Abstract: A heat stable, purified, pyrogen-free, heat sterilized fraction of hyaluronic acid suitable for use in formulations for intra-articular treatment of animals which includes minor amounts of sulphated mucopolysaccharides, sulphated ash, chlorides, solvents and less than 0.6% protein, having a molecular weight of less than 750,000 and exhibiting a specific absorbance of a 1% solution at A257nm of less than 3. A formulation for intra-articular treatment of animals including an aqueous solution of the heat stable fraction of hyaluronic acid and preservatives, such as sodium benzoate, methylparaben and propylparaben, having a pH of 6.8-8.0 at 25.degree. C. A method of preparing a formulation for intra-articular treatment of animals involving adding and dissolving methyl parahydroxybenzoate, propyl parahydroxybenzoate and sodium benzoate in hot water, mixing the preservative solution to dissolve the parabens, adding sodium hyaluronate in the solution, adjusting the pH of the resultant solution to 6.8-8.