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analgesia by different mechanisms: by causing interactions between types of nerve fibres, resulting
in a ‘block’ on the transmission of pain signals to the brain; or by releasing hormones that block
pain receptors in the central nervous system.
Results of CSP survey: Sixteen percent of respondents said that they might use or recommend
TENS at some stage in the management of contracted (frozen) shoulder.
Interferential
Background: Low frequency electrical currents are known to have analgesic effects in the tissues
(see TENS above for postulated mechanisms), but a low frequency current sufficiently strong to
reach deeper tissues would be painful on the skin. Medium frequency currents are more
comfortable on the skin, but lack analgesic effects in the deeper tissues. Interferential aims to
circumvent this problem. In classical (‘four polar’ or ‘quadripolar’) interferential, which uses four
electrodes, two medium-frequency currents are applied to the skin surface in such a way that they
interact in the deeper tissues, generating a low-frequency stimulus and the desired therapeutic
response. Another type of interferential exists, called bipolar interferential. This differs from the
traditional type in that the medium frequency currents interact within the machine, rather than the
patient’s tissues. As far as is known, the two types of interferential are interchangeable in terms of
their physiological effects (reviewed by Watson, 2009).
Results of CSP survey: Six percent of respondents said that they might use or recommend
interferential at some stage in the management of contracted (frozen) shoulder.
Short-wave diathermy (SWD) and pulsed shortwave diathermy (PSWD)
Background: SWD is radio-frequency energy which generates heat in the tissues. The heating effect
is thought to be deeper than that obtainable using, for example, hot packs or a heat lamp.
However, there is still disagreement over which tissues are preferentially heated by SWD. In recent
years, PSWD has become relatively more prevalent than SWD. In this mode, SWD is applied in
pulses, between which heat is able to dissipate to a greater or lesser extent (depending on the
intensity, the length of the pulses, and the interval between them). In general, the therapeutic
effects of heating include analgesia, reduced muscle spasm, reduced joint stiffness, increased
metabolism and increased blood flow, all of which could, theoretically, be beneficial at some stage
or other of contracted (frozen) shoulder.
Results of CSP survey: Eight percent of respondents said that they might use or recommend SWD
or PSWD at some stage in the management of contracted (frozen) shoulder.
Therapeutic ultrasound
Background: Sound is mechanical vibration and ultrasound is mechanical vibration at very high
frequencies—well above the audible range. Ultrasound does have a heating effect, although, as
with PSWD (see above) it may be pulsed to allow heat to dissipate, and it is uncertain whether any
effects are due to thermal or non-thermal mechanisms. Theoretical benefits include those
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