The Y-balance test is a modified Star Excusrion Balance Test (SEBT). Plisky proved that the Y-balance test is a reliable and valid test for assessing dynamic stability. The results of previous studies have shown the reliability and validity of the SEBT after a 6-week exercise program in patients with osteoarthritis of the knee. The study was conducted on a group of 19 subjects, patients with osteoarthritis of the knee. A Y-balance test modeled on the SEBT test was used in the study. Physical therapies and the research itself were conducted at two locations. Respondents were divided into two groups. The experimental group of subjects had a 10-day physical therapy that included standard therapeutic exercises and proprioceptive exercises at the Clinical Institute for Rehabilitation and Orthopedic Aids of the University Hospital Centre Zagreb, while the control group had a standard exercise program for knee osteoarthritis at Thalassotherapy Opatija. Measurement by Y-balance test was performed 3 times. The first and second measurements were used to calculate the test reliability by the Test-retest method, while the second and third measurements were used to assess the effect of therapeutic proprioception exercises on dynamic stability in people with osteoarthritis of the knee. This study found that the Y-balance test modeled on SEBT can be reliably used as a good indicator of dynamic stability in a composite measurement result. Although there is no significant difference between the control and experimental groups of subjects, it can be seen that for a certain percentage there is a greater shift in dynamic stability in favor of the experimental group that had the addition of proprioceptive exercises. If the study were conducted over a longer duration of therapies, there might be a statistically larger significant difference in favor of the experimental group of subjects.