Knee osteoarthritis (KOA) and osteoporosis (OP) are closely related, age-related, degenerative orthopedic conditions. Elderly patients with OP frequently develop concurrent KOA, with high co-occurrence rates. Studies indicate that OP significantly increases KOA risk and that these conditions mutually exacerbate each other. Anti-OP therapies show significant efficacy in KOA management, substantially delaying disease progression. Mesenchymal stem cell-derived exosomes (MSC-Exos) have significant therapeutic potential for both KOA and OP. These exosomes enhance chondrocyte proliferation, modulate cartilage matrix synthesis and degradation, and suppress synovial inflammation, suggesting a novel therapeutic approach for KOA. However, their OP mechanisms remain unclear but may involve disrupted bone metabolic signaling, amplified inflammation, and dysregulated intercellular communication in the bone microenvironment. The present review summarizes MSC-Exos research advances in KOA and OP, providing a foundation for future studies and clinical applications.