20 patients undergoing arthroscopic treatment with lavage for knee osteoarthritis were randomized to either receive 3 hyaluronic acid (HA) injections starting 2 weeks after arthroscopy or to receive no hyaluronic acid treatment. The purpose of the study was to determine if HA injection provided additional benefits to pain reduction when used in conjunction with arthroscopic treatment. Outcomes included VAS scores for pain at night, pain during movement with a load of 10% body weight, and pain during most the most painful knee movements, as well as the number of pain medication tablets taken daily. Results suggested a significantly greater improvement in all outcomes from week 2 to 24 for patients undergoing HA injection treatment, compared to those undergoing arthroscopy alone.