The Frequency of Ultrasound Therapy in Physiotherapy
Therapeutic ultrasound has become an indispensable asset to many physiotherapy practices, serving as an invaluable adjunctive treatment approach for exercise therapy, friction massage and manual modalities.
Physiotherapists can maximize their effectiveness by selecting an ultrasound wave frequency that best meets their therapeutic objectives; commonly used frequencies include 1 and 3MHz.
1. Intensity
Ultrasound therapy can be an invaluable asset for rehabilitation, helping increase blood flow, reduce pain, and promote tissue repair. Utilizing the piezoelectric effect – where electrical signals cause crystals inside an ultrasound probe to vibrate in response to electrical signals – mechanical sound waves beyond human hearing travel through tissues producing microscopic vibrations of tissue particles which allow biological responses. Therapeutic ultrasound uses continuous and pulsed modes that produce both thermal effects as well as non-thermal ones (cavitation (the formation of tiny gas bubbles that stimulate cell activity)
Thermal effects occur when tissue absorbs sound energy and heats up, increasing blood flow to damaged areas and speeding metabolic processes, helping relieve pain, reduce inflammation, and improve range of motion. Non-thermal effects, such as cavitation, can stimulate cellular activity to speed healing by increasing cell membrane permeability and stimulating collagen synthesis.
Studies have proven the efficacy of low-intensity therapeutic ultrasound in treating various musculoskeletal injuries, such as osteoarthritis and myofascial pain syndrome. While evidence for other conditions like adhesive capsulitis or tendinopathies remains limited, therapeutic ultrasound remains an increasingly popular choice among physiotherapists due to its low risk profile and versatility across different settings.
Therapeutic ultrasound is a painless, minimally-invasive procedure. After placing an ultrasound transducer over the treatment area and applying conductive gel, a therapist slowly moves their probe around in circular movements over between five and 10 minutes for maximum effectiveness.
Advanced ultrasound technologies have increased ultrasound’s utility in musculoskeletal rehabilitation. For instance, one modality called MRgUltrasound uses MRI-guided high intensity focused ultrasound to ablate deep tissue targets without harming healthy tissues – offering an alternative solution to surgical treatments for soft tissue tumors.
Low-intensity pulsed ultrasound, a relatively new modality, uses non-thermal effects to promote bone and soft tissue repair, accelerate fracture healing, and enhance drug delivery for thrombolytic therapies. While therapeutic ultrasound has many applications, its use must be conducted carefully to minimize risks posed by it; examining overlying skin for signs of burns as well as making sure equipment use meets standards is crucial to maximize outcomes and ensure patient safety. Collaboration among physical therapists, medical doctors, nurses to maximize treatment outcomes and ensure patient safety can optimize outcomes and patient safety outcomes and patient safety outcomes and safety outcomes and patient safety outcomes and safety outcomes and patient safety outcomes and patient safety is necessary to fully utilize its therapeutic potential.
2. Pulse Ratio
When the vibrating crystal in a soundhead transmits an ultrasound wave, part of it reflects off tissue interfaces and part refracts before some gets absorbed by tissues – this is known as attenuation and other factors may also impact how much energy gets absorbed at tissue interfaces during treatment, including:
The frequency of ultrasound waves (1 or 3 MHz) determines how deeply energy can penetrate tissues as certain frequencies absorb it more readily than others, which has an impactful impact on treatments like tissue compression or softening/lengthening tendons/ligaments etc.
As well as frequency, pulse ratio (i.e. duty cycle) has an effect on how much energy is absorbed at tissue interfaces. Pulse ratio can be controlled by length of time that ultrasound is on and length of off period; for example 2ms ON time to 8ms off time will create a 1:4 (20%) ratio with increased pulse ratio increasing duty cycle or number of ON:OFF cycles completed per second and thus frequency.
With higher pulse ratios, tissue temperature can increase quickly at tissue interfaces and cause discomfort and hot spot formation. Conversely, lower pulse ratios allow ultrasound energy to cool between each on-off cycle, decreasing thermal damage potential and potentially leading to discomfort or hot spots forming.
3. Frequency
Therapeutic ultrasound has long been recognized for its benefits in physical therapy; however, to optimize patient outcomes it requires an effective team approach involving physicians, physical therapists, and clinical nurse specialists.
Physiotherapists employ handheld ultrasound probes to deliver mechanical waves into tissues of the body using hypoallergenic transmission gel. Crystals within an ultrasound probe convert electrical signals into mechanical soundwaves beyond human hearing range that transfer energy directly to tissue particles, inducing oscillations and encouraging biological responses.
Low-intensity therapeutic ultrasound has become an established modality in treating various musculoskeletal conditions, while high-intensity focused ultrasonography (HIFU) has become an increasingly popular and promising procedure. Both have their own set of indications and contraindications. For instance, HIFU should not be performed on pregnant women or body regions with pacemakers, metallic implants, active infections or cancerous tissue as this could increase risks significantly.
4. Time
Duration of therapeutic ultrasound sessions depends on the nature and severity of the condition being addressed, with sessions typically lasting 5-10 minutes per area and used as part of multiple therapies – massage, manual or therapeutic exercises, or acupuncture being among them. Our PhysioD therapists may combine ultrasound therapy with one of these approaches in order to meet your pain-reduc goals more efficiently.
Therapeutic ultrasound utilizes mechanical sound waves to stimulate tissues, creating micro-vibrations within them that create heat energy and increase blood flow to an area while also providing much-needed oxygen to aid healing processes – one reason this therapy can be especially helpful for musculoskeletal injuries.
Under ultrasound imaging, a medical technician employs a probe to transmit high-frequency sound waves through your body using high frequency soundwaves. Once inside tissues, these waves travel deep until returning back out again before being relayed back out again through real time transmission to a computer screen, where images can then be interpreted by either radiologist or doctor for interpretation. Ultrasound has many applications from confirming and dating pregnancies to guiding doctors during surgical procedures.
Ultrasound can provide safe and effective relief for injuries to soft tissues such as muscles and tendons. Ultrasound therapy can break down scar tissue adhesions in injured muscle groups; decrease inflammation; promote healing; and alleviate soft tissue pain associated with injuries of all kinds, such as spasms, range of motion issues or chronic injuries.
Ultrasound waves create tiny gas bubbles when they penetrate your body, increasing local temperatures to reduce pain and stiffness while increasing lymph flow, helping speed up healing time. Therefore, therapeutic ultrasound is an excellent tool for treating ailments like joint and ligament sprains, tendonitis and bursitis.

