Inflammatory low back pain (IBP) is a key clinical feature of axial spondyloarthritis (axSpA) and an important diagnostic clue in patients presenting with chronic back pain. However, IBP is neither disease-specific nor uniformly expressed across inflammatory joint diseases, and its recognition in routine clinical practice remains challenging. Significant symptom overlap with mechanical low back pain, heterogeneity of clinical presentation, limited specificity of imaging findings, and frequent misuse of classification criteria as diagnostic tools contribute to persistent diagnostic uncertainty and delay. Despite advances in imaging and therapeutics, several critical challenges remain unresolved, including the limited specificity of IBP constructs, the risk of MRI overinterpretation, and the unclear nosological status of axial psoriatic arthritis (axial PsA). Moreover, variability in treatment response across disease phenotypes highlights the need for more precise diagnostic and therapeutic frameworks. This narrative review provides a structured and critical synthesis of current evidence on IBP across inflammatory joint diseases. It emphasizes key diagnostic pitfalls, including imaging-related challenges and misapplication of classification criteria, and highlights disease-specific differences between axSpA, axial PsA, and rheumatoid arthritis. In addition, it outlines clinically relevant considerations for diagnostic evaluation and therapeutic decision-making. Future research should focus on the development of integrated diagnostic models, improved imaging interpretation strategies, and disease-specific therapeutic approaches to optimize patient outcomes.