48 career late-career professional athletes with degenerative knee cartilage lesions were randomized to receive treatment with either intra-articular injections of either platelet-rich plasma (PRP) or high-molecular-weight hyaluronic acid (HA). The study was conducted in order to determine if there were any significant differences between injections in improving pain and function symptoms. Findings displayed that while the PRP group showed significantly greater improvement in outcomes than the HA group at 3 and 6 months, results at 12 months were not significantly different between groups.