Fluid compositions and methods for lubrication of mammalian joints are disclosed, including both natural and artificial fluids. Synovial fluid acts to lubricate the bearing surfaces of bones and bone-like structures which are held in frictional contact within biological joints. Such fluids may be used to treat arthritic, injured, and diseased joints. Synovial fluid containing a dextran-based hydrogel with lipids provides enhanced rheological and tribological properties of such a fluid. Phospholipids are particularly useful in dextran-based compositions for synovial fluid. One phospholipid that can be used advantageously in synovial fluid is dipalmitoyl phosphatidylcholine (DPPC).