The invention relates to methods of lubricating biological tissue, such as joints, bone, ocular tissue, nasal tissue, tendons, tendon capsule, and vaginal tissue, by contacting the biological tissue with an effective amount of a block copolymer lubricating composition which functions at least or better than lubricin. In particular embodiments, the method is used to treat osteoarthritis. In specific embodiments, the block copolymer has an ammonium- containing polymer block and a non-ionic hydrophilic polymer block, or the copolymer has a carboxylic acid-containing polymer block and a non-acid non-ionic hydrophilic polymer block.