Background: Mechanical low back pain (MLBP) is a leading cause of disability worldwide, with well-established risk factors such as obesity, occupational ergonomics, and core muscle strength. However, the role of pes planus (flat foot) as a contributing factor remains underrecognized. This study aims to investigate the association between flat foot and MLBP using Clarke’s angle as an objective measure of foot posture. Methods: A case-control study was conducted in South Timor Tengah Regency, East Nusa Tenggara, Indonesia, from December 2024 to February 2025. Fifty patients diagnosed with MLBP and 50 healthy controls were enrolled. Foot type assessment was performed using Clarke’s angle, with a cutoff of ≤30° indicating flat foot. Pain severity in the LBP group was recorded using the Numerical Rating Scale (NRS). Statistical analysis was conducted using chi-square and independent t-tests, with significance set at p < 0.05. Results: Flat foot was significantly more prevalent in the LBP group (58%) than in the control group (18%) (p = 0.000; OR: 6.29, 95% CI: 2.52-15.69), indicating that individuals with flat feet are over six times more likely to experience MLBP. No significant differences were observed between the groups regarding BMI, age, or gender. Conclusion: These findings suggest that flat foot is an independent risk factor for MLBP, likely due to altered spinal biomechanics and compensatory postural changes. Clinicians should consider foot posture assessments in MLBP patients and explore targeted interventions, such as orthotic support, to mitigate symptoms.

Background: The sacroiliac joint (SIJ) plays a crucial role in transmitting axial loads and maintaining pelvic stability. Sacroiliac joint arthropathy (SIJA) accounts for 10%–30% of low back pain cases but remains underrecognized due to overlapping pain referral patterns and nonspecific imaging findings. Diagnosis relies primarily on characteristic pain distribution and provocative maneuvers, with image-guided intra-articular block serving as the diagnostic gold standard. This study aimed to characterize the clinical profile of block-confirmed SIJA, emphasizing referral pain distribution, triggering position, and provocative test responses. Methods: A cross-sectional study was conducted on 98 patients with diagnostic block–confirmed SIJA at Siloam Hospital Lippo Village, Indonesia. Demographic data, referral pain sites, sitting duration, and results of FABER, compression, and distraction tests were analyzed descriptively. Results: The mean age was 52.07 ± 14.17 years, with 72.4% females. Referral pain most frequently involved the lower back (28.6%) and thigh (28.6%), with occasional extension to the groin (8.2%) or calf (4.1%). Over half of patients (55.1%) reported sitting more than six hours daily. Pain was predominantly triggered during sit-to-stand transitions (85.7%) and while sitting (74.5%). SIJ tenderness (98.0%) and FABER positivity (75.5%) were most consistent. Conclusion: The dominant referral pain in SIJA involves the lower back and posterior thigh. Sit-to-stand transition is the most frequent triggering position, while FABER testing demonstrates the highest diagnostic yield among provocative maneuvers. These consistent patterns may serve as practical clinical indicators to improve diagnostic accuracy in suspected SIJ-related pain.