The study, a cross-sectional study titled -Correlation between Latissimus Dorsi Muscle Length and Contralateral Gluteus Maximus Muscle Strength in Patients with Chronic Mechanical Low Back Pain. The study aims to investigate the relationship between latissimus dorsi (LD) tightness and contralateral gluteus maximus (GM) weakness in patients with chronic mechanical low back pain (CMLBP). Low back pain is one of the most common musculoskeletal problems globally, often linked to muscle imbalance, fascial dysfunction, and altered biomechanics. The thoracolumbar fascia (TLF) connects the LD and contralateral GM as part of the posterior oblique sling system, which plays a crucial role in spinal and pelvic stability. The posterior sling, which connects the latissimus dorsi muscle and the gluteus maximus muscle through the thoracolumbar fascia. Dysfunction in this system may lead to compensatory movement patterns, postural abnormalities, and persistent pain. While past studies have independently examined LD tightness and GM weakness in CMLBP, their direct correlation has not been established. This study plans to assess LD muscle length and GM strength bilaterally using standardized tests, alongside functional disability through the Modified Oswestry Low Back Pain Disability Questionnaire. Data from patients aged 24–55 years who have pain more than 3 according to the NPRS score and more than 3 months of lower back pain. The latissimus dorsi muscle tightness will be checked with the muscle length test, and the gluteus maximus muscle strength will be checked with a manual muscle test bilaterally. The results will be analyzed using appropriate statistical tests to determine whether a significant correlation exists, providing evidence for improved rehabilitation strategies that focus on both LD mobility and GM strengthening.