Core stability exercises; Low back pain; Muscle energy technique; Oswestry Disability Index; Physiotherapy; Sacroiliac joint dysfunction; Visual analog scale

The sacroiliac joint (SIJ) transmits load between the spine and the lower limbs and is stabilized by a dense arrangement of ligaments and by the muscular and fascial connections linking the sacrum, pelvis, and trunk [1]. It is a true diarthrodial joint whose ridged articular surfaces and strong posterior ligaments favor stability over mobility, and disturbance of this finely balanced system can become a source of persistent pain [1]. Historically, the SIJ was regarded as a principal cause of low back pain until intervertebral disc pathology dominated clinical thought in the mid-twentieth century, but it is now recognized again as an important contributor to pain in the lower back and pelvic region [2,3]. Contemporary estimates suggest that it accounts for approximately 15 to 30% of cases of chronic, nonradicular low back pain [2].

SIJ dysfunction describes pain arising from the joint, which is typically attributed to either excessive or restricted movement and is often accompanied by muscular imbalance around the pelvis [2,4]. The pain is usually felt at the base of the spine and over the buttock and may be provoked by sitting, rising from a seat, climbing stairs, single-leg loading, or traveling in a vehicle [2]. Because its presentation overlaps with that of lumbar disc herniation, facet joint syndrome, and spinal stenosis, SIJ dysfunction is easily misattributed, and diagnosis relies on a combination of history, palpation, and a battery of provocation tests [2]. Recognized risk factors include leg-length discrepancy, altered gait, prior lumbar fusion [5], and pregnancy, the last of which alters pelvic biomechanics and commonly produces sacroiliac and pubic pain [6,7].

Among the conservative options, the muscle energy technique (MET) is a manual approach in which the patient performs a controlled voluntary muscle contraction against a precisely applied counterforce, after which the tissue is taken to a new length [8]. It is used to restore range of motion, reduce local pain, and normalize muscle function, and its benefits are thought to be mediated through neurological effects, such as reflex muscle relaxation and hypoalgesia, rather than through purely biomechanical change [9]; systematic reviews and trial evidence support its usefulness across a range of musculoskeletal complaints, including neck, shoulder, and low back pain [10,11,12]. Core stability exercise takes a different route to achieve the same goal, training the deep trunk and pelvic muscles that provide segmental control of the spine and pelvis; the rationale is that improved neuromuscular control restores support to the lumbopelvic complex and interrupts the cycle of recurrent mechanical pain [13,14,15].

Low back pain is among the leading causes of disability worldwide [16], and exercise-based rehabilitation is among the most widely recommended conservative approaches [17]; when the SIJ is the source, however, the problem is frequently overlooked, and misdiagnosis can lead to ineffective or unnecessary treatment [2]. For everyday physiotherapy practice, it therefore matters which conservative techniques are effective and whether any one of them is preferable, particularly in settings where access to advanced imaging and interventional options is limited. Despite the popularity of both approaches, evidence on their effectiveness specifically in SIJ dysfunction remains limited, and there is little guidance on how the two compare in routine practice, particularly in private-sector settings in low- and middle-income countries [4,18]. This study was therefore conducted to determine whether MET and core stability exercises reduce pain and disability in adults with SIJ dysfunction and to compare the two techniques directly.

This manuscript is reported in accordance with the TREND statement for nonrandomized evaluations of behavioral and public health interventions [19].

2.1. Study design

A quasiexperimental, nonrandomized, two-group study was conducted, with participants assessed at baseline and again at the end of the third week of intervention.

2.2. Setting and duration

Data were collected from a private-sector hospital in Lahore, Pakistan (Hussain Memorial Hospital), between April and August 2023.

2.3. Participants and eligibility

Adults who presented to the orthopedic, physical therapy, and outpatient departments with a clinical diagnosis of SIJ dysfunction were screened. Eligible participants were men and women aged 20 years or older with pain around the pelvic girdle. Patients were excluded if they had degenerative joint disease, a history of pelvic surgery, or trauma to the pelvic region. Written informed consent was obtained from all participants.

2.4. Sample size

The required sample size was estimated by comparing the primary pain outcome (VAS, 0 to 10) between the two independent treatment groups, using the standard formula for the difference between two independent means [20]: n (per group) = 2σ²(Zα/2 + Zβ)² ÷ d², where Zα/2 = 1.96 (two-tailed α = 0.05), Zβ = 0.84 (80% power), σ = 1.5 is the anticipated common standard deviation of the VAS pain score, and d = 1.0 is the minimum between-group difference in mean VAS considered clinically meaningful for SIJ dysfunction [21]; this threshold was set conservatively, below the minimal important change of approximately 2 points proposed by international consensus for pain in low back pain, so that the calculation would not underestimate the required sample. The assumed standard deviation was based on the VAS pain scores reported for manual therapy and exercise-based interventions in comparable SIJ dysfunction trials [22,23], and it closely matched the baseline VAS variability later observed in this sample. Substituting these values, n = 2 × (1.5)² × (1.96 + 0.84)² ÷ (1.0)² = 2 × 2.25 × 7.84 ÷ 1 = 35.3, rounded up to 36 participants per group. This estimate was cross-checked using G*Power (version 3.1.9.7) for an independent-samples t test with the same parameters [24]. No further allowance for attrition was added, as the short, closely supervised three-week protocol was expected to retain all the enrolled participants. The target enrollment was therefore 72 participants: 36 allocated to the MET group and 36 to the core stability exercise group.

2.5. Sampling and group allocation

Participants were enrolled by purposive (nonprobability) sampling. Seventy-two patients were allocated to two equal groups by a systematic, nonrandom method: each patient received an alphanumeric identifier; those with odd-numbered identifiers were assigned to Group A (MET); and those with even-numbered identifiers were assigned to Group B (core stability exercises). Because this is a systematic allocation rather than true randomization, the baseline comparability of the groups was examined explicitly and is reported below.

2.6. Interventions

Both groups received the same baseline conventional program at each visit: hot pack and transcutaneous electrical nerve stimulation (TENS) for approximately 10 minutes. Each intervention was delivered at low intensity for approximately 30 minutes per session, four sessions per week for three weeks (12 sessions in total). This dosage is consistent with the 12-session protocols commonly reported for manual therapy and stabilization exercise in patients with SIJ dysfunction [18,25].

2.6.1. Group A (MET)

With the patient supine and the therapist on the affected side, postisometric relaxation MET was applied to the quadratus lumborum, erector spinae, iliopsoas, and hamstrings. For each muscle, the patient produced a submaximal isometric contraction (approximately 20 to 30% of maximum) against the therapist’s counterforce for 7 to 10 seconds; after relaxation, the tissue was taken gently to the new restriction barrier and held, with the sequence repeated across the session [8].

2.6.2. Group B (core stability exercises)

Patients performed a graded program of bridging, wall squats, knee-to-chest, and prone contralateral arm-and-leg raise, progressing in hold time and repetitions across the three weeks (for example, bridging progressed from a 5-second hold for 5 repetitions in week one to a 10-second hold for 10 repetitions by week three) [13].

2.7. Outcome measures

Two patient-reported outcomes were recorded at baseline and at the end of week three. Pain was assessed with a visual analog scale (VAS), a 0 to 10 scale anchored at “no pain” and “worst imaginable pain”; four dimensions were recorded (current pain, pain during activity, average pain over the preceding week, and change in pain since the start of treatment) and averaged for analysis. Disability was assessed with the modified Oswestry Disability Index (ODI), a ten-item questionnaire in which each item is scored from 0 to 5; the summed score was expressed as a percentage from 0 (no disability) to 100 (maximum disability), with higher scores indicating greater limitations [26].

2.8. Statistical analysis

The data were analyzed in SPSS version 26. Descriptive statistics were used to summarize the sample, and baseline comparability between groups was tested with independent-samples t tests for continuous variables and the chi-square test for categorical variables. The distribution of change scores was assessed with the Shapiro–Wilk test. Within-group changes from baseline to week three were tested with a paired t test for each group, with the Wilcoxon signed-rank test as a nonparametric confirmation. The two techniques were compared by analysis of covariance (ANCOVA) on posttreatment scores, with the corresponding baseline score entered as a covariate to account for baseline differences [27]; the homogeneity-of-regression-slopes assumption was checked. Statistical significance was set at p ≤ 0.05.

2.9. Ethics

Ethical approval was obtained from the Ethics Review Committee of Hussain College of Health Sciences, Lahore, Pakistan (No. HCHS/2023/ERC/34). The study was conducted in accordance with the Declaration of Helsinki, and confidentiality was maintained throughout.

3.1 Participant characteristics and baseline comparability

Seventy-two patients (36 in each group) were enrolled and analyzed. The mean age was 40.7 years, and 66.7% were women. Because allocation was nonrandom, baseline characteristics were compared between groups (Table 1). The groups were similar in terms of age, sex, and pain duration but differed significantly in years of education, monthly household income, locality, baseline pain severity, and baseline disability, with the MET group being more disabled at baseline (modified ODI 70.7 vs 56.0). These imbalances were addressed in the between-group analysis by adjusting for baseline scores.