Knee Electrotherapy

 Introduction

This page will look at each method of electrotherapy and the evidence to support it in the use of knee conditons specifically. 

Pulsed Shortwave Therapy 

Pulsed shortwave therapy is an electrotherapy modality that is used in practice, and there are 2 types off effects suggested.

1. Electric field – upon literature reviewing there is very little evidence to support this theory, and almost all of the literature supports the magnetic field effect.
2. Magnetic field – the main effect of the pulsed magnetic field has been documented to work at a cellular level at the cell membrane. It has been suggested to assist in the transportation of ions across the membrane.

The effects are said to be in the acute and inflammatory process and documented effects are on:

• Muscles
• Nerves
• Areas of oedema
• Haematosis
• Effusion 

Therefore this would suggest that the use of pulse short wave therapy in knee conditions that resulted in effusions and oedema is effective: i.e. ligamentous injuries, arthritis and meniscal lesions, as these can all produce inflammation and swelling. A study in 2010 by Al – Mandeel and Watson found that there were significant physiological changes (blood volume) through the use of low and high doses of pulsed shortwave therapy. Limitations of this study was that this was done in healthy subjects therefore there were no pathology within the joint and people with excess adipose tissue were ecluded as this was identified to effect the effectiveness of the therapy.

Whereas Callaghan et al in 2005 looked at the effects of PSWT on levels of inflammation in patients with OA knee. The primary outcome used was sophisticated radioleucoscintigraphy to identify levels of inflammations pre and post treatments. They found that there was little inflammation in those with OA knee to start with but that there was no significant change in their levels after PSWT.

The National Institute for Clinical Excellence (NICE) has not recommended the used of PSWT for OA but the use of TENS as an adjunct only.

There is limited evidence looking at the effect of PSWT on knee conditions specifically, therefore a search was conducted on the effectiveness of PSWT on oedema and effusions, a study was identified that looked that the use of cryotherapy versus PSWT on swelling post calcaneal fractures. There were no differences found in either group and swelling had significantly improve by day 5 anyway. Cryotherapy was recommended from this study as this was a cheaper alternative which could be transported anywhere.

The majority of the literature surrounding the used of PSWT in the knee looks at Knee OA, and due to the lack of evidence found it and guidance from NICE the use of PSWT cannot be recommended from the literature.

This Physiopedia page looks at the suggested effects of PSWT 

Transcutaneous Electrical Nerve Stimulation (TENS)

TENS is a method of electrical stimulation which primarily aims to provide a degree of symptomatic pain relief by exciting sensory nerves and thereby stimulating either the pain gate mechanism and/or the endogenousopioid system. 

Pain relief using a TENS machine with 'the pain gate' theory involves excitation of the 'A beta (Aβ) sensory fibres, and by doing so, reduces the transmission of the noxious stimulus from the ‘c’ fibres, through the spinal cord and hence on to the higher centres. The Aβ fibres appear to appreciate being stimulated at a relatively high rate (in the order of 90 - 130 Hz or pps). It is difficult to find support for the concept that there is a single frequency that works best for every patient, but this range appears to cover the majority of individuals.'  

'An alternative approach is to stimulate the A delta (Aδ) fibres which respond preferentially to a much lower rate of stimulation (in the order of 2 - 5 Hz), which will activate the opioid mechanisms, and provide pain relief by causing the release of an endogenous opiate (encephalin) in the spinal cord which will reduce the activation of the noxious sensory pathways.'

Although with all of the new research evolving about pain neuroscience the 'pain gate therory' is now being challenged. It was intially developed in 1965 by Ronald Melzack and Patrick Wall, to which Wall had later said: “The least, and perhaps the best, that can be said for the 1965 paper is that it provoked discussion and experiment”

A lot of the research for the use of TENS to manage pain has been focused on chronic pain, therefore a chochrane review was done in 2000 which concluded that TENS could not be reccomended for general chronic pain management at this stage due to the lack of consistant stimulation parametersor comments on long-term effectivness. Although a protocol has been published in 2015 for a more upto date review of the literature in the use of TENS as a pain management tool. Although there is still the debate as to wether the use of TENS in chronic pain is effective, NICE and Arthritis UK have reccomeded this as an adjunct to other treatments.

A more recent chochrane review has looked at the use of TENS in the acute stages of pain and has evaluated that all studies reviews have found it beneficial there were lots of flaws to their studies such as high risk of bias, poor sample sizes, incomplete results reported and unsucessful blinding, therefore this needs to be taken into condsideration when looking at the evidence but possibly something that can be used as an adjunct again with patinet who have acute knee pain. 

Research is limited in the field of TENS and specific knee complaints therefore it is recomended that current research around the use of TENS for pain and clinical reasoning is used. 

Ultrasound (US)

Therapeutic US is divided into twoeffects: thermal and non-thermal, but each effect can occur at any one treatment. It has been suggesed that US can help speed up and improve the quality of tissue healing.  To read more on how US can help at the different stages of healing read this Physiopedia page.

Around the knee the tissue that may be influenced by US are the patellar tendon and the ligaments. Looking at pathologies of the tendon (tendinopathy) and the effectivness of therapeutic US there is little evidence which has specifically evaluated this, therefore a search was conducted looking further afield. There have in vivo and in vitro studies and studies on animal tissue which showed positive physiological changes in tendinopathy using US but there has yet to be any positive results using live human tissue . This is confimed by a systematic review and meta analysis which was published in 2015 looking at the treatment of tendinopathy in the shoulder. They found that there were no good quality studies to base recommendation on this as a treatment modality therefore recommendation was made that US should not be used as a treatment.  It can only be concluded that evidence is lacking in proving the efficacy of US as a treatment modality for tendinopathy such as patella tendinopathy. 

Soft tissue injuries such as ligamentous injuires have historically been treated with therapeutic US, a study which looked at the MCL in rats and has shown that low-intensity pulsed ultrasound exposure is effective for enhancing the early healing of medial collateral ligament injuries. Again when the research is then applied to the human population it has it's pitfalls as highlighted by Robertson and Baker in 2001 where they found that there was little evidence that therapeutic US is more effective than placebo ultrasound, for not only treating ligamentous pathologies but with patient who are in pain or a range of musculoskeletal injuries or for promoting soft tissue healing. This was then clarified later in 2005 by Zammit and Herrington who specifically looked at the management of lateral ankle ligament sprains. They found no added benefit of using US at a set dose for lateral ligament ankle sprains.

Overall from the literature reviewed including RTC's, Systematic reviews and meta analysis it cannot be concluded that therapeutic US is of benefit to soft tissue repair, patella tendinopathy or ligamentous sprains in humans. 

Shockwave Therapy

"Shockwave therapy is essentially a large-amplitude compression wave, as that produced by an explosion or by supersonic motion of a body in a medium. Just like an ultrasound wave, the shock wave consists of a high pressure phase followed by a low pressure (or relaxation) phase. When a shock wave reaches a 'boundary', some of the energy will be reflected and some transmitted." 

The research began with looking at calcific tendons and bone healing, where as today this has moved onto chronic tendon and ligament problems.