39 patients with primary knee osteoarthritis were randomized to receive either 9 hyaluronan injections over the course of a year, or to a control group which received no injections. The purpose of the study was to assess the clinical and structure-modifying properties of hyaluronan injection treatment, using arthroscopy to view physical changes at the joint. The primary outcome of interest for the study was arthroscopic analysis, comparing the state of the joint previous to treatment and one year later. Other outcomes included VAS pain scores, functional outcome, quality of life assessment, and radiological assessment of joint spacing. Results found a significant reduction in joint deterioration for patients receiving hyaluronan injections compared to the control group, as well as a significantly improved score for quality of life. No difference between groups was found for VAS pain scores, functional outcome, or joint spacing.