Peripheral Spondyloarthritis: Conceptualization and Diagnosis as a Distinct Rheumatologic Subset of Disease.

Peripheral spondyloarthritis (pSpA) encompasses multiple entities affecting the musculoskeletal system with classic findings of synovitis, enthesitis, and tenosynovitis. It remains poorly defined when compared with the axial spondyloarthritides due to nonspecific symptoms, ill-defined imaging findings, and lack of specific testable biomarkers. Previous research has tried to distinguish between the two disease entities using clinical presentations, scoring systems, and radiographic findings; however, overlap remains. We summarize the current classification of pSpA, imaging findings, and the distinction between these entities and axial spondyloarthritis.