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Journal of Physical Therapy Science logoLink to Journal of Physical Therapy Science
. 2015 Dec 28;27(12):3667–3670. doi: 10.1589/jpts.27.3667

Comparison of therapeutic duration of therapeutic ultrasound in patients with knee osteoarthritis

Mustafa Aziz Yıldırıım 1,*, Demet Uçar 2, Kadriye Öneş 1
PMCID: PMC4713767  PMID: 26834328

Abstract

[Purpose] The aim of study was to compare different durations of ultrasound in patients with knee osteoarthritis. [Subjects and Methods] One hundred patients diagnosed with bilateral knee osteoarthritis (OA) were enrolled in this study. Patients were divided into two groups. The first group (G1) received 4 minutes of ultrasound. The second group (G2) received the exact same treatment, but the duration of ultrasound was longer at 8 minutes. Patients in both groups underwent a total of 10 ultrasound over 2 weeks. Following treatment, all patients provided self-evaluations of pain via the Visual Analog Scale (VAS), overall physical function with WOMAC, disability via the Lequesne index (Leq), and depressive symptoms with the Beck Depression Index (BDI). [Results] There were no significant differences in VAS, WOMAC Leq, and BDI values between groups 1 and 2. After treatment, VAS, WOMAC, Leq, and BDI values improved for both treatment groups. However, following treatment, G2 had significantly greater values for WOMAC functional and total scores than G1. No statistically significant differences were observed for VAS scores while inactive, WOMAC pain and stiffness scores, and BDI values after treatment between both groups. VAS pain scores while active and Leq index values were significantly lower in G1 than G2. [Conclusion] Patients in both groups demonstrated improved functionality, pain and psychological status following a consistent, 2-week regimen of 4-minute or 8-minute treatments with ultrasound. Yet, patients that experienced longer treatment durations of 8 minutes demonstrated better outcomes in pain and the ability to carry out activities of daily living.

Key words: Knee, Ultrasound, Osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is the most common chronic progressive joint disease in the elderly and has a significant impact on quality of life as functional status decreases as a result of the pain. Furthermore, difficulties in carrying out activities of daily living have detrimental effects on psychological well-being. In general, the goals of clinically managing knee OA are to provide pain relief and to maintain or to improve functionality. A diverse range of pharmacological, non-operative and surgical options are available for treating OA, yet each therapeutic modality has its respective limitations and side effects1). Short-wave diathermy, transcutaneous electrical nerve stimulation, ultrasound (US) therapeutic acoustic radiation, and applying hot packs are all commonly utilized noninvasive modalities to control both acute and chronic OA pain2). Therapeutic acoustic radiation is transmitted into target tissues by US via high-frequency pressure waves that are generated by piezoelectric crystals in the transducer. Heat is generated by the pressure waves, and it has been shown that low-intensity US pulses stimulate cellular metabolism that enhance tissue regenerative capacity3,4,5,6). This relatively new treatment modality has been shown to promote the repair of full-thickness tears in articular cartilage. Specifically, it has been found that the pressure waves induce stromal cell and chondrocyte proliferation in addition to mesenchymal stem cell differentiation at the lesion site7,8,9). However, the therapeutic effects of US are more pronounced in the joint spaces, such as the knee joints, because synovial fluid has high water content10). It is the one of several physical therapy modalities suggested for the management of pain and loss of function due to OA and can be used as part of an over all rehabilitation program11).

Several studies compare US and physical therapy versus placebo for patients with knee OA, but the clinical efficacy of US remains controversial2, 12,13,14,15,16,17,18,19,20,21). Despite these results, US therapeutic acoustic radiation is still very popular for the treatment of musculoskeletal disorders and it has been asserted that it reduces edema, relieves pain, and increases range of motion12–14). The aim of this prospective randomized single-blinded trial was to evaluate whether an 8-minute regimen of US therapeutic acoustic radiation is superior to a 4-minute regimen for the treatment of knee OA.

SUBJECTS AND METHODS

This prospective randomized single-blinded trial was conducted at the Istanbul Physical Medicine and Rehabilitation Training Hospital in Turkey. A total of 100 patients between the ages of 40–70 years diagnosed with knee OA and a Kellgren-Lawrence grade of 2 or 3 according to American College of Rheumatology criteria were enrolled in the study22, 23). Exclusion criteria from the study included: any contraindications against performing physical therapy, dermatological problems, any systemic disease, abnormal laboratory test results, previous history of knee surgery or arthroplasty, previously participating in a physical therapy program, previous history of hyaluronic acid or steroid intraarticular injections, or having US therapeutic acoustic radiation within the last 6 months.

Patients were evaluated at baseline and after the entire treatment regimen lasting 2 weeks by a certified physician who was blinded to patient treatment condition. Informed consent was obtained from all subjects after the nature of the study had been fully explained. The study was approved by our institution’s ethics committee and was carried out in accordance with the principles of the Declaration of Helsinki. Patients were asked to rate their pain level via a visual analogue scale (VAS) at rest and during activity. Scores ranged from 0 to 10, with a score of 0 indicating no pain and 10 indicating extremely severe pain22). The Turkish translated version of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was utilized to assess OA patient symptoms23). The 24-item WOMAC is a self-administered questionnaire that is divided into 3 subscales including pain (5 questions, score range: 0–20), joint stiffness (2 questions, score range: 0–8), and physical functionality (17 questions, score range: 0–68)24). Previous studies demonstrated that this scale is both a valid and reliable tool to evaluate patients with knee OA25, 26). Higher scores on the WOMAC indicate more severe OA symptoms and so translate to more profound physical limitations. The extent of patient disability was evaluated with the Lequesne (Leq) index27). The questionnaire is comprised of 11 items regarding knee discomfort, ability to endure ambulation, and difficulties in carrying out activities of daily living. A maximum score of 26 indicates the greatest degree of disability. The Beck Depression Inventory (BDI) was utilized to measure the intensity and severity of patient depressive symptoms. Specifically it is composed of 21 questions and a score of 9 and above was considered to be a diagnosis of depression28).

Patients were randomly divided into two groups. The first group (G1) received 4-minute US therapeutic acoustic radiation treatments, performed exercise, and received transcutaneous electrical nerve stimulation. The second group (G2) received an identical treatment, but instead these patients were treated with 8-minute regimens of US therapeutic acoustic radiation. Continuous ultrasonic waves were delivered at a 1 MHz frequency and at an intensity of 1.5 watt/cm2 via a transducer with a diameter of 5 cm (Chattanooga, USA). The patient maintained a supine position with both knees fully extended throughout treatment while US therapeutic acoustic radiation was directed around the knee joint. Aqueous gel was utilized as a coupling medium to facilitate the transmission of the high pressure waves. The transducer was moved in a circular fashion at a 90 degree angle to the knee surface during treatment. Every patient received 20 minutes of superficial heating therapy delivered via infrared radiation, 20 minutes of TENS, and 15 minutes of isometric quadriceps exercises for both knees. Patients in each group received treatments five times weekly for a total of 2 weeks. Nonsteroidal anti-inflammatory drugs and antidepressants were not permitted throughout the course of treatment, but medications for the treatment of comorbid diseases were permitted during the study. Data were analyzed using the Statistical Package for Social Sciences (SPSS) version 21.0 for Windows (SPSS Inc., Chicago, IL, USA). Demographic data were presented as the mean plus or minus one standard deviation (SD). Categorical data were analyzed via the χ2 test. The Kolmogorov-Smirnov test was utilized to determine whether continuous variables followed a normal distribution. The Mann-Whitney U-test and independent samples t-test were used to perform quantitative analyses of the data. The Wilcoxon test was used to assess whether sample means differ over repeated measurements. Statistical significance was achieved with p-values less than 0.05.

RESULTS

The mean ages of groups 1 and 2 were 56.44±9.35 years and 56.72±10.35 years, respectively. There were no statistically significant differences between sociodemographic data between each group (p>0.05; Table 1).

Table 1. Demographic features.

Group 1 Group 2
Mean±SD / n-% Mean±SD / n-%
Gender Female 29 58.0% 37 74.0%
Male 21 42.0% 13 26.0%
Age (years) 56.44 ± 9.346 56.72 ± 10.306
BMI (kg/m2) 30.24 ± 4.412 31.01 ± 4.633
Marital status Married 37 74.0% 38 76.0%
Single 0 0.0% 2 4.0%
Divorced 13 26.0% 10 20.0%
Profession House wife 17 34.0% 15 30.0%
Working 14 28.0% 17 34.0%
Retired 19 38.0% 18 36.0%
Duration (years) 4.66 ± 2.446 4.50 ± 2.375
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There were no significant differences between baseline VAS, Leq, BDI and WOMAC values between each group (p˃0.05). Following treatment, VAS, WOMAC, Leq, and BDI values decreased for both treatments groups (Tables 2 and 3). G1 demonstrated significantly lower WOMAC functional and total scores (Table 2). No statistically significant differences were observed for VAS at rest values, WOMAC pain and stiffness scores, and BDI values after treatment between G1 and G2 (p˃0.05).

Table 2. Womac values.

Group 1 Group 2
Mean±SD / n-% Mean±SD / n-%
WOMAC pain Before 11.70±4.176 11.10±4.423
After 7.54±3.098 6.62±3.356
Difference −4.16±2.034 −4.48±1.854
WOMAC stiffness Before 1.52±2.053 2.22±2.207
After 0.92±1.469 1.12±1.272
Difference −0.60±0.728 −1.10±1.460
WOMAC function Before 38.06±11.134 36.60±8.760
After 27.62±10.851 23.96±6.755
Difference −10.44±4.343 −12.64±5.244
WOMAC total Before 51.28±15.115 49.88±13.055
After 36.08±14.045 31.42±9.712
Difference −15.20±5.914 −18.46±7.083
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Womac: Western Ontario and McMaster Universities Osteoarthritis Index

Table 3. VAS, Leq and BDI values.

Group 1 Group 2
Mean±SD / n-% Mean±SD / n-%
VAS Before 2.58±2.357 2.28±2.129
After 1.44±1.554 1.00±1.262
Difference −1.14±0.948 −1.28±1.310
VAS in activity Before 6.96±1.895 6.70±1.344
After 4.46±1.775 3.48±1.389
Difference −2.50±1.074 −3.22±1.130
Leq Before 13.32±3.689 12.44±3.715
After 9.50±3.627 6.98±3.172
Difference −3.82±1.826 −5.46±2.062
BDI Before 14.38±9.352 12.72±8.461
After 11.34±7.612 9.84±7.366
Difference −3.04±2.020 −2.88±1.560
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VAS: Visual Analog Scale, Leq: Lequesne index, BDI: Beck Depression Index

VAS in activity values and Leq index values were significantly lower in G1 than G2 (Table 3).

DISCUSSION

In this study we investigated the relative effectiveness of US therapeutic acoustic radiation for patients with knee OA over 8-minute and 4-minute treatment sessions. Patients also received physical therapy sessions and transcutaneous electrical nerve stimulation throughout the study and significant improvement was noted in self-ratings of pain intensity, physical functionality, and depressive symptoms. Yet, patients randomly assigned to the 8-minute US group achieved better results in their pain and ability to perform activities of daily living in comparison to patients receiving 4-minute treatments. There are conflicting data regarding the efficacy of US therapeutic acoustic radiation treatment for knee OA29,30,31,32,33,34). Specifically, in 2010 the International Osteoarthritis Research Society recommended that the optimal management for hip and knee OA requires a combination of non-pharmacological and pharmacological modalities including physical therapy, but does not specifically mention US therapeutic acoustic radiation as an adjunct35). Several authors have researched the effectiveness of US therapeutic acoustic radiation treatment, but its clinical efficacy remains controversial2, 15,16,17,18,19,20). However, our findings indicate that US therapeutic acoustic radiation treatment may be more effective in treating knee OA than previously thought. In fact a study that Ozgonenel et al.16) compared US with sham US in the treatment of knee OA revealed that US was superior to placebo, yet there were further OA treatments provided that may have obscured whether or not the effect was due to US alone.

The intensity, the size of the area treated, and the duration of US therapeutic acoustic radiation treatment used in previously published studies varies considerably and there is little guidance in the literature as to what may be the optimal dosage to treat knee OA.

Yet, it has been recommended that for degenerative arthritis, US should be provided at a constant intensity from 0.5 to 2 watts/cm2 for 5 to 10 minutes36). Guided by these recommendations, we utilized an intensity of 1.5 watts/cm2 over 4 or 8 minutes in our study.

It has been reported that US therapeutic acoustic radiation provides pain relief and improvement in functionality for patients with knee OA15, 16,17,18,19). In our study, VAS pain scores improved and WOMAC scores were better after treatment for both treatment groups. Yet, Ulus et al.21) demonstrated no increase in WOMAC functionality scores for patients receiving US treatment versus those receiving sham US treatment.

In Sale et al.37) study, general depression is commonly observed in patients who suffer from chronic pain. Ozcetin et al.38) showed the prevalence of depressive symptoms is high among the elderly with OA. Axford et al.39) has identified an association between depression, disability, pain, and symptom severity in patients with knee OA. In our study, the BDI was used to assess the degree of depressive symptoms and a decrease in depressive symptoms was seen in both treatment groups such that their self-ratings of depression did not differ significantly. Similarly, Ulus et al.21) studied the effects of US therapeutic acoustic radiation on patient psychological well-being and there were no differences between groups after receiving treatment as well.

Huang et al.18) showed that patient perception of impairment and disability due to OA are important factors in patient ratings of disease severity. Deniz et al.40) studied effectiveness of pulsed and continuous diclofenac gel phonophoresis with topical diclofenac gel treatment in knee osteoarthritis. They showed that both continuous and pulsed ultrasound diclofenac gel phonophoresis is more effective for pain and functional status of patients with knee osteoarthritis than topical application of diclofenac gel. Yıldırım et al.41) compared the efficacy of ultrasound treatments of 4- and 8- minute durations for patients with subacromial impingement syndrome. Eight minutes of ultrasound treatment was shown to be more effective than 4 minutes of ultrasound treatment. In this study, Lequesne disability scores and WOMAC scores decreased significantly in both groups following treatment. Furthermore, the 8-minute treatment group reported a significantly better improvement in physical functionality than the 4-minute treatment group. These results suggest that longer US therapeutic acoustic radiation treatment durations may confer greater improvement in patient functionality and ability to perform activities of daily living. In all, our findings indicate that US therapeutic acoustic radiation treatment has true potential in improving symptoms for patients with knee OA. We recommend that further studies are performed in the future to develop a standardized treatment protocol to optimize the therapeutic benefit of this modality for patients with OA.

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