Does Integration of Graded Motor Imagery Training Augment the Efficacy of a Multimodal Physiotherapy Program for Patients With Frozen Shoulder? A Randomized Controlled Trial

Abstract

Background

Despite the availability of numerous treatment modalities for frozen shoulder, spanning from nonsurgical approaches to surgical interventions, a consensus regarding the most effective treatment remains elusive. Current studies emphasize that pain in frozen shoulder affects central nervous system activity and leads to changes in cortical structures, which are responsible for processing sensory information (like pain) and controlling motor functions (like movement). These cortical changes highlight the importance of including the central nervous system in the management of frozen shoulder. It is therefore recommended that treatment should provide more effective management by focusing not only on the shoulder region but also on the cortical areas thought to be affected.

Questions/purposes

Among patients treated nonsurgically for frozen shoulder, is graded motor imagery added to a multimodal physical therapy program more effective than multimodal physical therapy alone in terms of (1) Shoulder Pain and Disability Index (SPADI) scores, (2) pain with activities and QuickDASH (Q-DASH) scores, and (3) ROM after 8 weeks of treatment?

Methods

In this randomized clinical trial, we considered the following as eligible for inclusion: (1) ROM < 50% compared with the unaffected shoulder, (2) clinically and radiologically confirmed primary frozen shoulder, and (3) 30% loss of joint ROM in at least two planes compared with the unaffected shoulder. Diagnosis of patients was based on patient history, symptoms, clinical examination, and exclusion of other conditions. A total of 38 patients with frozen shoulder were randomly assigned to either the graded motor imagery group (n = 19) or the multimodal physiotherapy group (n = 19). The groups did not differ in age, height, weight, gender, and dominant and affected side. In both groups, there were no losses to follow-up during the study period, and there was no crossover between groups. The multimodal physiotherapy program encompassed a variety of treatments, including stretching exercises, ROM exercises, joint-oriented mobilization techniques, scapular mobilization, strengthening exercises, and the application of cold agents. The graded motor imagery program, as an addition to the multimodal physiotherapy program, included the following steps: (1) left-right discrimination (identifying left and right body parts), (2) motor imagery (mentally visualizing movements), and (3) mirror therapy training (using mirrors to trick the brain into thinking the affected part is moving). Both groups of patients participated in a program of 12 sessions, each lasting approximately 45 minutes, twice a week for 6 weeks. Participants were assessed at baseline, after 6 weeks, and at 8 weeks. The primary outcome was the SPADI score, which ranges from 0 to 100, with higher values denoting greater disability. The minimum clinically important difference (MCID) for SPADI scores is reported to be 13.2 points. Secondary outcomes were shoulder ROM, Numeric Pain Rating Scale activity score (scored from 0 points, indicating “no pain,” to 10 points, indicating “worst pain imaginable”), and Q-DASH score (ranging from 0 to 100 points, with a higher score indicating higher functional disability). Repeated-measures analysis of variance was used to compare means between one or more variables based on repeated observations.

Results

After 8 weeks of treatment, patients treated with graded motor imagery plus multimodal physical therapy experienced greater mean ± SD improvement from baseline in terms of SPADI scores than did the multimodal physical therapy group (65 ± 9 versus 55 ± 12, mean difference 10 points [95% confidence interval 4 to 17 points]; p = 0.01). Graded motor imagery when added to standard therapy did not produce a clinically important difference in pain scores with activity compared with physical therapy alone (7.0 ± 1.3 versus 5.9 ± 1.4, mean difference 1 point [95% CI 0.2 to 2.0 points], which was below our prespecified MCID; p = 0.04). However, improvements in Q-DASH score at 8 weeks were superior in the graded motor imagery group by a clinically important margin (58 ± 6 versus 50 ± 10, mean difference 9 points [95% CI 3 to 14 points], which was below our prespecified MCID; p = 0.01). ROM was generally better in the group that received the program augmented by graded motor imagery, but the differences were generally small.

Conclusion

Adding graded motor imagery to a multimodal physiotherapy program was clinically superior to multimodal physiotherapy alone in improving function in patients with frozen shoulder. However, no clinically superior scores were achieved in ROM or activity-related pain. Additionally, the follow-up period was short, considering the tendency of frozen shoulder to recur. Although adding graded motor imagery provides superiority in many scores and does not require high-budget equipment, the disadvantages such as the difference in some scores being sub-MCID and the need for expertise and experience should not be ignored. Consequently, while graded motor imagery shows promise, further research with longer follow-up periods is recommended to fully understand its benefits and limitations in the treatment of frozen shoulder.

Level of Evidence

Level I, therapeutic study.

Introduction

Frozen shoulder is characterized by pain, progressive loss of ROM, and functional impairment of the glenohumeral joint. The lifetime incidence of frozen shoulder in the general population is between 2% and 5% and up to 20% in patients with diabetes [30, 33]. As the cause of frozen shoulder is not fully understood, there is no consensus on treatment. Currently, the common treatments are pharmacotherapy, physiotherapy, steroids, and intraarticular injections, which are all nonsurgical methods used in the management of frozen shoulder [7, 9]. Physiotherapy management recommended at a moderate level of evidence for frozen shoulder includes multimodal interventions such as cold, electrotherapy, active/passive ROM, capsular stretching, proprioceptive neuromuscular facilitation stretching, and strengthening. Recent studies suggest that central pain mechanisms may play a more important role in frozen shoulder than previously recognized. This paradigm shift suggests that treatment approaches targeting the central nervous system, such as graded motor imagery, may be effective in frozen shoulder [7, 8, 22].

Frozen shoulder shares many features with other entities characterized by chronic pain. Recent studies [19, 34] have demonstrated that chronic pain results in structural changes within the brain. For example, the representation of the painful side of the back is enlarged in patients with chronic low back pain and shifted medially compared with the representation in healthy controls [12]. This cortical reorganization has also been demonstrated for shoulder pain, with abnormal regional homogeneity values in cortical structures compared with the representation in healthy controls [17, 34]. One therapeutic approach designed to reorganize these cortical disruptions is graded motor imagery that aims to gradually facilitate cortical networks without triggering the protective response of pain. Although studies investigating the clinical efficacy of central system-oriented applications are limited, motor imagery–based exercises have been reported to be effective in the rehabilitation of orthopaedic diseases, including stiff elbow, knee osteoarthritis, and postoperative arthroplasty [3, 6, 14].

We therefore asked, among patients treated nonsurgically for frozen shoulder, is graded motor imagery added to a multimodal physical therapy program more effective than multimodal physical therapy alone in terms of (1) Shoulder Pain and Disability Index (SPADI) scores, (2) pain with activities and QuickDASH (Q-DASH) scores, and (3) ROM after 8 weeks of treatment?

Patients and Methods

Trial Design

This parallel-group, 1:1 allocation ratio, double-blind, randomized controlled study was conducted at Harran University Training and Research Hospital from May 2022 to June 2023. We obtained informed written and verbal consent from each participant. The trial was registered in ClinicalTrials.gov (NCT05213351).

Participants

We included patients who were diagnosed with primary frozen shoulder by an orthopaedic surgeon or physiatrist specializing in shoulder disorders, who met the inclusion criteria, and who agreed to participate in the study. The diagnosis of patients was based on patient history, symptoms (pain and ROM limitation), clinical examination (loss of passive and active ROM, no painful arc), and exclusion of other conditions (rotator cuff injuries). In this randomized clinical trial, we considered the following as eligible for inclusion: (1) ROM < 50% compared with the unaffected shoulder, (2) clinically and radiologically confirmed primary frozen shoulder, and (3) 30% loss of joint ROM in at least two planes compared with the unaffected shoulder [23]. In addition, most of the other inclusion and exclusion criteria were also used in the diagnostic phase (Table 1). During the study period, 47 patients diagnosed with frozen shoulder were screened, and 89% (42) of them met the inclusion criteria. Two patients were excluded from the study due to language barriers. One patient was excluded due to treatment with antidepressants, another due to treatment with corticosteroids, and a third due to prior treatment at another clinic. However, three patients were excluded because they expressed a desire to receive treatment from different clinics and declined to participate in the study. One patient also declined to take part in the study. Consequently, a total of 38 eligible volunteers, 19 patients in each group, were included in the study (Supplemental Fig. 1; http://links.lww.com/CORR/B332).

Table 1.

Eligibility criteria for participants

Inclusion criteria	Exclusion criteria
ROM in external rotation, abduction, and flexion < 50% compared with the unaffected shoulder in ≥ 1 of 3 movement directions	Passive joint ROM is within normal limits or external rotation joint ROM is < 30%
Primary frozen shoulder clinically and radiologicallya	For having received treatment for frozen shouldera
Greater than 30% loss of joint ROM in at least 2 planes of motion compared with the unaffected shoulder	Radiographic presence of glenohumeral arthritis
Increasing external rotation and internal rotation limitation in the glenohumeral joint when going from 45° to 90° abduction	Inflammatory joint disease, ipsilateral previous shoulder surgery, rotator cuff disease
Shoulder pain lasting > 3 months that occurs during daily life activities and rest	Psychiatric disorders that may cause noncompliance to medical therapy or physical therapy
Ability to understand the outcome scales	Having a standardized Mini-Mental State Examination score of < 24 points

^aFrozen shoulder is classified as either primary (occurring spontaneously with no known cause) or secondary (associated with trauma, surgery, or other conditions such as subacromial pain).

We used the standardized Mini-Mental State Examination (MMSE) to evaluate mental status. Since a certain cognitive level was required to perform the exercises and the components of graded motor imagery training as desired, individuals with < 24 points on the MMSE were not included in the study [15].

Interventions

Multimodal Physiotherapy Group

A multimodal physiotherapy program was prepared by considering frozen shoulder symptoms and practices recommended in the evidence. The program was called multimodal because a treatment session involves the combination of several different types of treatments such as stretching exercises, ROM exercises, joint-oriented mobilization techniques, scapular mobilization, strengthening exercises, and cold agents. The multimodal physiotherapy program consists of two 45-minute sessions per week for 6 weeks and may vary depending on the patient’s progression (Supplemental Table 1; http://links.lww.com/CORR/B331). A cold pack was applied for 15 minutes at the end of each treatment session. Patients were also asked to perform multimodal exercises at home twice a day for 30 minutes each. Patients were requested to complete a diary to follow the home exercise program.

Graded Motor Imagery Group

Patients in the graded motor imagery group received a program that included graded motor imagery training (left-right discrimination, laterality, motor imagery, and mirror therapy) along with the multimodal physiotherapy program. The duration of graded motor imagery training was 30 minutes, and the multimodal physiotherapy lasted 15 minutes in each session (totaling 45 minutes). To prevent bias, the number of sets and repetitions of multimodal physiotherapy interventions was reduced, ensuring that the treatment durations for both groups were comparable. Additionally, patients were instructed to perform graded motor imagery interventions (20 minutes) and multimodal exercises (10 minutes) at home twice a day.

The Recognise^™ Shoulder application (Neuro Orthopedic Institute) was utilized for lateralization training, marking the initial phase of the program. With access to 160 images within the application, patients were tasked with determining whether each image depicted the right or left shoulder, making their selections accordingly. The subjects were presented with images of shoulders in a variety of positions. The images were not of the patients’ shoulders; rather, they were standardized images of both the left and right shoulders, which ensured consistency in the task. Patients were advised that each image had a transition time of 5 seconds, and if they did not make a selection within this timeframe, the application would automatically progress to the next image. The objective of laterality training is to enhance the precision of the cortical representation of the body [25].

The second stage, motor imagery training, requires the patient to mentally visualize specific shoulder postures without physically moving the shoulder. Moseley et al. [25] characterize this phase of graded motor imagery as preparing the patient for movement. Initially, patients were prompted to mentally picture their shoulders in positions depicted in the provided pictures. Once patients could envision themselves in the desired shoulder posture without experiencing discomfort, they were encouraged to visualize a pain-free movement. To ensure focused training, all sessions were conducted in a room with minimal visual and auditory stimuli, as the brain responds to imagined shoulder movements similarly to actual physical movements [25].

The final stage of graded motor imagery, mirror therapy, entails using a mirror to observe the movement of the unaffected body part, creating the illusion that the painful body part is moving without pain. Patients were instructed to gaze at the mirror image of their unaffected shoulder and replicate the movements they had imagined during the visualization training. Throughout the training, efforts were made to minimize distractions by arranging the environment to reduce sounds, lights, and other stimuli that could divert the patient’s attention. Patients were also asked to remove any accessories worn on their affected arm during the training.

Patients in both groups received treatment sessions twice per week for 6 weeks. After 6 weeks of treatment, all patients were given a 2-week home exercise program.

Home Exercise Program

Patients in both groups received a home exercise program during the 2-week posttreatment follow-up period. The home program included strengthening, joint and capsule stretching, and ROM exercises, all of which were demonstrated to the patients by the physical therapist. An exercise diary was used to track home exercises throughout the treatment process.

Randomization and Blinding

A researcher, unaware of the study objective, generated a computerized list using an online randomization web service (https://www.randomizer.org/) and conducted randomization using sealed opaque envelopes selected by each participant; the researcher assigned patients to either the multimodal physiotherapy group or the multimodal physiotherapy plus graded motor imagery group in a 1:1 ratio. An independent physiotherapist experienced in measuring outcome measures and blinded to group allocation performed assessments at baseline, postintervention (Week 6), and during a 2-week follow-up period (Week 8).

Descriptive Data

Thirty-eight patients who entered the study after randomization and treatment initiation remained in the study throughout the treatment and follow-up periods. At the end of the eighth week, there was no loss to follow-up, no crossover was conducted, and the study was successfully completed with the participation of 19 patients in both groups. No patient reported any complications or side effects during the entire intervention and follow-up period. The mean duration of symptoms was 5.4 months for the multimodal physiotherapy group and 5.6 months for the graded motor imagery group. Prior to intervention, patients in both groups demonstrated substantial pain and disability at both the level of the shoulder and in terms of global function, and there were no important between-group differences (Table 2).

Table 2.

Baseline characteristics of the participants

Variable	MP group (n = 19)	GMI group (n = 19)
Age in years	52 ± 5	54 ± 6
Height in cm	166 ± 6	165 ± 8
Weight in kg	77 ± 8	76 ± 11
BMI in kg/m2	27.8 ± 3	27.5 ± 3
Sex
Male	37 (7)	32 (6)
Female	63 (12)	68 (13)
Dominant side
Right	95 (18)	84 (16)
Left	5 (1)	16 (3)
Affected side
Right	47 (9)	58 (11)
Left	53 (10)	42 (8)
MMSE score	27 ± 1	27 ± 2
Pain intensitya
NPRS activity	7.5 ± 1.6	7.5 ± 1.2
ROM in °
Shoulder flexion	116 ± 12	114 ± 14
Shoulder abduction	96 ± 10	92 ± 13
Shoulder internal rotation	52 ± 10	49 ± 12
Shoulder external rotation	39 ± 6	38 ± 7
Q-DASH scoreb	65 ± 7	68 ± 6
SPADI scorec
Total	71 ± 8	74.3 ± 7
Pain	75 ± 10	77 ± 9
Disability	69 ± 8	72.7 ± 7
SF-12v2 scored
PCS	32 ± 3	30 ± 3
MCS	43 ± 11	47 ± 9

Data presented as mean ± SD or % (n). There were no between-group differences at the 0.05 level in any of the measured parameters. MP = multimodal physiotherapy; GMI = graded motor imagery; MMSE = Mini-Mental State Examination; PCS = physical component summary; MCS = mental component summary.

^aPain intensity was assessed using the 11-point Numeric Pain Rating Scale (NPRS), with scores ranging from 0 (no pain) to 10 (worst pain).

^bUpper extremity function and symptoms were assessed using the QuickDASH (Q-DASH), with scores ranging from 0 (no disability) to 100 (most severe disability).

^cShoulder function was assessed using Shoulder Pain and Disability Index (SPADI), with scores ranging from 0 (no disability) to 100 (most severe disability).

^dHealth-related quality of life was measured with the SF-12 physical and mental scores (ranging from 0 to 100, representing worst to best).

Primary and Secondary Study Outcomes

The primary outcome measure for our study was the SPADI score, which is a 13-item scale that assesses two domains: a 5-item subscale that measures pain and an 8-item subscale that measures disability. The cumulative SPADI score ranges from 0 to 100, with higher values denoting greater disability. In addition, the SPADI is recognized for its reliability and validity in assessing patients with frozen shoulder [5].

Secondary outcome measures included shoulder ROM, pain intensity, Q-DASH scores, and quality of life.

Active ROM of shoulder flexion, abduction, and internal and external rotation were measured with the patient in supine position using a universal goniometer (sensitivity ± 2°) [27]. All assessments were made three times, and the averages were recorded. Activity pain intensity was evaluated using the Numeric Pain Rating Scale (NPRS). The NPRS is an 11-point scale that can be scored from 0 to 10. A score of 0 defines “no pain” and a score of 10 defines “the worst pain imaginable” [28]. Subjective assessment of upper extremity function and symptoms was performed using the Q-DASH, which includes an 11-item questionnaire. The cumulative score of the Q-DASH varies between 0 and 100 points, and similar to the SPADI, a high score is considered to indicate high functional disability [2, 11].

The Short Form 12, version 2 (SF-12v2), which is the shortened version of the SF-36 quality of life scale and consists of 12 questions, was used to assess the health-related quality of life of patients. The SF-12v2 includes two components: physical health and mental health [10, 16].

Ethical Approval

Ethical approval for this study was obtained from the Research Ethics Committee at Istanbul University-Cerrahpasa (IRB study protocol: 28125).

Sample Size

We used G*Power, version 3.1.9.7 (Universitat Kiel), to determine the sample size based on SPADI score as the primary outcome measure. The calculation was based on the effect size of 1.139 for the experimental group, using an alpha of 0.05 at 85% power [18]. The minimum sample size required was 16 patients per group. To ensure that the study maintained adequate statistical power, we recruited 38 patients to be included in the study. This approach accounted for the possibility of patient dropouts.

Statistical Analysis

SPSS software, version 21.0 (IBM), was used in the statistical analysis of the data obtained within the scope of the study. Descriptive statistics of the variables were expressed as mean ± SD, % (frequency) and number of patients, and confidence intervals. Since the number of patients included in the study was > 30, we used the Shapiro-Wilk test to determine whether the data conformed to normal distribution. Since the data followed a normal distribution, parametric tests were used in the analysis.

The independent-samples t-test and chi-square test were used to compare baseline variables of two independent groups. The independent-samples t-test was used to analyze the difference between groups after treatment and follow-up and the paired-samples t-test was used to analyze within-group change. We used the repeated-measures analysis of variance to compare means between one or more variables based on repeated observations. Difference in change within and between groups from baseline to Week 8 are reported with 95% confidence intervals, and p ≤ 0.05 was accepted as a significant value.

The outcomes were compared with the minimum clinically important differences (MCIDs) that have been identified and documented by prior studies. Previous findings were that the MCIDs for the SPADI, NPRS, Q-DASH, and SF-12 physical component summary were 13.2 points [29], 1.1 points [24], 8 points [24], and 6.5 [32] points, respectively.

Results

SPADI Scores

After 8 weeks of treatment, patients treated with graded motor imagery plus multimodal physical therapy experienced greater mean improvement from baseline in terms of SPADI scores than did the multimodal physical therapy group (65 ± 9 versus 55 ± 12, mean difference 10 points [95% CI 4 to 17 points]; p = 0.01) (Fig. 1A).

Fig. 1.

The changes in outcome measurements at baseline, 6 weeks, and 8 weeks are shown here for (A) SPADI, (B) Q-DASH, and (C) NPRS. MP = multimodal physiotherapy; GMI = graded motor imagery. A color image accompanies the online version of this article.

Pain With Activity and Q-DASH Scores

The addition of graded motor imagery to standard therapy did not result in a clinically meaningful difference in pain scores when engaging in activities, as compared with physical therapy alone (7.0 ± 1.3 versus 5.9 ± 1.4, mean difference 1 point [95% CI 0.2 to 2.0 points], which was below the prespecified MCID; p = 0.04) (Fig. 1C). However, improvements in the Q-DASH score at 8 weeks were superior in the graded motor imagery group by a clinically important margin (58 ± 6 versus 50 ± 10, mean difference 9 points [95% CI 3 to 14 points], which was below our prespecified MCID; p = 0.01) (Fig. 1B).

ROM and Other Secondary Endpoints

ROM was generally better in the group that received the graded motor imagery program, but the differences were generally small (Table 3). Although a specific MCID value for shoulder ROM has not been reported, the addition of graded motor imagery to the multimodal physiotherapy program demonstrated superiority at Week 8, with a notable difference (mean difference 12.3° [95% CI 2.4 to 22.2]; p = 0.01) (Table 3).

Table 3.

Mean changes from baseline to 8 weeks in SPADI scores, Q-DASH scores, and ROM

Parameter	GMI group (n = 19)	MP group (n = 19)	Mean difference (95% CI)	p value
SPADI total score	65 ± 7	54 ± 8	10 (3.7-17.2)	0.01
SPADI pain score	69 ± 11	57 ± 10	12 (4.3-18.7)	0.01
SPADI disability score	63 ± 9	53 ± 13	10 (2.7-16.9)	0.03
Q-DASH score	58 ± 6	50 ± 10	9 (3.4-14.1)	0.01
Flexion in °	46 ± 12	35 ± 16	11 (2.0-20.7)	0.61
Abduction in °	57 ± 13	45 ± 17	12 (2.4-22.2)	0.01
Internal rotation in °	22 ± 8	18 ± 5	5 (0.2-9.1)	0.13
External rotation in °	28 ± 6	22 ± 7	6 (1.3-10.2)	0.04

Data are presented as mean ± SD. We set the significance level at < 0.05.

There were clinically important differences in improvements in the SF-12 physical function score at 8 weeks with the addition of graded motor imagery to the multimodal physiotherapy program (22 ± 4 versus 17 ± 7, mean difference 5 [95% CI 1 to 9]; p = 0.04). There were no differences in any of the other comparisons among the groups (Table 4).

Table 4.

Mean changes from baseline to 8 weeks in secondary outcome scores

Parameter	GMI group (n = 19)	MP group (n = 19)	Mean difference (95% CI)	p value
NPRS activity score	7 ± 1	6 ± 1	1 (0.2 to 1.9)	0.04
Quality of life
SF-12 PCS	22 ± 4	17 ± 7	5 (1 to 9)	0.04
SF-12 MCS	2 ± 7	5 ± 7	3 (-1 to 8)	0.08

Data are presented as mean ± SD.

Discussion

The current literature emphasizes that changes in cerebral cortical regions affecting pain and ROM are observed in patients with frozen shoulder [19, 34]. It is therefore crucial that treatment strategies address not only peripheral structures but also the central system. Although graded motor imagery, one of the treatment methods targeting cortical structures, has been demonstrated to be efficacious in numerous orthopaedic disorders, its efficacy in treating frozen shoulder patients has not been sufficiently investigated [3, 6, 14]. Therefore, we sought to determine whether the incorporation of graded motor imagery into a multimodal physiotherapy program would prove more efficacious in enhancing function, alleviating pain, and improving ROM in patients diagnosed with frozen shoulder. The present study demonstrated that the addition of graded motor imagery to a multimodal physical therapy program resulted in differences in functional outcomes when compared with the multimodal physical therapy program alone. Furthermore, the results for pain intensity scores and flexion and abduction ROM demonstrated superior outcomes in the group that received graded motor imagery, although the differences were clinically insignificant.

Limitations

Some limitations of this study should be noted. The primary limitation lies in the fact that this clinical trial compared two competing interventions without the use of a true control group, which limited our ability to discern whether the observed effects were because of a placebo effect or the natural history of the disease. Second, due to our study’s small sample size, there exist small differences that we could not detect. Such occurrences can significantly skew outcomes, particularly in instances where there are notable improvements or deteriorations in a few patients. Third, while assessors were blinded to the interventions, the patients were not, potentially leading to a “halo effect.” This phenomenon may constitute a significant constraint on objectivity and impartiality. Fourth, the study is limited in terms of its external validity due to the uncommon use of graded motor imagery. The efficacy of this approach may be diminished if not administered by an experienced and knowledgeable clinician.

A further limitation of the study is the lack of long-term follow-up. Although the follow-up period is insufficient for evaluating the long-term effects of graded motor imagery, this does not invalidate our findings. The focus of our study was on short-term outcomes measured at 8 weeks to understand the immediate effect of graded motor imagery. In this respect, while acknowledging the necessity for long-term studies, our findings provide valuable insights into the short-term efficacy and feasibility of graded motor imagery as an intervention. Ultimately, due to the limited sample size and imbalance in gender representation, a gender analysis was not conducted. Consequently, while we cannot assume equal effectiveness of the interventions for men and women separately, the similarity in gender distribution among the groups should be noted.

SPADI Scores

The addition of graded motor imagery to a multimodal physiotherapy program resulted in clinically important improvements in SPADI scores compared to the multimodal physiotherapy program alone. These findings underscore the potential impact of adding graded motor imagery to multimodal physiotherapy programs on improving short-term functional outcomes in patients with frozen shoulder. Specifically, these improvements are crucial for enhancing daily functioning and reducing disability in this population. To our knowledge, only two studies [13, 20] have reported the effect of graded motor imagery on frozen shoulder. Both studies indicated clinically important improvements in SPADI scores following graded motor imagery intervention, which aligns closely with our findings. However, one of these studies [20] included only 10 patients and lacked a control group, while the other [13] reported only the comparison between before and after treatment (Week 3).

Pain With Activity and Q-DASH Scores

Our findings indicate that incorporating graded motor imagery into a multimodal physiotherapy program yields better results in pain reduction and improvement in Q-DASH scores. However, while adding graded motor imagery results in clinically important improvements in the Q-DASH score, it does not lead to similar advantages in pain intensity reduction compared to a multimodal physiotherapy program alone. These results are consistent with studies demonstrating the efficacy of graded motor imagery in reducing pain intensity [1, 4, 31]. It is hypothesized that the greater reduction in pain experienced by the subjects in the graded motor imagery training group is a result of the approach targeting central structures. Nevertheless, it is estimated that no clinical differences were observed because multimodal physiotherapy was also found to be effective in reducing pain (mean NPRS score of 1.43 points at Week 8).

ROM and Other Secondary Endpoints

The incorporation of graded motor imagery into a conventional physical therapy program frequently resulted in enhanced ROM, but the effect sizes were often small and of questionable clinical importance (Table 3), and likewise, quality of life scores did not improve very much in the graded motor imagery group (Table 4). This is not necessarily surprising because the minimal additional benefits of graded motor imagery might be due to the already significant improvements achieved through the standard multimodal physiotherapy program alone. This could explain why graded motor imagery demonstrated small effect sizes. Supporting our findings, a recent meta-analysis reported that physiotherapy interventions were effective in the treatment of frozen shoulder and that exercises and mobilizations should be included in the treatment program of patients [7]. Furthermore, the current evidence indicates that the pain that causes movement limitation is a top-down and bottom-up phenomenon [26]. It is therefore proposed that the incorporation of a top-down approach, such as graded motor imagery, into a multimodal physiotherapy program will result in further enhancement of ROM and a further reduction in pain intensity. However, it is acknowledged that the clinical impact of this approach may be limited.

The presence of pain, restricted ROM, and functional disability in frozen shoulder syndrome has a detrimental impact on the quality of life of affected individuals. Our findings indicated that adding graded motor imagery to a multimodal physiotherapy program was clinically superior to a multimodal physiotherapy program alone in terms of SF-12 physical component summary score. In the study investigating the reliability, sensitivity, and responsiveness of the SF-12, the physical health component was reported to have an excellent responsiveness score of 1.51, whereas the mental health component was shown to have no responsiveness in patients with rotator cuff tears [21]. We believe that there is a lack of sensitivity because the questions in the SF-12 focus on lower extremity problems rather than upper extremity problems, and for this reason, changes in the mental health component score are not important.

Conclusion

This study demonstrated that adding graded motor imagery to a multimodal physiotherapy program may reduce pain and improve functional outcomes in patients with frozen shoulder. However, no clinically superior scores were achieved in ROM or activity-related pain. Additionally, the follow-up period was short, considering the tendency of frozen shoulder to recur. Nevertheless, advantages such as superiority in many scores, despite being sub-MCID, and the fact that graded motor imagery training does not require high-budget equipment, as well as disadvantages such as the need for expertise and experience, should not be ignored. Consequently, while graded motor imagery shows promise, further research with longer follow-up periods is recommended to fully understand its benefits and limitations in the treatment of frozen shoulder.

Supplementary Material

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