This was a longitudinal cohort study. The study duration for data collection was 12 months, April 2019 to April 2020. Chit method in simple random sampling method was used. IEC approval was done by the Institutional ethical committee (Ref No. KIPT/31/19-20 Dated 23/04/2019.) and informed consent was signed by all the patients participated in the study.

Inclusion criteria: Patients suffering with chronic knee osteoarthritis for at least six months, age group between 50-65 years, both male and female subjects, bilateral chronic knee osteoarthritis, X-ray: showing osteophytes, joint space narrowing at the knee joint Kellegren Lawrence Grade 2 and Grade 3 [18].

Exclusion criteria: Acute and sub-acute bilateral knee osteoarthritis patients, any old fracture at knee joint, ankylosing spondylitis, any previous knee pathology, any previous knee surgery; any post-surgical implant fixation at the knee region, tumours and cancer, any peripheral nerve lesions, any cardiopulmonary and renal condition.

Pain status, Range of Motion and Disability were measured by using Visual Analogue Scale, Universal Goniometer, Short Form-36 Health Status Questionnaire and WOMAC Arthritis Index Questionnaire. SF-36 Health status questionnaire and WOMAC Arthritis Index Questionnaire are available as a free tool on the internet and the scales were not modified by the researcher in the present study. The outcome measures were taken on the day before commencing the treatment, at the end of the 2^nd week and finally at the end of the 4^th week after the treatment.

The study was a hospital center based comparative follow up from day 1 to week 4. Sample for the study comprised of 90 chronic knee osteoarthritis patients aged between 50 to 65 selected by simple random sampling method. Samples of the study comprised of bilateral chronic knee osteoarthritis patients at Kempegowda Institute of Medical Sciences. The study was conducted, and outcome measures (VAS range of motion disability) were collected on day 1, at the end of 2^nd week and at the end of 4^th week. The study samples were selected based on inclusion and exclusion criteria. The 90 chronic knee osteoarthritis patients were divided into two groups having 45 samples in each group, group A patients were given contrast bath and knee exercises and were instructed to fill the Short Form – 36 Questionnaire on day 1, at the end of 2^nd week and at the end of 4^th week and group B patients were given contrast bath and knee exercises and were instructed to fill WOMAC Arthritis Index Questionnaire on day 1, at the end of 2^nd week and at the end of 4^th week.

In this study all the 90 subjects underwent exercise program as follows from 1^st day to 4^th week:

The subjects were also given contrast bath on bilateral knee through packs of layers of towels. The total treatment time was 21 minutes which consist of four minutes of warm, followed by one minute of no treatment and then two minutes of cold. This cycle was repeated three times, in a total session of 21 minutes. All the subjects were given physiotherapy treatment for five visits per week for four weeks. The range of motion of right and left knee of all the 90 subjects was measured using a goniometer on day 1, end of the 2^nd week and end of the 4^th week.

Data were analysed using the Statistical Package for Social Science (SPSS) version 19.0 (Chicago, IL) and level of significance was set at p<0.05. Descriptive statistics was performed to find out the mean and standard deviation of the respective groups. Normality of the test was assessed using Shapiro Wilkins test. ANOVA test followed by Post-hoc analysis was used within the groups to find out the statistical significance. Independent t-test was used between the groups to find out the significance.

Group A patients had a mean of 58.17 (SD 3.66). Group B patients had a mean of 58.15 (SD 4.29). Group A and Group B are almost similar with respect to the age of the participants. T-test shows significance between the groups and hence, the groups are comparable (p>0.05) [Table/Fig-1].

Group A contains of 73.3% of females (33) and 26.7% of males (12). Group B participants are 57.8% females (26) and 42.2% of females (19) [Table/Fig-2].

Statistical analysis using Independent t-test between the groups showed significant difference of improvement at day 1, week 2 and week 4 in both the groups (p<0.041) [Table/Fig-3].

Statistical analysis using ANOVA and Post-hoc test between groups showed significant improvement in range of motion of right knee at day 1, week 2 and week 4 in group A and group B (p<0.046). Post-hoc analysis also showed significant difference at all pair group comparison (p<0.05) in both group A and group B.

The percentage improvement of range of motion in right knee joint showed a better improvement with respect to Group B (28.4% vs 22.8%) compared to Group A [Table/Fig-4].

Statistical analysis using ANOVA and Post-hoc test between groups showed significant improvement in range of motion of left knee at day 1, week 2 and week 4 in group A and group B (p<0.05). Post-hoc analysis also showed significant difference at all pair group comparison (p<0.05) in both group A and group B.

The percentage improvement of range of motion in left knee joint showed a better improvement with respect to Group B (23.1% vs 18.3%) compared to Group A [Table/Fig-5].

Group A shows a mean and the standard deviation of the total score of the Short Form-36 Questionnaire which was 88.24 (SD 6.27) on day 1; mean of 94.06 (SD 5.10) at the end of week 2 and a mean of 98.73 (SD 4.55) at the end of week 4. Statistical analysis using Independent t test within the group showed significant improvement at day 1, week 2 and week 4. Within group analysis using ANOVA followed by Post-Hoc test showed significant improvement at day 1, week 2 and week 4 [Table/Fig-6].

It shows a mean of 78 (SD 10) on day 1; mean of 51 (SD 12) at the end of week 2 and a mean of 22 (SD 13) at the end of week 4.

Statistical analysis using Independent t-test within the group showed significant difference of improvement at Day 1, Week 2 and Week 4 (p<0.05).

Within group analysis using ANOVA followed by Post-hoc Test showed significant improvement at day 1, week 2 and week 4 (p<0.05) in Group B [Table/Fig-7].

Statistical analysis using Independent t-test between the groups showed no significant difference of improvement at day 1, week 2 and week 4 intervals (p>0.05) [Table/Fig-8].

At the beginning, 145 patients were evaluated for eligibility to enter the study. Finally, 90 patients (for both WOMAC and SF-36) were included in the study. The study population, characteristics, samples, age, gender and range of motion were consistent with the study which showed that there was a specific importance of contrast bath and knee exercises, which when implemented on patients showed significant improvement in the score of WOMAC questionnaire and SF-36. In present study, null hypothesis was rejected, and alternate hypothesis was accepted.

The mean age in the Group A was 58.17 and Group B was 58.15. The standard deviation of group A was 3.66 and group B was 4.29. Further, the present study was supported by Xie Y et al., who conducted a systematic review in 2018, which also had patients with the age group of above 50 years [18].

The present study showed significant improvement in VAS between Day 1-Week 4 (p<0.05) in group B compared to group A patients. The effectiveness of reducing knee pain was supported by Shehata AE and Fareed ME, which conducted a study in 2018 who concluded that contrast bath appears effective in treating chronic knee osteoarthritis patients [19]. Further the effectiveness of exercises in treating chronic knee osteoarthritis patients was supported by Deyle GD et al., who concluded that exercise yields functional benefits for patients with chronic knee osteoarthritis and may delay or prevent the need for surgical intervention [20].

The WOMAC Arthritis Index is a disease specific measure of disability associated with knee osteoarthritis that has demonstrated well to excellent reliability and validity. It is a 24 items questionnaire focusing on pain, stiffness and functional limitation. A higher score indicates worse pain, stiffness and physical function.

On the other hand, Short Form-36 is used to examine health status in the following 8 domains: bodily pain, physical function, role limitations due to social problems, physical problems, general health, vitality, social function, mental health, role limitation due to physical problems. The items contributing to a scale are scored so that a higher score represents better health, and they are averaged together to create the scale score. As both the scales are designed to evaluate disability and the quality of life, the researcher had chosen these two scales in the present study.

The within group analysis of SF-36 showed significant improvement between day 1 and week 4 (p<0.05). The use of SF-36 Questionnaire was supported by Laucis NC et al., at Los Angeles, CA, in 2015 who had concluded that SF-36 and its various versions are currently the most widely used health related Quality of Life measures in the United States [21]. This study was also supported by Srivastava SR who concluded that SF-36 is the gold standard to assess quality of life of people with knee osteoarthritis [22].

The present study showed that there is significant improvement in the scores of the WOMAC Arthritis Index Scale and its percent disability between the day 1 and week 4 (p<0.5) in group B patients. Further, this was supported by Basaran S et al., which conducted a study at Turkey, in the year 2010 where the researcher had reviewed various studies in which the WOMAC Arthritis Index Questionnaire was used as a valid tool [23].

Raeissadat SA et al., 2017 in his study concluded that there is a positive correlation between WOMAC and SF-36 in measuring health related quality of life in patients with knee osteoarthritis [24]. Previous evaluations of measurement characteristics of WOMAC and SF-36 in knee osteoarthritis patients have been done following joint replacement surgeries [25-28]. In such research, WOMAC performed better. In this study, while both WOMAC and SF-36 responded positively to the treatment, however, degree of responsiveness in WOMAC was far greater than SF-36. In line with the decrease in VAS scores, SF-36 also showed improvement, however, the degree of improvement was not so significant as compared to WOMAC. This was clearly demonstrated by rapid responsiveness and greater sustained increase in WOMAC scores following the commencement of treatment. SF-36 scores also reflected improvement but were not relatively rapid. This is because of the following key reasons: (a) The recall period in SF-36 is of one week. This is not a problem for WOMAC as the recall time is limited to 48 hours; (b) SF-36 is a generic health status instrument which is generally used to assess the social, mental and physical construct. Conceptually, improvement in physical construct could leads to social and mental improvements in future. However, the outcome measurements of such improvements cannot be assessed in short period. It is possible that the duration of the study was less to detect much improvement is SF-36 scores; (c) The lack of response in SF-36 scale may be due to lack of adequate and appropriate response categories for chronic knee osteoarthritis patients; (d) WOMAC on the other hand is a core functional assessment tool which eliminates some of the social and mental assessment outcomes in the treatment, thereby, leading to high responsiveness towards physical/functional assessment in chronic knee osteoarthritis patients.

From this study, it appears that WOMAC is more efficient than SF-36 in treatment of chronic knee osteoarthritis patients using contrast bath and knee exercises.

The study population was small. No long term follow up. The age group of patients limits the study. The frequency of male and female subjects was not equally distributed.

The present study showed significant differences in the outcome measures of range of motion and also the visual analogue scale in Group A and Group B. There was significant difference in the pre and post total scores of Short Form-36 Questionnaire of Group A patients as well as significant differences in the pre and post total scores in the WOMAC Arthritis Index Questionnaire and its percent disability score. The present study also shows that the WOMAC Arthritis Index Questionnaire has shown superior sensitivity in the percentage wise improvement in the chronic knee osteoarthritis patients than the Short Form-36 Questionnaire.