameters can differ substantially, and these differences may influence treatment effects.
Frequently Asked Questions
Does therapeutic ultrasound hurt?
It should generally be comfortable. Patients may experience mild warmth or very little sensation. Excessive heat or pain should be reported to the therapist.
How many ultrasound sessions are needed?
There is no universal number. The appropriate treatment frequency and duration depend on the diagnosis, treatment parameters and response to rehabilitation.
Can ultrasound reduce inflammation?
Ultrasound has proposed biological effects that may influence tissue processes, but claims about reducing clinically meaningful inflammation should be made cautiously because evidence varies by condition.
Can therapeutic ultrasound treat arthritis?
It has been studied particularly in knee osteoarthritis, with recent meta-analysis evidence showing improvements in pain and function. However, evidence quality and treatment effects vary, and ultrasound should not be considered a cure for osteoarthritis. (PubMed)
Is ultrasound useful for shoulder pain?
Evidence is mixed. Some studies report improvement, but systematic reviews have also found ultrasound inferior to comparator treatments in several shoulder studies. (PubMed)
Can ultrasound be used for plantar fasciitis?
It has been studied for plantar fasciitis, and a 2024 systematic review reported reductions in pain and functional disability. However, the evidence base remains relatively small. (PubMed)
Is therapeutic ultrasound the same as diagnostic ultrasound?
No.
Diagnostic ultrasound is primarily used to create images of tissues and structures. Therapeutic ultrasound delivers acoustic energy for a treatment purpose.
Is therapeutic ultrasound safe?
When appropriately applied to suitable patients, it is generally well tolerated. Clinical screening and correct treatment parameters remain important.
Evidence-Based Takeaway
Therapeutic ultrasound is a long-established physiotherapy modality with a plausible physiological basis and a substantial research literature.
The current evidence does not support describing it as universally effective.
Instead, research suggests a more nuanced picture:
Knee osteoarthritis: evidence from recent meta-analysis suggests improvements in pain and function, although earlier evidence raised concerns about study quality. (PubMed)
Shoulder disorders: evidence is mixed, with some studies showing benefit and others finding ultrasound inferior to comparison treatments. (PubMed)
Plantar fasciitis: a 2024 systematic review found evidence of improvements in pain and functional disability, but only a small number of studies were available. (PubMed)
Myofascial pain syndrome: recent evidence suggests low-intensity ultrasound may reduce pain, but there was substantial variation between treatment protocols. (PubMed)
Safety: recent reviews generally report few adverse events when ultrasound is appropriately used. (PubMed)
Final Thoughts
Therapeutic ultrasound can be a useful tool in the physiotherapist's treatment toolkit, but it should be used selectively.
The strongest approach is not to ask whether ultrasound is simply “good” or “bad.” Instead, clinicians should consider the patient's diagnosis, treatment objective, available evidence, appropriate parameters and response to treatment.
For many patients, ultrasound is best considered one component of a broader rehabilitation programme, rather than the primary treatment itself.
References
Guan H, Wu Y, Wang X, Liu B, Yan T, Abedi-Firouzjah R. Ultrasound therapy for pain reduction in musculoskeletal disorders: a systematic review and meta-analysis. Therapeutic Advances in Chronic Disease. 2024. (PubMed)
Luo Y, Rahmati M, Kazemi A, et al. Effects of therapeutic ultrasound in patients with knee osteoarthritis: A systematic review and meta-analysis. Heliyon. 2024. (PubMed)
Li X, Lin Y, He P, Wang Q. Efficacy and safety of low-intensity ultrasound therapy for myofascial pain syndrome: a systematic review and meta-analysis. BMC Musculoskeletal Disorders. 2024. (PubMed)
Alhakami AM, Babkair RA, Sahely A, Nuhmani S. Effectiveness of therapeutic ultrasound on reducing pain intensity and functional disability in patients with plantar fasciitis: a systematic review of randomised controlled trials. PeerJ. 2024. (PubMed)
Loyola-Sánchez A, et al. Therapeutic ultrasound for knee osteoarthritis: A systematic review and meta-analysis with grade quality assessment. 2021. (PubMed)
Therapeutic Ultrasound for Chronic Pain Management in Joints: A Systematic Review. Pain Medicine. 2019. (PubMed)
