Despite the large popularity and nearly 100 years of use of physical therapy modalities, there is still doubt about the appropriateness of these conservative therapies to treat KOA (McAlindon et al., 2014). In contrast, important reviews have stated that some diathermic therapies, such as ultrasound (Rutjes et al., 2010) or short-wave diathermy (Wang et al., 2017), may be beneficial for patients with KOA. Moreover, in the recent literature other types of physical therapy based on diathermy have been demonstrated to be effective in patients with KOA with satisfactory results. Giombini et al., 2011, in a RCT, investigated the effectiveness of microwave diathermy treatment for functional limitations and pain secondary to KOA. Their study demonstrated a significant improvement in WOMAC scores in patients with KOA compared with the control group. In another RCT, Zhao et al., 2013, demonstrated that a protocol of 4000 pulses of shockwave at 0.25 mJ/mm weekly for 4 weeks is effective in reducing pain and improving knee function, with better results than placebo. Similarly, Rabini et al. (2012), demonstrated that deep heating therapy through microwave diathermy induced a change of −18.7 points in the WOMAC score at 6 months in patients with KOA.
Previous studies showed that CRET acts by generating a warming up of deep tissues that promote cellular metabolism and oxygen delivery to tissues by increasing vascular circulation, facilitating catabolites elimination in metabolism (Tashiro et al., 2017) and stimulating the proliferation of stem cells to repair injured tissues (Hernández-Bule et al., 2014). Our prospective RCT showed that treatment based on CRET can reduce pain, stiffness and functional limitations in patients with KOA.
In the indexed literature, no previous studies exist demonstrating the effectiveness of CRET in the treatment of pain related to KOA. We found only five articles showing its effectiveness in pain treatment for other orthopedic diseases, that is, neck pain (Raffaetà et al., 2007), cervico-omo-brachial pain (Takahashi et al., 2000), back pain (Stagi et al., 2008; Notarnicola et al., 2017), postoperative-surgical pain after femoral fracture surgery (Terranova et al., 2008), shoulder pain secondary to impingement syndrome (Sanguedolce et al., 2009) and insertional tendonitis (Costantino et al., 2005). Our study showed that a 2-week program of CRET was able to significantly improve strength, physical function and pain in a sample of patients with KOA. In the study group, a reduction in the WOMAC and VAS scores compared with T0 was observed at each follow-up evaluation. In particular, differences in the WOMAC score between T0 and T1 and between T2 and T3 were greater than 15 points, which is the MCID for this tool (Tubach et al., 2005). No significant changes of WOMAC and VAS scores were observed in the control group across all time points. In the study group, a significant increase in the MRC score relative to T0 was observed at T2 and T3, but not at T1. In contrast, in the control group, a significant reduction in the MRC score relative to T0 was observed at each follow-up. These results might be explained by the fact that moderate and severe pain is associated with reduced quadriceps strength in KOA (Riddle and Stratford, 2011).
CRET treatment was well tolerated by patients; indeed, no adverse effects were observed or reported in the study group during the treatment and at the follow-up visits.
Our study has three main limitations: (i) patients recruited were affected by mild and moderate KOA (grades I–III of the Kellgren–Lawrence scale) but not severe, (ii) the follow-up duration of 3 months might be not have been completely sufficient for evaluating long-term response to the treatment, and (iii) the number of drop outs. A further possible limitation might be the impossibility to completely standardize the treatment provided, as the intensity of power provided had to be tailored to the patient’s need, compliance and tolerance (Pavone et al., 2013). However, in rehabilitation, this is a common issue, as it is not possible to standardize intensity of exercises, functional training and manual therapy (Kersten et al., 2010).
There are no conflicts of interest.
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