Trial design
This single blind, randomized, and controlled trial, which conducted at Razi University rehabilitation center in Iran, lasting eight weeks between February 2019 and May 2019. The evaluators who measured variables for patients were blinded about the group allocation. This study included three steps: 1. Pre-tests 2. 8-week aquatic exercises and TRX exercises for case groups, and the control group was done just the rheumatologist advise 3. Post-tests (Fig 1).
Participants
Subjects of this research (200 female) were recruited by regular referral from rheumatologist physicians, and those patients who waited for common physiotherapy in rehabilitation centers.
Participants were included if they had (1) the age of more than 40 years old, (2) American College of Rheumatology clinical criteria for knee OA, (3) Kellgren and Lawrence radiographic disease severity scale ≥ II, and (4) self-reported knee instability. Additionally, all participants were excluded if they (1) had strokes, (2) had uncontrolled hypertension, (3) were unable to walk without assistant instruments, (4) had received other treatment interventions in past three mounts, (5) had obesity (BMI>40kg/m2), (6) suffered from neuromuscular diseases like MS and Parkinson, (7) had lower extremity fracture, (8) concurrent hip osteoarthritis, (9) waited for arthroplasty, and (10) had cardiovascular diseases. The knee in which they reported symptom of instability was assessed for all patients in this study [16]. The G.Power 3.1 software was used to estimate the minimum sample size. According to the results of previous researches and based on the test power of 0.90, the effect size of 0.63 and the significance level of 0.05, the minimum sample size was determined to be 36 [17]. Finally, they were divided randomly into three groups including TRX (n = 12), aquatic exercises (n = 12), and control (n = 12) groups (Table 2).
Study interventions
TRX exercises
The TRX ® Rip Trainer ™ (model) was used for the exercises performance. TRX training was completed by TRX specialist, and also all exercises were done by two trainers. the safety points were checked by trainer to avoid injuries, before the exercises started in every session. The TRX straps hanging down from the anchor point, and Suspension AnchorTM was adjustable to execute various exercises. Exercises were designed based on the patients’ motion limitations like knee flexion and extension. Furthermore, TRX exercises were started at the easiest forms, and going to be hard progressively. Intensity of exercises were step by step increased by 1) Narrowing the base of support 2) Changing the angle of pull 3) The pendulum, in which the feet were placed in the suspension trainer and the hands were off the ground, was used for ground exercises. The gravity center in relationship with the perpendicular gravitational pull determined the exercise intensity. 4) Using a one handle can increase the exercises difficulty. 5–10 min introducing the sessions’ exercises and their correct techniques, 5–10 min warm-up, which was stretching exercises, and also 40–50 min TRX exercises were performed per session. Participants who had wrist pain through the planks’ tests, could put their forearm on the ground in order to prevent the wrist pain increasing. The TRX exercises protocol were done for eight weeks, three times a week, and during 60 minutes for each session. Most of the exercises were focused on the core muscles, hip abductors, and leg muscles strengthening. TRX exercises were executed in three sections: the first section included all exercises which were performed in Sundays, the second section included all exercises which were performed in Mondays, and the third section included all exercises which were performed in Wednesdays for one month (Table 1) [18].
Table 1. insert here
Aquatic exercises
Aquatic exercises intervention was accomplished for eight weeks, three times a week, 24 sessions in total, and during 90 minutes for each session. The water temperature was approximately 32 ° C (89° F), and the water depth was considered as 1.3 meter. The water based exercises protocol included: 10 minutes’ warm-up along with walking (forward, backward, and sidewalk), and also stretching exercises for lower extremity muscles (quadriceps, hamstrings, triceps surae, abductors and adductors of hip, and gluteal muscles), 20-minute strength exercises with elastic band and sandbag (gluteus, adductors and abductors of hip, quadriceps, hamstrings, and triceps surae muscles); 20 minutes of aerobic exercises (stationary running or deep water-running); 20 minutes of step training and proprioceptive exercises; and 10 minutes of core exercises, and after that 10 minutes of cool down. we selected exercises based on studies for outcomes function, pain, balance [19, 20].
Randomization and Blinding
Participants were randomized by the use of Random Number Generator Software, and also were allocated to three groups using Sequentially Numbered Opaque Sealed Envelopes (SNOSE) concealed allocation method. A physiotherapist who did not involve in the data collection and evaluation of the outcomes has done random allocation sequence, enrolled participants and assigned participants to interventions. Participants were distributed to TRX (n = 12), aquatic exercises (n = 12), and also control groups (n = 12) by random (allocation ratio 1:1:1).
The assessors of this research were blinded about the exercises and interventions assigned to the groups, but there was no possible way for blinding the subjects to training as well as statistician towards the groups and their assigned exercises.
Study outcomes
We compared some variables such as (Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), pain, gait pattern, Berg balance scale (BBS), function, and quality of life (SF36) between subjects with and without self-reported knee instability before this research. We found that KI could effect on just four items like knee pain, WOMAC stiffness subscale, BBS [21], so we designed this research based on our results. We assessed the 8-week aquatic exercises, and TRX exercises effect on the affected factors by KI.
Knee pain
Knee pain intensity was measured by using 10-cm visual analog scale (VAS) with the scoring range between 0–10cm. “0” indicated the pain absence, “1” minimal pain, and “10” is extreme or intolerable pain. The participants were asked “how much pain do you have during your daily activities?” the VAS was used to measuring the intensity of participants’ subjective pain before and after the interventions. A good reliability and validity was reported for the VAS (intraclass correlation 0.92) [22].
WOMAC stiffness
WOMAC stiffness subscale had two items that were rated by the Likert scale of 0 (no symptoms)- 4 (extreme symptoms), with a total range of 0–8, and higher scores displaying worse symptoms [23].
Berg Balance Scale (BBS)
BBS, which was used to assessing the balance consists of 14 different tasks, was assessing balance in sitting and standing position and in transfer. Each motor task was rated by the use of 5-point scale ranged from 0 to 4. The total score ranges from 0 to 56, where 56 represents normal balance [24].
Knee instability
Self-reported knee instability was evaluated according to giving way, and also shifting evidence, during the last month by Felson’s questionnaire [25]. KI intensity was graded based on the numerical scale (0 to 5) in response to the following question “To what degree of giving way, buckling, or shifting of the knee would affect your daily routine activity?” The ratings were as followings: 5 = “I have no symptom”, 4 = “I have symptom, but it does not affect my ADL”, 3 = “Symptoms affect my ADL slightly”, 2 = “symptoms affect my ADL moderately”, 1 = “symptoms affect my ADL strongly”, 0 = “symptoms prevent me to perform all of my everyday activities” [25]. The test-retest reliability of this self-report rating of KI was estimated by the use of an intra-class correlation coefficient (ICC = 0.72) [26].
Ethical Considerations
This research’s protocols were reviewed and approved by the research ethics committee of the Medical Sciences University of Kermanshah in Iran (Registration no.: IR.UMMS.REC.1397.718). The study’s protocol was also registered in the Iranian Registry of Clinical Trials (Registration no.: IRCT20181222042070N1). The subjects provided informed consent forms, and all of the tests and measurements were carried out at the Sport Rehabilitation Laboratory of Razi University in Iran. As well, all of the patients completed the informed consent forms.
Statistical analysis
We analyzed BBS, Pain, WOMAC (stiffness), and self-report knee instability variables before and after the 8-week aqua therapy and TRX exercises.
At First, we used Shapiro-wilks and Leven’s test for assessing the normal distribution of data, and also the variances homogeneity. When variances normality and homogeneity tests were confirmed, the data were considered to be parametric. Consequently, the dependent variables’ mean comparisons amongst the groups were made by the one-way analysis of variance (ANOVA), and also Tukey’s post hoc test was used for the pairwise comparisons. The effect size (ES) calculated by ES [Due to technical limitations, this equation is only available as a download in the supplemental files section.] sum of squares between groupssum of squares total. The guidelines for interpreting this value included small effect = 0.01, moderate effect = 0.06, and great effect = 0.14 [27]. The 5% was considered as significant level. All results were reported as the mean ± standard deviation. SPSS software was used to data analysis (SPSS Inc., Chicago, IL; version 22). In addition, statistical significant level was considered 0.05.