Osteoarthritis (OA) is a common degenerative condition characterized by pain and loss of function. A pathological biochemical environment with excess inflammatory and catabolic proteins is a major contributor to OA. nSTRIDE® Autologous Protein Solution (APS) is a new therapy under development for the treatment of OA. This therapy is formed from a patient’s blood and contains high concentrations of anti-inflammatory and anabolic proteins. This study assessed the safety and treatment effects of APS. Eleven subjects with early to moderate OA were injected with APS. Subjects were closely monitored for adverse events (AE) following the injection. Treatment outcome measures were obtained before injection. AE and clinical outcomes were assessed at 1 and 2 weeks postinjection and 1, 3, and 6 months postinjection. There were no serious AE or AE that were reported by the investigator as greater than mild in severity. There were no AE that were related to the device. There were minor AE related to the injection procedure, including injection site discomfort (1/11), injection site joint pain (1/11), and procedural nausea (1/11), which resolved quickly and did not require treatment. Mean Western Ontario and McMaster Universities Arthritis Index (WOMAC) composite scores and pain, stiffness, and function subscale scores all showed significant improvement compared to baseline by 2 weeks postinjection. The data presented here suggest that the treatment is safe and show a complication profile that is mild and consistent with similar treatments. A single injection of APS for treatment of early to moderate knee OA led to symptom improvement over the study course. Based on these results, an adequately powered, well-controlled, randomized multicenter study to establish clinical efficacy is warranted.