|Year : 2012 | Volume
| Issue : 2 | Page : 129-136
High resolution ultrasound evaluation of synovial thickness as a marker to assess response to deep tissue heating for pain relief in knee osteoarthritis
Bhawana Anand, Amit Kharat, Amarjit Singh, John Franklin, Satish Naware, Sarabjit Singh Thind
Department of Radio Diagnosis, Padmashree Dr. D.Y. Patil Medical College, Sant Tukaram Nagar, Pune, Maharashtra, India
|Date of Web Publication||10-Nov-2012|
13, Mayur 126 Prabhat Colony, Santacruz (East), Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: High-resolution ultrasound (HRUS) is a useful tool in assessing synovial tissue response to deep tissue heating (DTH)/short wave diathermy (SWD) for pain relief in knee osteoarthritis. Shortwave (SW) diathermy can be used to improve vascular circulation and reduce inflammation and pain in patients with osteoarthritis. The purpose of this study was to assess the role of ultrasound in investigating whether repetitive SW diathermy, could reduce synovial thickening in patients with knee osteoarthritis. Materials and Methods: Synovial thickness measurement of superior, medial, and lateral patellar recesses was done using ultrasonography over a span of nineteen months from April 2010 to Nov 2011 following three sessions of short wave diathermy. The sum of these three measurements was taken as the total synovial thickness and pre and post test analysis was done using primer statistical software. Result: Synovial thickening continued to become significantly thinner with sessions of treatment and after the twelfth SW diathermy treatment, there was 20.58% reduction in the synovial thickening. Conclusion: Synovial thickness is a sensitive marker in gauging the response to short wave diathermy therapy. Synovial thickness is an objective marker to assess pain relief in knee osteoarthritis following deep tissue heating.
Keywords: Deep tissue heating, high-resolution ultrasound, knee osteoarthritis, short wave diathermy, synovial thickness assessment
|How to cite this article:|
Anand B, Kharat A, Singh A, Franklin J, Naware S, Thind SS. High resolution ultrasound evaluation of synovial thickness as a marker to assess response to deep tissue heating for pain relief in knee osteoarthritis. Med J DY Patil Univ 2012;5:129-36
|How to cite this URL:|
Anand B, Kharat A, Singh A, Franklin J, Naware S, Thind SS. High resolution ultrasound evaluation of synovial thickness as a marker to assess response to deep tissue heating for pain relief in knee osteoarthritis. Med J DY Patil Univ [serial online] 2012 [cited 2018 Feb 23];5:129-36. Available from: http://www.mjdrdypu.org/text.asp?2012/5/2/129/103341
| Introduction|| |
Osteoarthritis (OA) is a chronic degenerative disorder of multifactorial etiology characterized by loss of articular cartilage, hypertrophy of bone at the margins, subchondral sclerosis and range of biochemical and morphological alterations of the synovial membrane and joint capsule. Osteoarthritis is the second most common rheumatological problem and is the most frequent joint disease with prevalence of 22% to 39% in India. ,, The hip and knee are the most common joints to be involved in patients of osteoarthritis which is probably due to alteration in chondrocyte responsiveness to different cytokines.  Typical clinical symptoms are pain, particularly after prolonged activity and weight bearing; whereas stiffness is experienced after inactivity.  Early detection and treatment can help in alleviating the symptoms and slow the progression of the disease. Knee osteoarthritis is often associated with synovitis, an inflammatory process of the surrounding synovium.  In chronic synovitis, the synovial villi become prominent and thickened and excrete more synovial fluid. ,, In a chronic osteoarthritic joint, fragments of cartilage break off and irritate the synovium, causing synovial inflammation, which with time progress to chronic inflammation.  Synovitis is associated with knee pain, swelling, suprapatellar fullness and synovial thickening. Synovial thickness is known to be a prognostic marker of cartilage loss.  Therefore; synovial thickness may be regarded as an index in assessing the extent of the synovitis.
High resolution ultrasonography is an inexpensive, simple to use, non invasive, multiplanar imaging technique that has advanced substantially over the past decade. It allows direct visualization of the soft tissues and joint compartments with no risk of exposure to ionizing radiation or intra articular and/or intravenous contrast agent. Ultrasound is valuable in early detection of OA and is helpful in defining the type and extent of bone and cartilage damage. It is also an excellent tool for the detection of effusion and synovitis, which correlate with joint pain, and is playing an important role in assessing the significance of the inflammatory component of osteoarthritis. 
The power doppler component of the ultrasound is very sensitive to assess early inflammatory changes/vascularity in the synovium.
Knee osteoarthritis treatment aims at alleviating pain, improving function, preventing and correcting deformities, and retarding disease progression. , Many interventions have been used for this, including changes in the affected individual's lifestyle, drugs, surgical and physical therapy that use specific techniques such as exercise, and other physical resources. ,
Among the techniques used in physical therapy, electromagnetic radiation is commonly referred to as short wave (SW), and can be applied in a continuous or pulsed form. 
Shortwave diathermy is a non - pharmacologic management approach , that involves the application of deep heat to reduce pain and swelling, accelerate the inflammatory process and promote healing in tissues with chronic inflammation. Studies have been done in assessing the presence of synovial thickness in patients with degenerative osteoarthritis , and in validating the use of ultrasound as a good tool for measuring synovial thickness. ,, The effects of SWD in increasing tissue temperature and circulation and reducing pain in patients with degenerative osteoarthritis have also been well documented. ,,,,
Continuous shortwave diathermy is the technique of choice when uniform marked elevation of temperature is required in the deep tissues. This heating can be targeted accurately by using an appropriate applicator positioned correctly. SWD also allows superficial structures to be heated selectively, although for this the various methods of surface heating are usually preferable. Sub-acute or chronic conditions respond best to continuous shortwave diathermy which, when used properly, can be as effective as ultrasound. Acute lesions are better treated with pulsed shortwave diathermy. Continuous shortwave diathermy can help to relieve pain and muscle spasm, resolve inflammatory states and reduce swelling, promote vasodilatation, increase the compliance of connective tissue, increase joint range and decrease joint stiffness. 
The purpose of our study was to evaluate the role of high resolution ultrasound (HRUS) in sequentially measuring the synovial thickness in a symptomatic patients of knee osteoarthritis following Short wave diathermy (SWD) and to assess it as objective quantitative tool in validating the efficacy of SWD.
| Materials and Methods|| |
Place of Study
A Tertiary Care Teaching Medical College, Hospital and Researh centre, Pune, India.
Period of Study
April 2010 to Nov 2011.
- Degenerative osteoarthritic knee of grade III or less based on Kellgren and Lawrence grading of knee osteoarthritis on radiography.
- Patients having synovial thickness when diagnosed with ultrasonography.
- Full ROM except minimal tightness in the knee joint and not engaged in any high joint loading exercises. ,
- Had not undergone any specific treatment 3 months before entering the study.
- Patients with any clinical musculoskeletal problems associated with knee joint such as fractures, tendon or ligament tears or meniscus injury.
- Problems associated with hip/ankle/foot joints.
- Central or peripheral neuropathy.
- Diabetes mellitus.
- Siemens × 300 ultrasound scanner-linear transducer (Multi frequency) with small foot print.
Initially there were 33 patients who fulfilled the criteria, but 13 were unable to take short wave diathermy therapy at regular intervals. Therefore 20 subjects participated in this study.
Adequate history was taken, to include the subjects in the study. After getting the written consent from these subjects they were instructed about the study protocol. The study protocol consists of assessing the severity of pain based on Numerical Pain Rating Scale (NPRS scale), grading osteoarthritic changes on the basis of Kellgren Lawrence classification system, [Table 1]  pre treatment evaluation of pain and synovial thickness, intervention followed by post treatment evaluation of the same above.
The depth of synovial tissue was a constant parameter in assessing temporal change in synovial thickness.
A Numerical Pain Rating Scale (NPRS) was used for the assessment of knee pain [Figure 1]. It is an ordinal scale, using a 10 cm line divided into 10 equal sections, with 0 representing "no pain" and 10 representing "unbearable pain". Each participant was asked to indicate on the scale, the level of pain in his or her knee joint before and after treatment. ,
High Resolution Ultrasonography
Ultrasonography was performed on the osteoarthritic knee at the initial and at three follow-up sessions using Siemens × 300 ultrasound system. Patient was placed in supine position with the knee in neutral position (The tested leg was stabilized on a tripod with the knee joint at 30 degrees of flexion [Figure 2]. Such a position avoided overstretching of the synovial sac.
The measurement technique used to assess synovial thickness involved measurements of synovium at the suprapatellar, medial and lateral recesses taken in both the longitudinal and transverse planes. However the point localization, was done by marking the bony prominences around the knee joint and triangulating the site of measurement using these bony landmarks (tibial tuberosity and the joint lines) [Figure 3]. The distance from the three points helped in improving the accuracy of the study. No pressure was applied during the test process and a stand off pad of ultrasound coupling agent (gel) was used as the pressure the examiner applies would not be the same for every measurement or every patient. This would influence in the accuracy of the meausurement. The measurement included only the thickness of the synovium and not of the synovial fluid. The sum of these 3 measurements was taken as the total synovial thickening.
When the suprapatellar recess was examined, the ultrasonic probe was placed to get a longitudinal view. It was placed centrally and superiorly to the patella with tail end near the proximal top of the patella [Figure 4] and [Figure 7]. When the parapatellar medial and lateral recesses were examined the probe was placed at the medial transection of the patella in order to have a longitudinal view [Figure 5] and [Figure 6]. Throughtout the examination the probe was placed perpendicular to the skin surface and the thickest part of the synovium on the image was measured.
|Figure 4: Knee in neutral position with traducer position over the suprapatellar recess|
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|Figure 5: Knee in neutral position with traducer positioned over the medial recess|
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|Figure 6: Knee in neutral position with traducer position over the lateral recess|
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|Figure 7: Longitudinal section depicting the synovial thickening in suprapatellar pouch|
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The synovium was seen on HRUS as a hypoechoic structure distending the suprapatellar bursa. The synovium was seen to be echogenic, irregular and free floating within the synovial fluid. It was very susceptible to probe pressure and was easily flattened on flexing the knee. Occasionally we encountered few foci of calcification within it. No appreciable vascularity was noted on colour flow Doppler and power doppler settings. Maximum bulk of synovial tissue was seen in the region of the supra patellar bursa with synovium also extending to the right and left lateral recesses.
The adjacent bone was also examined for osteophytes [Figure 8], loose bodies, irregularities and also for meniscal cysts, popliteal cysts and integrity of adjacent ligaments and the infrapatellar bursa. The popliteal vessels were also examined.
12 sessions of 20 minutes of disc electrode SWD was given. The subjects were in a sitting position with the lower limb positioned comfortably on a stool at the front with ample support given to the thighs and the legs with the affected knee extended. The disc electrodes were placed around the knee joint in cross fire method. The intensity of the current was set based on each subject's sensation of warmth (a mild but pleasant sensation of heat). The 20 minutes was divided into 10 minutes at each of the 2 positions. And the total treatment time for the knee was 20 minutes.
The patient was instructed not to take any other treatment or take medication during the study period.
Before the therapy the ultrasonography images of all 20 participants were examined for synovial thickness, and pain index assessment also was undertaken. After the initial examination, SWD was given 3-5 times a week for a total of 12 treatment sessions within 3 weeks. Follow - up evaluation was performed on the day after the 4 th , 8 th and 12 th treatment sessions.
For each outcome variable, including both total synovial thickness and pain index, patient underwent measurements before the experiment and on the day of the 4 th , 8 th , and 12 th treatments, respectively. In addition, the difference in pain index for each measurement from the initial status was calculated and used for comparison of improvement in knee pain. Paired t test was used to compare pre and post intervention synovial thickness and pain.
| Results|| |
Twenty patients completed the entire series of examination with ultrasound evaluation at regular intervals (Pre, 4 th , 8 th and 12 th ).
For synovial thickness the pre treatment mean is 8.26 mm with SD (standard deviation) of 3.967 and post treatment mean is 6.56 mm with SD 3.842. This indicates that synovial thickness has decreased by 15.24%-20.58% after subjecting the patients to deep tissue heating [Table 2].
|Table 2: Effect of short wave diathermy on synovial thickness and pain relief|
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For pain relief pretreatment mean of NPRS value is 6.5 with SD of 1.491 and posttreatment mean is 3.7 with SD of 0.9718, which indicates that pain has decreased by 27% after giving treatment [Table 2].
Representative Case [Figure 9], [Figure 10], [Figure 11] and [Figure 12]
|Figure 9: Pretreatment synovial thickness in the medial recess of the right knee|
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|Figure 10: Synovial thickness after the 4th session of short wave diathermy|
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|Figure 11: Synovial thickness after the 8th session of short wave diathermy|
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|Figure 12: Synovial thickness after the 12th session of short wave diathermy|
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| Discussion|| |
The study protocol has been summarized in [Figure 13]. This study shows that ultrasonography is a useful tool to quantitatively detect changes in synovial thickness in the knee joint following SW diathermy therapy. The validity and reliability of data obtained with the ultrasonographic imaging technique which was used to determine the synovial sac thickness in patients with inflammation of the knee joint has been established in previous studies.
This study examines ultrasonographically detected changes in the synovial thickness in people with knee osteoarthritis after repetitive continuous short-wave diathermy. Although SW diathermy has been documented to improve the vascular circulation, there are very few studies showing change in synovial thickness (a sign indicating reduced synovitis) in response to this thermal effect. It was further ascertained that a sequential reduction in synovial thickness and knee pain could be obtained by repeated treatment sessions.
In the study carried out Mei-Hwa Jan et al.  the synovial sac thickness after 10 treatment sessions, reduced to 81%- 84% of the initial thickness; after 30 treatment sessions, it was approximately 67%-72% of the initial thickness. It also showed that there was no difference in synovial sac reduction with or without the use of NSAIDS. In our study the synovial sac thickness after 12 treatment sessions with no use of NSAIDS reduced to 79.42- 84.76 of its initial thickness.
In addition, the measured suprapatellar synovial thickness in patients with degenerative osteoarthritis in this study was 5.4 mm, which is slightly less than that measured by Rubaltelli and colleagues  in patients with rheumatoid arthritis (6.9 +/− 1.9 mm). This finding was consistent with the results of a histological study; that is, thickening of the synovial sac is less pronounced in degenerative osteoarthritis than in rheumatoid arthritis.  These findings are consistent with clinical presentation of synovitis and this further validates the use of ultrasonographic imaging in the measurement of synovial thickness.
In the studies by Karim et al.  and Van Holsbeeck et al.,  ultrasonographic imaging techniques were shown to yield valid and reliable data as well as more accurate data than clinical examination stand alone. Tsai et al.,  using different measurement protocol compared to the one used in our study (measured the synovial fluid and the synovial thickness), demonstrated high interrater and intrarater reliability of measurements of synovial thickness obtained with ultrasonography in patients with knee osteoarthritis.
Our study demonstrated a decrease in synovial thickening with increased treatment sessions in patients with knee osteoarthritis. As treatments were repeated, the synovium became thinner and the amount of pain experienced by patients became lower. The positive finding of SW diathermy is consistent with the results of previous studies that examined the therapeutic effects of SW diathermy. ,, This improvement in symptoms may be due to increased circulation around the knee joint and reduced synovial thickness, which became more evident after a series of SW diathermy treatments. The results of this study represent direct evidence of the effect of SW diathermy on synovial thickness.
Thus, it may be concluded that ultrasonographic imaging is a valuable objective tool in the evaluation of the severity and progression of synovitis.
In studies conducted by Hill et al.  the changes in synovitis was correlated with change in knee pain but not loss of cartilage, emphasizing the need to consider treatment of synovitis.
Pelletier et al.  concluded that MRI technology for assessment of synovial thickness in knee OA is accurate and reproducible. In studies conducted by Elka Miller  revealed that there is fair strength of evidence that MRI is an accurate diagnostic method for evaluating synovium and cartilage and for assessing clinical responsiveness to treatment in peripheral joints in Juvenile rheumatoid arthritis.
Limitations of our study are the small sample size, lack of control group and variability encountered in point localization for synovial thickness measurement.
Following 12 sessions of SW diathermy, although the reduction of the synovial thickness was significant, some participants still experienced some knee pain. We hypothesized that SW diathermy can reduce the synovial thickness, but that it might be not relieve patients' pain completely.
Further follow-up beyond the 12 th session needs to be done to further assess change in the synovial character and to ascertain the ultimate limit of synovial thickness reduction that can be attained. The comparison of HRUS with other imaging modalities like MRI to assess the synovial thickness can also be done. Also a comparison of B-mode and power doppler sonography and contrast enhanced musculoskeletal sonography can be done for detecting synovitis in knee osteoarthritis. Moreover studies to quantify synovial vascularization can be conducted by post contrast imaging.
| Conclusion|| |
Synovial thickness is a sensitive objective marker for articular damage and pain relief and has prognostic significance. There is a distinct role of HRUS in gauging response to short wave diathermy (SWD) in alleviation of symptoms.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13]
[Table 1], [Table 2]