Parkinson’s disease (PD) affects over ten million people worldwide; the most prevalent symptoms are motor related and many patients report gait dysfunction as the most debilitating symptom. Although the effects PD has on gait have been well studied, previous literature has failed to consider the impact of comorbidities on gait performance in PD. Osteoarthritis (OA) is a condition characterized by joint deterioration and pain, which when present in the knee can cause gait alterations such as decreased gait velocity, step length, and single support time. Significantly, it has been estimated that upwards of 50% of patients with PD also have OA. To further our understanding of PD and OA interactions, this study will analyze the spatiotemporal parameters of gait to see if differences exist between persons with PD and PD with radiographic evidence of OA. These results may highlight the shortcomings of previous literature focused on PD. Understanding the interactions of PD and OA may also aid physicians by emphasizing the need for multidisciplinary diagnoses and treatment plans. Treating OA, in conjunction with continual treatment of PD, may drastically change treatment outcome, and ultimately improve quality of life.