Osteoarthritis (OA) is a common degenerative joint disease. As an important component of the knee joint, the infrapatellar fat pad (IPFP) not only provides mechanical cushioning but also plays an active role in local inflammatory, metabolic, and immune regulation. This review summarizes the anatomical and physiological characteristics of the IPFP and its potential roles in OA pathogenesis, with particular emphasis on inflammation, neural regulation, and mechanical stress. The relationships between IPFP-derived inflammatory cytokines, adipokines, fibrosis, and the development and progression of OA are also discussed. In addition, recent advances in the use of ultrasonography, MRI, and molecular biomarkers for the early diagnosis and prognostic assessment of OA are reviewed. The clinical controversy regarding IPFP preservation versus resection during total knee arthroplasty is further analyzed. Finally, the potential value of the IPFP as a diagnostic biomarker and therapeutic target for OA is discussed, providing a reference for further research and the development of precision diagnosis and treatment strategies for OA.