Abstract
Objective
To assess the level of scientific evidence and the place in the rehabilitation framework of isokinetic muscle strengthening (IMS) for knee osteoarthritis (OA).
Methods
A systematic review of the English literature in MEDLINE via PubMed, the Cochrane Library, and PEDro databases for only randomized comparative trials. Data that were sufficiently homogeneous underwent comprehensive meta-analysis. Methodological assessment was done by using the CLEAR scale for non-pharmacologic trials.
Results
We identified articles for 9 trials (696 patients). All trials were of low to moderate quality. Tolerance of IMS was considered good. Improvement in muscle strength was better with an IMS program than no treatment or an isometric exercise but did not differ with an aerobic program. We found an important effect for pain (standardized mean difference 1.218 [95% CI 0.899–1.54], P < 0.001) and functional Lequesne index (1.61 [0.40–2.81], P = 0.009) and a moderate effect for the Western Ontario and McMaster Universities Osteoarthritis Index subscore C for disability (0.58 [0.04–1.11], P = 0.03).
Conclusions
IMS is an effective way to propose dynamic muscle strengthening for knee OA rehabilitation and has a significant effect on pain and disability. Because of the weak methodology and the great heterogeneity of studies, particularly in IMS protocol and outcome measures, insufficient data are available to provide guidelines about efficacy and strategy. Future clinical trials are needed, but more attention should be paid to the methods of such studies to clarify the role of IMS in the therapeutic armamentarium of knee OA.
1
Introduction
Because of the aging of the population, osteoarthritis (OA) is a major public health problem. OA is one of the 10 most incapacitating diseases in developed countries. Worldwide, 9.6% of men and 18% of women have OA . The disease limits motion for 80% of patients, and 25% are restricted in activities of daily living . These disabilities, mostly due to the pain , are detected by limitations in walking, climbing stairs, doing household chores or getting up from sitting . They are associated with reduced health-related quality-of-life and have important psychological impact.
Despite advances in research and some promising new therapies, no treatment can prevent or cure OA. However, disease-related factors, such as impaired muscle function and reduced fitness, could be amenable to exercise . International guidelines advocate various nonpharmacological treatments (NPTs), including exercise, for first-line management of OA .
Types of exercise regimens found effective in controlling pain and maintaining function in knee OA include aerobic exercise and strength training . Even simple aerobic walking can reduce pain and improve function. Strength training programs have included various forms of isometric and dynamic exercise, the latter involving resistance training with elastic bands and isokinetic dynamometers. Resistance or strength training also has positive effects on pain and functional outcomes for knee OA . Both home- and gym therapy-based resistance training appears to be effective, and patient preference, education, and access should be considered when developing a plan of care . Under most recent guidelines, OA treatment must centre on nonpharmacological therapy . These international guidelines highlight the importance of exercise therapy and especially muscle-strengthening for knee OA as well as personalizing the physical exercise that can improve walking, ameliorate pain or aid in activities of daily living .
Quadriceps weakness is frequently found in early knee OA, stage 0 or 1 Kellgren and Lawrence radiographic classification, even if patients do not have knee pain or muscle atrophy. If the patient has knee pain, this weakness seems to be strongly associated with the pain and the level of disability . The weakness may be caused by muscle dysfunction and may be a risk factor for OA progression . Strengthening the quadriceps and hamstrings helps maintain and increase strength, joint stability and mobility, allowing for better range of motion (ROM) in flexion and extension movements and better tolerance of pain .
In addition to being related to pain and limitation in functional capacity, muscle weakness affects the progression of OA . Severe levels of disability or inactivity induce muscle wasting and may contribute to the decline in strength reported by older people . These findings may have important implications for people with knee OA and knee pain, particularly with a therapeutic and preventative role of increased muscle strength reducing or stopping disease progression. The literature confirms that exercises, particularly strengthening exercises are beneficial in improving physical function and strength in people with knee OA . However, which type of strengthening exercise could have the best impact on functional outcomes is unclear.
Several high-quality reviews of exercise therapy in OA are available, but they do not make a clear distinction between modalities of exercise . Isokinetic exercise is a mode of speed-constant training. The velocity of the joint motion is constant, excluding acceleration to and deceleration from the designated speed, and the force depends on how hard the individual pushes against the load cell. The exercise can be used at low, moderate and high velocity for different evaluations and rehabilitation programs and provides reliable data. Isokinetic exercise is actually used to quantify muscle strength, treatment and rehabilitation efficacy with mechanical or neurological instability of the knee or ligament injury . Moreover, isokinetic exercises can be used as personalized muscle-strengthening techniques, offering a graduated and secure program, with an objective measure of the progress. The exercise offers great selectivity for the motion required in ambulation and produces a faster rate of strength gain and reduced muscle tenderness than isotonic training . Also, increases in heart rate and blood pressure seem to be lower with isokinetic than isometric exercise, which could be of particular importance among older patients with OA who often have comorbidities .
Our objectives were to:
- •
systematically review results from randomized controlled trials (RCTs) of isokinetic muscle-strengthening (IMS) interventions in cohorts with knee OA;
- •
evaluate the evidence for the effect of IMS on pain, disability and walking with meta-analysis if possible.
2
Methods
2.1
Selection of articles
Two reviewers (EC, JPM) searched and selected articles independently according to the PRISMA guidelines . We searched via PubMed, Cochrane Library and PEDro databases using the keywords “knee” “osteoarthritis”, “isokinetic” “Muscle Strength Dynamometer”, “rehabilitation”, “randomized controlled trials” for articles about patients with knee OA that had a summary and were published in English from 1966 to November 2015. Duplicates were removed after all databases were searched. We included full-length articles of RCTs investigating patients with knee OA and isokinetic exercise interventions and excluded reports of studies including patients with secondary knee OA (traumatic or postsurgical) or surgical end stage knee OA or that did not use isokinetic exercise therapy or used isokinetic dynamometers for strength assessment. We excluded studies without an abstract and case reports. For articles referring to isokinetic devices as treatment for knee OA, we excluded studies that did not include physical therapy or did not include a nonexercise control group. We retained only articles of RCTs in which treatment with isokinetic exercise was compared to another treatment or to no intervention.
2.2
Methodological quality assessment
The analysis of methodological quality involved the CheckList to Evaluate A Report (CLEAR) scale, which includes the most decisive methodological elements to validate the results of NPTs . Two readers (EC, JPM) independently evaluated each article and resolved any disagreements by consensus.
2.3
Statistical analysis
The various outcome measures were classified as objective or subjective (patient-reported) evaluation. Statistical analysis involved use of Comprehensive Meta-analysis v2 (Biostat Corp.), when appropriate (sufficient data available). Analysis of standardised mean differences (SMDs) and 95% confidence intervals (95% CIs) involved random-effects models assuming between- and within-study variability (DerSimonian and Laird approach). Statistical heterogeneity between results was assessed by examining forest plots, CIs and the I 2 statistic, the most common metric for measuring the magnitude of between-study heterogeneity and easily interpretable. I 2 values range from 0% to 100% and are typically considered low at < 25%, modest at 25–50%, and high at > 50%. This statistical method generally assumes heterogeneity with P < 0.05 for the I 2 test. Publication bias was assessed by the Egger test and represented graphically by funnel plots of the standard difference in means versus the standard error; P < 0.10 was considered statistically significant. The Trim and Fill analysis for publication bias involved the Duval and Tweedie method; P < 0.05 was considered statistically significant in all analyses. A sensitivity analysis was conducted to assess the effect of including and excluding studies on the global SMD.
2
Methods
2.1
Selection of articles
Two reviewers (EC, JPM) searched and selected articles independently according to the PRISMA guidelines . We searched via PubMed, Cochrane Library and PEDro databases using the keywords “knee” “osteoarthritis”, “isokinetic” “Muscle Strength Dynamometer”, “rehabilitation”, “randomized controlled trials” for articles about patients with knee OA that had a summary and were published in English from 1966 to November 2015. Duplicates were removed after all databases were searched. We included full-length articles of RCTs investigating patients with knee OA and isokinetic exercise interventions and excluded reports of studies including patients with secondary knee OA (traumatic or postsurgical) or surgical end stage knee OA or that did not use isokinetic exercise therapy or used isokinetic dynamometers for strength assessment. We excluded studies without an abstract and case reports. For articles referring to isokinetic devices as treatment for knee OA, we excluded studies that did not include physical therapy or did not include a nonexercise control group. We retained only articles of RCTs in which treatment with isokinetic exercise was compared to another treatment or to no intervention.
2.2
Methodological quality assessment
The analysis of methodological quality involved the CheckList to Evaluate A Report (CLEAR) scale, which includes the most decisive methodological elements to validate the results of NPTs . Two readers (EC, JPM) independently evaluated each article and resolved any disagreements by consensus.
2.3
Statistical analysis
The various outcome measures were classified as objective or subjective (patient-reported) evaluation. Statistical analysis involved use of Comprehensive Meta-analysis v2 (Biostat Corp.), when appropriate (sufficient data available). Analysis of standardised mean differences (SMDs) and 95% confidence intervals (95% CIs) involved random-effects models assuming between- and within-study variability (DerSimonian and Laird approach). Statistical heterogeneity between results was assessed by examining forest plots, CIs and the I 2 statistic, the most common metric for measuring the magnitude of between-study heterogeneity and easily interpretable. I 2 values range from 0% to 100% and are typically considered low at < 25%, modest at 25–50%, and high at > 50%. This statistical method generally assumes heterogeneity with P < 0.05 for the I 2 test. Publication bias was assessed by the Egger test and represented graphically by funnel plots of the standard difference in means versus the standard error; P < 0.10 was considered statistically significant. The Trim and Fill analysis for publication bias involved the Duval and Tweedie method; P < 0.05 was considered statistically significant in all analyses. A sensitivity analysis was conducted to assess the effect of including and excluding studies on the global SMD.
3
Results
3.1
Selection of articles
The selection of articles is in Fig. 1 . The database search resulted in 198 articles. Finally, we selected 11 articles about IMS as a therapeutic tool for knee OA. We eliminated 1 trial about a case report and 1 prospective non-randomized trial with doubt as to the real use of an isokinetic device , for 9 reports of trials involving 696 patients . Five trials compared IMS to a control group without an intervention, 5 compared IMS to another method of muscle reinforcement, and 1 compared 2 methods of IMS, concentric and concentric-eccentric combined ( Table 1 ).
| Author | Study Population Effective | Intervention | Follow-up length | Isokinetic exercises |
|---|---|---|---|---|
| Eyigor, 2003 | 44 patients; Stages 2 and 3 Knee OA according to KL | Gr 1: IMS Gr 2: Isotonic ex: PRE 5 days/week | 6 weeks of treatment and follow-up | 18 sessions: 3 sessions per week for 6 weeks Both knees treated IMS: Max effort on 3 sets of 6 E at 60, 90,120 and 180°/s 20 sec of rest between 2 sets |
| Gür et al., 2002 | 23 patients; Stages 2 and 3 Knee OA according to KL | Gr 1: Conc IMS Gr 2: Conc and Ecc IMS Gr 3: control group | 24 sessions; 8 weeks of treatment and follow-up | 24 sessions: 3 sessions per week for 8 weeks Both knees treated Gr 1: 12 repetitions in Conc, in E and in F at 30°, 90°, 120°, 150° and 180°/s Gr 2: 6 repetitions in Conc, then 6 repetitions in Ecc, in E and F, at 30, 60, 90,120, 150 and 180°/s 2 min of rest between E and F; 5 min of rest between left and right legs |
| Huang et al., 2003 | 132 patients; Stage 2 Knee OA according to Altman | Gr 1: IMS Gr 2: isotonic ex Gr 3: isometric ex Gr 4: control group | 8 weeks of treatment 1 year follow-up | 24 sessions: 3 sessions per week for 8 weeks Both knees treated IMS: ex at 60% of the average peak torque Number of sets increasing on the 5 first sessions (from 1 to 5 sets) From the 6th to the 24th session: 6 sets per session Each set: 5 repetitions in Conc/Ecc in F, then in E at 30° and 120°/s 5 sec rest between sets, 10 s between modes, 10 min between left and right legs |
| Huang et al., 2005 | 140 patients; Stage 2 Knee OA according to Altman | Gr 1: IMS Gr 2: IMS + PUS Gr 3: IMS +PUS+HAI Gr 4: group control | 8 weeks of treatment 1 year follow-up | |
| Huang et al., 2005 | 120 patients; Stage 2 Knee OA according to Altman | Gr 1: IMS Gr 2: IMS + CUS Gr 3 IMS + PUS Gr 4: control group | 8 weeks of treatment 1 year follow-up | |
| Maurer et al., 1999 | 113 patients; Stages 1 and 3 Knee OA according to KL | Gr 1: IMS Gr 2: Educational program | 8 weeks of treatment 12 weeks follow-up | 24 sessions: 3 sessions per week Affected knee treated Each session: 3 sets of 3 E at 90°, 120° and 150°/s 1 min rest between sets |
| Samut et al., 2015 | 42 patients, Stages 2 to 3 Knee OA according to KL | Gr 1: IMS Gr 2: Aerobic Gr 3: control group | 6 weeks of treatment and follow-up | 18 sessions: 3 sessions per week Both knee treated 5 repetitions F/E at each angle (60°, 90°, 120°, 180°/s) 1 set of contraction in the 1st session, increase to 6 sets by 1 increament in each following session and continued as 6 sets until the end of the study |
| Schilke et al., 1996 | 20 patients; Knee OA | Gr 1: IMS Gr 2: control group | 8 weeks of treatment and follow-up | 24 sessions: 3 sessions per week Both knees treated Number of sets increasing from 1 to 5 sets on the 5 first sessions From the 6th to the 24th session: 6 sets per session Each set: 5 contractions at 90°/s 1 min rest between sets; 15 min between sets 3 and 4 |
| Tuzun et al., 2004 | 62 patients; Stages 1 to 3 Knee OA according to KL | Gr 1: IMS Gr 2: Isotonic ex | 8 weeks of treatment 3 months follow-up | 40 sessions: 5 sessions per week Both knees treated 10 repetitions F/E at each angle (60°, 90°, 120°, 180°/s) |
3.2
Assessment of the methodological quality of studies
Table 2 summarizes the internal validity of the selected studies, which provides information in addition to the cause and effect of the observed modifications and the elected treatment. We selected 7 items from the CLEAR scale for evaluation. Because therapists’ experience cannot be used as evaluation criteria, with isokinetic evaluation used as a device, the intervention of the therapist does not interfere with the isokinetic evaluation, so we used “unclear” for this item, as recommended by the Delphi consensus . Patients and therapists could not be blinded to the isokinetic technique, as measured by items 6 and 7 of the CLEAR NPT, so we used the response “no” for these 2 items (results not shown) ( Table 2 ). Of the 9 studies, 3 met 4 of the 7 items of the CLEAR NPT scale; 4 met 3 items and 2 met 2 items.
| Author | Adequate allocation sequence | Was the treatment allocation concealed | Description of the interventions | Adherence of the participants | Primary outcome assessors adequately blinded | Identical planning between the groups | Intent-to-treat |
|---|---|---|---|---|---|---|---|
| Eyigor, 2003 | U | U | Y | N | Y | Y | N |
| Gür et al., 2002 | U | U | Y | Y | U | Y | N |
| Huang et al., 2003 | U | Y | Y | Y | U | Y | N |
| Huang et al., 2005 | U | Y | Y | Y | U | Y | N |
| Huang et al., 2003 | U | Y | Y | Y | U | Y | N |
| Maurer et al., 1999 | U | U | Y | N | Y | Y | N |
| Samut et al., 2015 | U | U | Y | N | Y | Y | N |
| Schilke et al., 1996 | Y | N | Y | N | U | Y | N |
| Tuzun et al., 2004 | U | U | Y | N | U | Y | N |
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