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Keywords:

  • Osteoarthritis;
  • Physiotherapy;
  • Exercise therapy;
  • Booster sessions;
  • Systematic review;
  • Long-term effectiveness

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information

Objective

To determine the long-term effectiveness (≥6 months after treatment) of exercise therapy on pain, physical function, and patient global assessment of effectiveness in patients with osteoarthritis (OA) of the hip and/or knee.

Methods

We conducted an extensive literature search in PubMed, EMBase, CINAHL, SciSearch, PEDro, and the Cochrane Central Register of Controlled Trials. Both randomized clinical trials and controlled clinical trials on the long-term effectiveness of exercise therapy were included. The followup assessments were at least 6 months after treatment ended. Methodologic quality was independently assessed by 2 reviewers. Effect estimates were calculated and a best evidence synthesis was performed based on design, methodologic quality, and statistical significance of findings.

Results

Five high-quality and 6 low-quality randomized clinical trials were included. Strong evidence was found for no long-term effectiveness on pain and self-reported physical function, moderate evidence for long-term effectiveness on patient global assessment of effectiveness, and conflicting evidence for observed physical function. For exercise programs with additional booster sessions, moderate evidence was found for long-term effectiveness on pain, self-reported physical function, and observed physical function.

Conclusion

The positive posttreatment effects of exercise therapy on pain and physical function in patients with OA of the hip and/or knee are not sustained in the long term. Long-term effectiveness was only found for patient global assessment of effectiveness. However, additional booster sessions after the treatment period positively influenced maintenance of beneficial posttreatment effects on pain and physical function in the long term.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information

Osteoarthritis (OA) is a relatively common musculoskeletal disorder, with a high prevalence that increases with age (1). OA can occur in any joint but appears most frequently in the knee and hip joints. OA causes pain and impairment in body functions such as muscle strength, range of joint motion, and joint stability. Furthermore, OA has a major impact on physical functioning in daily life and frequently leads to moderate to severe limitations in participation and a decreased quality of life (2–4).

Therapeutic exercise is recommended in several recent treatment guidelines for patients with OA of the hip or knee (5–8). A lack of regular physical activity is a risk factor for functional decline and is associated with increased health care costs (9). Exercise therapy aims to improve patients' overall function and to help them meet the demands of daily living. It can be defined as a range of activities involving the prescription of muscular contraction and bodily movement (10). Exercise therapy is a general concept that can be delivered in many ways. For instance, exercise therapy can differ in content (e.g., muscle strengthening exercises, functional task-oriented exercises), dosage (e.g., frequency, intensity, duration), and delivery mode (e.g., individualized, group based, home based). Physiotherapists choose the delivery mode, content, and dosage of exercise therapy based on their clinical decision-making process (11, 12).

Several systematic reviews outline the effectiveness of exercise therapy in the OA population (13–16). These reviews conclude that exercise therapy has beneficial effects on pain, physical function, and patient global assessment of effectiveness. However, most of these studies focus on short-term results, ignoring long-term effects (15, 16). Because OA of the hip and/or knee is a progressive disease and patients have to cope with their disease and its functional consequences for the rest of their lives, it is important that beneficial posttreatment results are sustained in the long term.

Since the publication of the reviews mentioned above, several new randomized clinical trials of exercise therapy in patients with OA have been published. Some of these trials focused on the long-term effectiveness of exercise therapy. Therefore, the objective of this systematic review was to determine the long-term effectiveness of exercise therapy in patients with OA of the hip and/or knee.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information

Long-term effectiveness was defined as the effectiveness of exercise therapy ≥6 months after the treatment period ended. Additional booster sessions in the posttreatment period were allowed if they consisted of either strategies that supported and/or stimulated long-term adherence to exercise, or advice about physical activities and/or integration of exercise in patients' daily lives. Studies investigating exercise therapy that included additional posttreatment booster sessions were reported separately from studies investigating the long-term effectiveness of traditional exercise interventions.

Search strategy.

Following the recommendations of the Cochrane collaboration, an extensive computerized literature search was conducted in several databases: PubMed (using articles published from 1966 to November 2005), CINAHL (1982 to November 2005), EMBase (1988 to November 2005), SciSearch (1974 to November 2005), Cochrane Controlled Trial Register (November 2005), PEDro (1929 to November 2005), and the library databases of medical and rehabilitation literature of 2 Dutch institutes (Dutch National Institute Allied Health Professions and Netherlands Institute for Health Services Research). The computerized search was built upon the following components: 1) a search strategy for controlled clinical trials and randomized controlled trials following the recommendations of the Cochrane Musculoskeletal Group (17); 2) a search strategy for the identification of studies involving patients with OA using the key words and free text words “osteoarthritis,” “osteoarthritis, hip,” “osteoarthritis, knee”; and 3) a search strategy for the identification of studies involving exercise therapy interventions using the key words and free text words “exercise,” “exercise therapy,” “hydrotherapy,” “kinesiotherapy,” “physical therapy,” and “rehabilitation.” The search strategy was formulated in PubMed and adapted for use in other databases by an experienced medical librarian (available on request from the authors). To find more studies, the databases mentioned above were also searched for reviews about the effectiveness of exercise therapy in patients with OA. Additionally, the reference lists of all relevant studies and reviews were scanned for potential articles.

Inclusion criteria and procedure.

A study was included in the review if 1) a randomized controlled trial or controlled clinical trial was conducted; 2) the duration between the end of the exercise treatment and one of the followup assessments was at least 6 months; 3) the study was published in Dutch, German, or English; 4) the study was a full-length published article or fully written published report; 5) the study population comprised patients with OA of the hip and/or knee according to accepted American College of Rheumatology (formerly the American Rheumatism Association) criteria (18, 19) or the radiologic criteria of the Kellgren/Lawrence scale (20); 6) ≥1 type of exercise therapy was investigated, with no further restrictions for the type of supervision and group size, excluding perioperative exercise therapy; 7) the study contrast was exercise therapy, allowing additional interventions; and 8) at least 1 of the following outcome measures (i.e., according to the core set of outcome measures as defined by Outcome Measures in Rheumatology Clinical Trials [OMERACT] [21]) was assessed: pain, self-reported physical function, observed physical function, and patient global assessment of effectiveness.

The procedure for inclusion of studies was based on the recommendations described by van Tulder et al (22). The study selection was performed in 2 stages. The first selection, based on titles and abstracts and in consideration of the inclusion criteria, was independently performed by 2 reviewers (MFP and CV). The second step of the inclusion procedure was performed by the same 2 reviewers, who independently applied the selection criteria as stated above using the full reports. Disagreements were resolved by discussion. If agreement was not achieved at any stage, a third reviewer was consulted (JD).

Assessment of methodologic quality.

The methodologic quality of the randomized controlled trials and controlled clinical trials was independently assessed by 2 reviewers (MFP and CV) using the criteria list recommended by the Cochrane Collaboration Back Review Group (22) (see Appendix A, available at the Arthritis Care & Research Web site at http://www.interscience.wiley.com/jpages/0004-3591:1/suppmat/index.html). This list has frequently been applied in rating the methodologic quality of trials in health care and physiotherapy. It contains criteria as proposed by Jadad et al (23) and Verhagen et al (24), and consists of 11 criteria for internal validity: 3 criteria related to selection bias (A, B, and C), 4 criteria for performance bias (D, E, G, and H), 2 criteria for attrition bias (I and K), and 2 criteria for detection bias (F and J). All criteria were scored as “yes,” “no,” or “unclear.” Equal weights were applied. Studies were considered to be of sufficient quality if at least 6 of the 11 validity criteria were met. A consensus method was used to resolve disagreements and a third reviewer (JD) was consulted if disagreement persisted.

Statistical analysis.

A predefined data extraction form with study characteristics, patient characteristics, and baseline, posttreatment, and followup data on outcome was used. For continuous variables, the standardized mean difference (SMD) with corresponding 95% confidence intervals (95% CIs) was calculated if possible (25). These effect estimates were interpreted as described by Cohen (26), i.e., an SMD of 0.2–0.4 was considered a small effect, 0.5–0.7 a moderate effect, and ≥0.8 a large effect of exercise therapy. A contrast between an exercise therapy intervention group and a nontreated control group was preferred. When studies compared the effectiveness of ≥2 exercise intervention groups with each other, the effect estimate was calculated between the 2 groups with the largest contrast in treatment effect. Because the included studies were heterogeneous with regard to study population, study design, outcome measures, and content of exercise therapy, a quantitative analysis (meta-analysis) was considered inappropriate. Therefore, a best evidence synthesis was performed, as proposed by van Tulder et al (22) (Table 1), by taking into account the methodologic quality and consistency of the findings. To determine the robustness of the outcome of the best evidence synthesis, 2 different sensitivity analyses were performed, the first considering studies to be of high quality if ≥4 methodologic quality criteria were met and the second considering studies to be of high quality if ≥8 methodologic quality criteria were met.

Table 1. Best evidence synthesis
  • *

    Consistent findings were defined as ≥75% trials showing results in the same direction.

Strong evidenceConsistent findings in multiple high-quality trials*
Moderate evidenceConsistent findings in multiple low-quality trials and/or 1 high-quality trial
Limited evidenceConsistent findings in outcome measures in at least 1 low-quality trial
ConflictingInconsistent findings among multiple trials
No evidenceNo randomized trials available

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information

Selection of studies.

The search strategy resulted in a list of 3,771 citations. A flow chart of the results of the selection procedure after selection based on title, abstract, and full-text article is presented in Figure 1. The main reasons for exclusion of potentially relevant studies based on full-text articles are also presented in Figure 1. Eleven articles fulfilled all selection criteria and were included in this systematic review. The characteristics of the included studies are presented in Appendix B (available at the Arthritis Care & Research Web site at http://www.interscience.wiley.com/jpages/0004-3591:1/suppmat/index.html). All included studies were randomized controlled trials. Eight of these studies (27–34) investigated the effectiveness of exercise therapy, and 3 investigated the effectiveness of exercise therapy with additional booster sessions posttreatment (35–37). Additionally, 8 of the studies compared exercise therapy with usual care (27, 29–31, 33–36), 2 compared exercise therapy with patient education (32, 37), and 1 compared exercise therapy with subtherapeutic ultrasound therapy (28). The duration of long-term followup assessments varied from 6 to 15 months after treatment ended.

thumbnail image

Figure 1. Flow chart of inclusion procedure. * Multiple reasons per study for excluding were possible. RCT = randomized controlled trial; CCT = controlled clinical trial.

Download figure to PowerPoint

Methodologic quality.

There was initial disagreement between the 2 reviewers on 29 (24%) of the 121 (11 × 11 items) methodologic quality items scored. Nearly all disagreements were due to reading errors or a difference in interpretation of the methodologic criteria. After a consensus meeting, no disagreement persisted.

The methodologic quality of all included studies is presented in Table 2. Five of the studies had high methodologic quality (27, 28, 31, 34, 37) and 6 had low methodologic quality (29, 30, 32, 33, 35, 36). In exercise therapy trials, neither care providers nor patients can be blinded to the treatment. Therefore, none of the included studies met the criteria blinding of care provider (E) and blinding of patients (D).

Table 2. Methodologic quality assessment*
Study (ref.)Fulfilled validity criteriaUnfulfilled validity criteriaIncomplete information for validity assessmentInternal validity scoreMethodologic quality
Selection bias (A, B, and C)Performance bias (D, E, G, and H)Attrition bias (I and K)Detection bias (F and J)
Messier (37), Ettinger (46)A, B, CG, HI, KF, JD, E9High
Rogind (31)A, CG, HI, KF, JB, D, E8High
van Baar (34)A, CG, HI, KF, JD, EB8High
Cochrane (27)A, B, CKF, JD, E, H, IG6High
Deyle (28)A, CG, HF, JB, D, E, I, K6High
Sullivan (33), Kovar (50)A, CHF, JD, E, IB, G, K5Low
Huang (36)A, BHJD, E, IC, F, G, K4Low
Huang (35)A, BHJD, E, I, KC, F, G4Low
Halbert (29)CGJD, EA, B, F, H, I, K3Low
Kuptniratsaikul (30)A, CJD, E, H, IB, F, G, K3Low
Stener-Victorin (32)A, BC, D, E, F, I, J, KG, H2Low

Long-term effectiveness of exercise therapy.

The treatment effect (SMD with 95% CI) of exercise therapy on pain, self-reported physical function, observed physical function, and patient global assessment of effectiveness immediately after the treatment and at long-term followup is presented in Tables 3 and 4. The results are presented separately for studies comparing exercise versus a control group and for studies comparing exercise with additional posttreatment booster sessions versus a control group. From the 11 studies included, 9 studies reported sufficient data to calculate the SMD with their 95% CIs. Five authors were contacted for additional information and/or data.

Table 3. Results on pain and patient global assessment of effectiveness*
Study (ref.)Methodologic qualityNo.PainPatient global assessment of effectiveness§
After treatment SMD (95% CI)Long-term followup SMD (95% CI)After treatment SMD (95% CI)Long-term followup SMD (95% CI)
  • *

    SMD = standardized mean difference; 95% CI = 95% confidence interval; RCT = randomized controlled trial; NE = SMD not estimable; NS = no significant differences between groups reported; NM = not measured.

  • 1 = high quality, 0 = low quality; for more information about the methodologic quality, see Appendix A (available at the Arthritis Care & Research Web site at http://www.interscience.wiley.com/jpages/0004-3591:1/suppmat/index.html).

  • A positive SMD with 95% CI indicates a decrease in pain.

  • §

    A positive SMD indicates an improvement in patient global assessment of effectiveness. If >2 groups were evaluated, the 2 groups with the greatest contrast in intervention were compared.

RCTs comparing exercise versus control      
 Rogind (31)125NE (NS)NE (NS)NMNM
 van Baar (34)12010.45 (0.16, 0.74)0.13 (−0.17, 0.42)0.61 (0.32, 0.90)0.35 (0.06, 0.64)
 Cochrane (27)13120.24 (−0.02, 0.50)0.11 (−0.16, 0.37)NMNM
 Deyle (28)1830.77 (0.31, 1.23)0.41 (−0.10, 0.92)NMNM
 Sullivan (33), Kovar (50)01020.56 (0.00, 1.11)0.40 (−0.16, 0.95)NMNM
 Halbert (29)0690.03 (−0.44, 0.50)0.17 (−0.30, 0.65)NMNM
 Kuptniratsaikul (30)03290.44 (0.24, 0.65)0.12 (−0.09, 0.32)NMNM
 Stener-Victorin (32)045NENE (NS)NMNM
RCTs comparing exercise with additional booster sessions versus control      
 Messier (37), Ettinger (46)11030.79 (0.30, 1.28)0.55 (0.07, 1.03)NMNM
 Huang (36)01200.47 (−0.08, 1.02)1.64 (0.95, 2.32)NMNM
 Huang (35)01321.69 (1.11, 2.26)2.99 (2.21, 3.77)NMNM
Table 4. Results on self-reported and observed physical functioning*
Study (ref.)Methodologic qualityNo.Self-reported physical functionObserved physical function
After treatment SMD (95% CI)Long-term followup SMD (95% CI)After treatment SMD (95% CI)Long-term followup SMD (95% CI)
  • *

    A positive SMD with 95% CI indicates an improvement in self-reported or observed physical function. If >2 groups were evaluated, the SMD of 2 groups with the greatest contrast in treatment effect are reported. S = significant differences between groups reported; see Table 3 for additional definitions.

  • 1 = high quality, 0 = low quality; for more information about the methodologic quality, see Appendix A (available at the Arthritis Care & Research Web site at http://www.interscience.wiley.com/jpages/0004-3591:1/suppmat/index.html).

RCTs comparing exercise versus control      
 Rogind (31)125NE (NS)NE (NS)NE (NS)NE (NS)
 van Baar (34)12010.10 (−0.18, 0.38)0.08 (−0.21, 0.37)NE (S)NE (NS)
 Cochrane (27)13120.23 (−0.03, 0.49)0.11 (−0.16, 0.37)NMNM
 Deyle (28)1830.78 (0.32, 1.24)0.53 (0.02, 1.05)0.67 (0.19, 1.16)0.79 (0.27, 1.32)
 Sullivan (33), Kovar (50)01020.93 (0.36, 1.51)0.04 (−0.51, 0.59)NMNM
 Halbert (29)0690.18 (−0.30, 0.65)0.23 (−0.25, 0.70)NMNM
 Kuptniratsaikul (30)03290.09 (−0.12, 0.29)0.29 (0.09, 0.50)0.75 (0.54, 0.97)0.49 (0.28, 0.70)
 Stener-Victorin (32)045NENE (NS)NMNM
RCTs comparing exercise with additional booster sessions versus control      
 Messier (37), Ettinger (46)1103NMNM0.24 (−0.23, 0.72)0.68 (0.19, 1.16)
 Huang (36)01201.07 (0.55, 1.58)1.52 (0.85, 2.19)1.36 (0.76, 1.97)2.62 (1.81, 3.44)
 Huang (35)01322.22 (1.58, 2.86)2.86 (2.09, 3.62)5.60 (4.46, 6.73)4.69 (3.63, 5.74)

Pain.

Pain was used as an outcome measure in all included studies (Table 3). In these studies, 5 different measures were used to assess pain. In 2 trials the data presentation was insufficient to calculate the SMD (31, 32).

From the 8 studies comparing exercise with a control group, 3 high-quality studies reported small to moderate positive effects on pain posttreatment. However, at long-term followup a decline of these beneficial findings to nonsignificant treatment effects was reported (27, 28, 34). The same results are shown in 2 low-quality studies (30, 33). Two other low-quality studies (29, 32) and 1 high-quality study (31) with small sample sizes reported no significant results, both after treatment and at long-term followup. Furthermore, from the 3 studies comparing exercise with additional booster sessions with a control group, 1 high-quality study (37) and 2 low-quality studies (35, 36) reported a significant treatment effect at long-term followup.

Therefore, strong evidence was found for no long-term effectiveness of exercise therapy on pain in patients with OA of the hip and/or knee. The significant small to moderate posttreatment effects seemed to decline over time and finally disappear at long-term followup. However, there was moderate evidence that additional booster sessions in the period after treatment had a positive influence on maintenance of the posttreatment effects in the long term.

Patient global assessment of effectiveness.

Only 1 high-quality study (34) reported patient global assessment of effectiveness as an outcome measure (Table 3). This study reported a moderate significant posttreatment effect and a small significant treatment effect at long-term followup. This finding provides moderate evidence for the long-term effectiveness of exercise therapy on patient global assessment of effectiveness. However, this moderate posttreatment effect seemed to decline over time toward a small treatment effect.

Self-reported physical function.

Self-reported physical function was reported in 10 studies (Table 4). In these studies, 7 different outcome measures were used to assess self-reported physical function. In 2 of the studies, the data presentation was insufficient to calculate the SMD (31, 32). Three high-quality studies, comparing exercise treatment with a control group, reported nonsignificant effects on self-reported physical function both posttreatment and at long-term followup (27, 31, 34). Two low-quality studies, each with a small sample size, reported similar results (29, 32). Another low-quality study (30) reported no significant posttreatment effect and a small significant effect at long-term followup. One low-quality study (33) reported a large significant posttreatment effect on self-reported physical function. However, in the long term the effect declined and finally disappeared. Finally, 1 high-quality study (28) reported a significant moderate treatment effect posttreatment and at long-term followup. Concerning exercise therapy with additional booster sessions, 2 low-quality studies with a small sample size (35, 36) reported large significant posttreatment effects that increased at long-term followup.

Thus, strong evidence was found for no long-term effectiveness of exercise therapy on self-reported physical function in patients with OA of the hip and/or knee. There was moderate evidence that additional booster sessions in the period after treatment have a positive influence on sustaining the posttreatment effects for a longer period.

Observed physical function.

Observed physical function was reported in 7 studies (Table 4). In these studies, 4 different outcome measures were used to assess observed physical function. In 2 studies the data presentation was insufficient to calculate the SMD (31, 34). Two high-quality studies (28, 34) reported significant posttreatment effects. However, at long-term followup one study (28) reported a significant moderate treatment effect and the other study (34) reported no significant treatment effect. One high-quality study (31) with a small sample size reported no significant effects, both posttreatment and at long-term followup. However, 1 low-quality study (30) reported significant posttreatment and long-term effects on observed physical function. Concerning exercise therapy including additional posttreatment booster sessions, 1 high-quality study (37) and 2 low-quality studies (35, 36) reported small to large significant effects posttreatment and moderate to large significant effects at long-term followup.

Thus, conflicting evidence was found for the long-term effectiveness of exercise therapy in patients with OA of the knee and/or hip on observed physical function. However, moderate evidence was found in favor of additional posttreatment booster sessions having a positive influence on sustaining the posttreatment effects in the long term.

Sensitivity analysis.

When analyzing the results, considering studies that met ≥4 methodologic quality criteria as high-quality studies, the outcome of the best evidence synthesis was, for most outcome measures, the same as the original best evidence synthesis. However, the findings that exercise therapy with additional posttreatment booster sessions have beneficial long-term effects changed from moderate evidence to strong evidence for pain, self-reported physical function, and observed physical function. Furthermore, a sensitivity analysis was performed by considering studies to be high-quality if ≥8 methodologic quality criteria were met. This sensitivity analysis resulted in the same results as presented in the original best evidence synthesis for all outcome measures.

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information

In this systematic review, the long-term effectiveness of exercise therapy in patients with OA of the hip and/or knee was explored. Overall, no long-term effectiveness was found on pain and physical function for exercise therapy in patients with OA of the hip and/or knee. The positive posttreatment effects on pain and physical function declined over time and finally disappeared. Moderate evidence was found for the long-term effectiveness of exercise therapy on patient global assessment of effectiveness, although this outcome measure was only assessed in 1 study. Furthermore, several studies investigated the value of additional booster sessions in the period between posttreatment and long-term followup. The studies with additional booster sessions reported long-term effectiveness on pain and physical function (35–37).

The presented posttreatment effects of exercise therapy in our review are comparable with the reported results in systematic reviews of the short-term effectiveness of exercise therapy, with the exception of self-reported physical function and observed physical function (14, 15). In our review, patients' self-reported physical function showed small and mostly nonsignificant posttreatment results, whereas systematic reviews investigating short-term effectiveness of exercise therapy reported a small significant posttreatment effect on self-reported physical function (14, 15). Concerning observed physical function, moderate posttreatment effects were found in our review, whereas van Baar et al reported small posttreatment effects (15). These differences can be explained by the fact that we focused on long-term effectiveness and therefore did not include all studies investigating short-term effectiveness of exercise therapy.

A small number of studies have investigated potential predictors of long-term outcome in exercise therapy but did not reach consistent findings; only exercise adherence has been shown to be an important predictor (38). However, the literature on adherence is diverse and mostly does not specifically address exercise adherence and strategies to improve adherence among patients with OA (39). Moreover, the related studies that do exist predominantly focused on exercise adherence within the period of treatment. From the general exercise literature, it can be concluded that strategies such as telephone and mail contact (40, 41), self-monitoring using a diary (42, 43), reinforcement (43), and graphic feedback (44) can increase maintenance of exercise adherence in the long term. From the results of our review, it can be concluded that additional posttreatment booster sessions seem to have a positive influence on the maintenance of positive, long-term treatment effects on pain and physical function. In the additional booster sessions, physiotherapists supported and stimulated patients to integrate exercises into their daily living (45). Additional posttreatment booster sessions probably have a positive influence on adherence to exercise and the advice of physiotherapists concerning physical activity behavior. Studies including additional booster sessions reported relatively high exercise adherence rates (50–75%) in the long term (35, 36, 46).

The included studies involved a wide variety of delivery modes, contents, and doses of exercise therapy. In most included studies, the exercise program aimed to improve OA-specific impairments in body structures and/or functions, such as muscle strength, range of motion, and balance. In only 2 studies (33, 46) the exercise treatment also consisted of exercises aiming to improve commonly impaired activities in patients with OA. However, for sustaining the positive posttreatment effects long term, it is hypothetical that exercises should become more functional and task oriented (45). Performance of functional tasks is complex and involves interplay of cognitive, perceptual, and motor functions and is closely linked to the individual's dynamic environment (45, 47). It is expected that exercise training that simulates, as closely as possible, the conditions of daily tasks will enhance exercise adherence posttreatment and therefore positively influence long-term effectiveness of exercise therapy. Because of the heterogeneity of the included studies concerning delivery mode, content, and dose of exercise therapy, it was not possible to provide meaningful subgroup analyses on the long-term effectiveness of exercise therapy.

Some critical remarks can be made on the included studies. First, the most prevalent possible source of bias in the included studies was attrition bias (48): only 4 trials described an acceptable dropout rate (criterion I) and only 4 studies performed their analyses following the intent-to-treat principle (criterion K). Second, the power of 6 studies was rather low (28, 29, 31, 32, 35, 36). To detect a medium effect size of 0.5 (with α = 0.05 and power at 80%), the sample size per group needs to be at least 50 (26). Third, most included studies investigated a standardized exercise program (content, dose, and delivery mode), and therefore these studies did not reflect the reality of exercise therapy administered by physiotherapists in daily practice. Only in 2 studies (29, 34) was the exercise program individualized based on the patients' functional status. Fourth, the large positive effects in both studies by Huang et al (35, 36) that included additional booster sessions are remarkable and should be interpreted with caution, given the low methodologic quality. However, a sensitivity analysis considering only high-quality studies resulted in the same conclusion regarding the positive influence of additional booster sessions on the long-term effectiveness of exercise. Finally, outcome measures were very heterogeneous. All included studies measured one or more outcome dimensions according to the core set of outcome measures as defined by OMERACT, which are pain, physical function, and patient global assessment of effectiveness (21). However, several different outcome measures were used for these dimensions. Recently, Veenhof et al systematically evaluated the psychometric qualities of existing OA questionnaires and recommended outcome measures for evaluating pain and physical function based on both descriptive and psychometric qualities (49). However, international consensus about a core set of outcome measures is needed and would greatly enhance evidence synthesis in future research.

We believe that in addition to evaluating the methodologic quality of studies, it is important for a systematic review to assess the clinical relevance of the included studies to enable clinicians to decide whether the results apply to their population (22). For instance, physiotherapists want to know whether the patients included in a study are comparable with those seen in their own practices, whether the interventions are described well enough to provide the same treatment to their patients, and whether the reported size of the effect is clinically relevant. Recently, van Tulder et al proposed 5 assessment items for scoring clinical relevance of randomized clinical trials (22), but explicitly defined criteria for scoring these items are lacking. In our review, a highly sensitive comprehensive search was conducted following the recommendations of the Cochrane collaboration in order to identify articles of interest, but for practical reasons, only studies published in Dutch, German, or English were included in the final review, which might have led to selection bias.

In conclusion, the positive posttreatment effects of exercise therapy on pain and physical function in patients with OA of the hip and/or knee are not sustained long term. Long-term beneficial effectiveness was only found for patient global assessment of effectiveness. However, additional booster sessions after the treatment period positively influence maintenance of beneficial posttreatment effects on pain and physical function in the long term. Based on this review, we suggest that further research is needed concerning the influence of exercise adherence on the long-term effectiveness of exercise therapy and the effectiveness of different strategies to improve exercise adherence posttreatment. Furthermore, studies are needed that investigate how long beneficial effects of exercise therapy including additional booster sessions are sustained, and how much exercise is required to sustain the beneficial effects of exercise therapy long term.

AUTHOR CONTRIBUTIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information

Mr. Pisters had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study design. Pisters, Veenhof, van Meeteren, Ostelo, Dekker.

Acquisition of data. Pisters, Veenhof.

Analysis and interpretation of data. Pisters, Veenhof, van Meeteren, Ostelo, de Bakker, Schellevis, Dekker.

Manuscript preparation. Pisters, Veenhof, van Meeteren, Ostelo, de Bakker, Schellevis, Dekker.

Statistical analysis. Pisters, Veenhof.

Acknowledgements

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information

We express our gratitude to Noor Breuning for her contribution to the literature search strategy, and to Gail Deyle, Moa-Hsiung Huang, Elisabet Stener-Victorin, and Walter Ettinger for providing additional information and/or data from their studies.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information
  • 1
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Supporting Information

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. Acknowledgements
  9. REFERENCES
  10. Supporting Information
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