Sample size
A power analysis indicated that a sample size of 45
patients would provide 80% power at an alpha level of
0.05 (effect size: 0.506).
Patient population
Fiftyfive patients, who admitted with knee pain lasted
for at least 3 months were evaluated. Patients were assessed by one of the two authors by history and
detailed physical examination. Laboratory tests (whole
blood count, C-reactive protein, erythrocyte sedimentation
rate, rheumatoid factor and routine biochemical
tests) were assessed to rule out secondary OA. All patients
were initially questioned for age, sex, weight and height.
The diagnosis of KOA was based on the American Collage
of Rheumatology criteria20. Patients who had not
responded adequately to treatment with nonsteroidal
anti-inflammatory drugs, had grade II-III Kellgren-
Lawrence21 scores and had no limitation in range of
motion were included to the study. Exclusion criteria
were as follows: 1.secondary OA, 2. contraindications for
PEMF and US therapy such as tuberculosis, pregnancy,
malignancy, cardiac pacemaker or any implanted electrical
device, atrophic skin or scar tissue on the knee region,
bleeding disorders, insensitivity, edema and ischemia, 3.
unable to understand the questionnaires. Furthermore
patients were excluded from the study if they had been
on pyhsical therapy programme or had recieved intraarticular
injections in the previous 6 months, had undergone
an operation for any knee pathology previously.
Eight patients were excluded from the study. Two patients
did not participate because of inconsiderable reasons so
45 patients completed the study. All participants gave
written informed constant. The study was approved by
the ethics commitee of the university.
Randomization
Patients were randomly allocated to three groups by
sequential assignment, according to their application turns.
First group (1st, 4th, ...43rd) recieved PEMF therapy, second
group (2nd, 5th, ...44th) recieved US therapy, third group (3rd,
6th, ...45th) recieved no treatment. Figure 1 shows the randomization
and follow-up process of the groups. Neither
the assessors nor the patients were blinded.
Therapy protocols: PEMF group
PEMF therapy was applied by a magnetotherapy device
(BodyMag, manufactured by Eltech S.r.l, Treviso, Italy). Both
knee of the patients were put in the middle portion of the
big cycle solenoid applicator in supine position. The frequency, intensity and application duration/session were
selected according to the recommendations of the manufacturer.
PEMF was applied in a frequency of 2 Hz, 100 Hz
and 25 Hz, consecutively. Intensity variated between 2mT
and 10 mT during the application. A therapy session lasted
for 35 minutes and 15 sessions performed during 3 weeks (5
sessions/week).
US therapy group
The skin was coated with an acoustic gel not containing
any pharmacologically active substance. US was then
applied to the superomedial and lateral parts of the knee
by the same therapist stroking the applicator in circular
movements. The transducer head was applied to the knee
at right angles to sustain maximal absorption of the ultrasound
energy. Continuous ultrasonic waves with 1 MHz
frequency and 1.5 watt/cm2 power were applied with a 3
cm diameter applicator ultrasound equipment
(Chattanooga, TN, USA.). US therapy lasted for 10 minutes/
session.
Third group served as control. Only the third group
was allowed to receive paracetamol when needed during
the study.
Outcome measures
Severity of joint pain, joint stiffness and physical function
levels were evaluated as outcome measures.
Assessment tools were Visual Analoge Scale (VAS) (from
no pain=0 to unbearable pain=10) and Western Ontario
and McMaster Universities (WOMAC) questionnaire.
WOMAC is a validated, disease specific and sensitive measurement
of symptom related to KOA22. It has 3 parts
which measures pain, stiffness and physical function. The
validity of Turkish version of WOMAC questionnaire has
been well documented23. WOMAC scores were recorded
on a Likert scale of 0 -4, where 0= no pain/ limitation
and 4=very severe pain/limitation. Maximum scores for
stiffness, pain and physical function were 8, 20 and 68
respectively.
Statistical analysis
Statistical tests were performed by SPSS program (version
11.0). All data was expressed as mean±standard deviation or median (minimum-maximum). Demographic
characteristics were compared by χ2 test and ANOVA.
Kruskal Wallis test was used in order to compare the differences
between changes of scores during time among
the groups. For the significant differences according to
Kruskal Wallis variance analysis, Mann-Whitney U test
was used to analyze which group is different from the
other in terms of those parameters. Bonferroni correction
was applied for all possible multiple comparisons.
Differences within groups were analyzed by Wilcoxon
signed rank test.
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