**4. Discussion**

**Figure 1.** Recruitment and flow of participants through the trial.

268 Pain Relief - From Analgesics to Alternative Therapies

A number of researches considered several aspects related to muscle function, such as strength and aerobic capacity as well as other clinical aspects, such as pain, stiffness, range of motion of the knee, and WOMAC in patients with OA [14–20].

Pain is one of the most common complaints and disability symptoms in patients with knee OA. The positive effects of nonpharmacologic management on knee pain and health status in OA patients were examined. Mascarin et al. [4] studied 40 patients and compared the TENS protocol with the US protocol. The TENS was applied using a frequency of 100 Hz, pulse width of 50 μs, intensity (mA) set at the individual subject's sensorial threshold, modulation up to 50% of variation frequency, quadratic biphasic symmetrical pulse and a length of application of 20 minutes. The US protocol consisted of continuous ultrasonic waves of 1


**Table 2.** Mean (SD) of the groups, mean (SD) differences within the groups, and mean (95% CI) differences between the groups for VAS (in cm) outcomes.


Groups

Before Exp (n = 30)

VAS

*Right knee* 6

(1)

*Left knee* 6

(1)

 (2)

(1)

(1) Exp = ultrasound, US; Con = extracorporeal shock wave therapy (ESWT); VAS = visual analogue scale.

**Table 2.** Mean (SD) of the groups, mean (SD) differences within the groups, and mean (95% CI) differences between the groups for VAS (in cm) outcomes.

(1)

(2)

(1–3)

 (2)

6

3

1

–3

–5

2

0.000

 1.26

(1)

(2)

(1)

(2)

(1–3)

6

3

2

–3

–4

2

0.001

 0.63

270 Pain Relief - From Analgesics to Alternative Therapies

 Con (n = 30)

 Exp (n = 30)

 Con (n = 30)

 Exp (n = 30)

 Con (n = 30)

Exp (n = 30)–Con (n = 30)

*p*

Effect size *(Cohen's d*)

After

Difference

Difference between groups

within groups

After–Before

After–Before

**Table 3.** Mean (SD) of the groups, mean (SD) differences within the groups, and mean (95% CI) differences between the groups for WOMAC (in points) outcomes.

wMHz frequency and 0.8 W/cm<sup>2</sup> power, applied with a 5-cm diameter applicator. The study results showed that TENS, as well as US, are effective for reducing pain and improving the WOMAC score. Ng et al. [21] studied 24 patients and compared electroacupuncture treatment and TENS, using the same parameters for both (low frequency = 2 Hz, continuous mode, pulsation of 200 μs for 20 minutes of application) and showed that either electroacupuncture treatment or TENS is effective in pain reduction because a prolonged analgesic effect maintained in the two groups.

Recently, ESWT has become one of the leading therapeutic alternatives. It can treat such diseases as chronic tendinopathies, nonunion of long bone fracture, and early stage of avascular necrosis of the formal head [22]. Moreover, ESWT diffused to the treatment of OA in animals [23, 24]. It improved the rats' walking ability [23]. It significantly improved the lameness degree in horses [24].

The results achieved in people only confirm these findings. Zhao et al. [25] used ESWT to treat knee OA over 12 weeks and compared it with placebo treatment. Seventy patients were randomized to receive either placebo (n = 36) or ESWT (n = 34). In the ESWT group, the patients received 4000 pulses of shockwave at 0.25 mJ/mm<sup>2</sup> a week during 4 weeks. In the placebo group, the patients got shockwave at 0 mJ/mm<sup>2</sup> in the same area for the same time. The authors found the effect on OA by pain on VAS and perceived of health on WOMAC. The evaluation was performed at baseline and after 1, 4, and 12 weeks. The authors found that ESWT was more effective than placebo in reducing pain and improving perceived of health at each time assessment of the research.

In our study following 5 weeks of the treatment the results were similar to the results of the other authors, although we applied another treatment protocol. We found that pain in knees decreased in both the experimental (US) and the control (ESWT) groups, but there were the significant between-group differences after the intervention in favor for ESWT, and also the effects sizes were always more far-reaching in the patients treated with ESWT, than those ones in the patients treated with US. In this study, we also found that both treatment methods improved the total score of WOMAC, but the health benefits in the patients treated with ESWT and their effect size were also more important than those ones in the patients from the US group.

Our study had as strengths as limitations. The strengths included the fact that the study was analyzed using the intention-to-treat principle, the patients were randomly assigned to the two groups—an experimental and a control one. The interventions were provided by the same blinded to outcome measures experienced physiotherapist. Also, they were administered by the same assistant, blind to the group allocation.

The major limitation was the short follow-up period. Therefore, the future study ought to be a minimal follow up of 1–2 years for all subjects, it would significantly increase the impact of this kind of the study, unfortunately we had no chances to prolong the study. The second limitation is the small sample size. Our findings are therefore to be read as preliminary ones in view of possible future long-term studies with a larger sample size to confirm these results and assess the impact of US and ESWT on pain and on perceived health in people suffering from knee OA.
