Degenerative joint disease is a dynamic pathological process characterised by a destabilisation of the degradation and synthesis processes of articular cartilage and subchondral bone layer. Studies suggest that individuals with gonarthrosis experience deficits in proprioception, in addition to changes within their joints, which directly affects their ability to maintain posture and increases their risk of falling. Objectives: The aim of this study was to assess the functional status of patients with gonarthrosis through a posturographic examination conducted on a stabilometric platform (force plate) and a functional clinical examination. Methods: Participants were divided into two groups—a control group (n = 125) and a study group (n = 125). During the qualification process, subjective and objective examinations were conducted, including a functional assessment by means of such tests as the “Up and Go” Test, Functional Reach Test, Five Time Sit to Stand Test, and the Step Test. Subsequently, an assessment was conducted on the force plate by means of a posturographic test—the Romberg test performed with open and closed eyes in a standing position—and balance was evaluated using the Berg Balance Scale. The obtained data were analysed with the use of the IBM SPSS Statistics software version 27.0, by means of the Mann–Whitney test, and correlations were determined by means of Spearman’s test. A significance level of p = 0.05 was adopted. Results: Statistically significant differences were observed among the assessed groups as a result of both functional and posturographic examinations, along with positive correlations for disease duration, age, and BMI index. Conclusions: Patients with gonarthrosis exhibited disturbances in balance, functionality, and posture compared to healthy individuals in the control group.