Osteoarthritis (OA) is a degenerative joint disease characterized by articular cartilage degradation including extracellular matrix (ECM) degradation and cell loss. It is known that phosphoinositide-specific phospholipase gamma 1 (PLC gamma 1) can trigger several signaling pathways to regulate cell metabolism. However, whether this kinase is expressive and active in human OA chondrocytes and its role in the pathological progression of OA have not been investigated. The current study was designed to investigate the PLC gamma 1 expression in human OA cartilage, and whether PLC gamma 1 was involved in the ECM synthesis had been further explored using cultured human OA chondrocytes. Our results indicated that PLC gamma 1 was highly expressed in human OA chondrocytes. In our further study using the cultured human OA chondrocytes, the results demonstrated that the disruption of PLC gamma 1 by its inhibitor, U73122, and siRNA contributed to the ECM synthesis of human OA chondrocytes through regulating the expression of ECM-related signaling molecules, including MMP-13, Col II, TIMP1, Sox-9, and AGG. Furthermore, PLC gamma 1/IP3/Ca(2+)/CaMK II signaling axis regulated the ECM synthesis of human chondrocytes through triggering mTOR/P70S6K/S6 pathway. In summary, our results suggested that PLC-gamma 1 activities played an important role in the ECM synthesis of human OA chondrocytes, and may serve as a therapeutic target for treating OA.