The effect of addition of liposomes of dipalmitoyl phosphatidylcholine (DPPC) and γ-globulin on the natural joint lubrication was evaluated through pendulum friction tests. The frictional characteristics of pig shoulder joints were confirmed to depend on the viscosity of lubricants only in the physiologically low-load condition and immediately after the loading. A detergent (polyoxyethylene p-t-octylphenyl ether) was successfully used to remove adsorbed films from the articular surfaces. The friction coefficient of natural joints was significantly increased in mixed lubrication mode with a saline solution of sodium hyaluronate (0.2 g/dl) by surface treatment with the detergent. The addition of liposomes of Lα-DPPC or γ-globulin significantly improved the boundary lubricating ability of the articular surfaces treated with the detergent, depending on the quantity of the additives. It appears that the liposomes of Lα-DPPC and γ-globulin can form protective films on the articular surfaces in severe frictional condition.