Introduction: The progressive and chronic characteristics of knee osteoarthritis imply the presence of symptoms, such as pain, stiffness, and functional capacity difficulty to varying degrees. However, associated psychosocial phenomena, such as kinesiophobia, may also arise, impeding the patient’s recovery. The aim of this study is to determine the association among pain, stiffness, functional capacity, and kinesiophobia in patients with knee osteoarthritis at Hospital Nacional Hipolito Unanue, Peru, in the first two months of 2020. Materials and methods: An observational, correlational, cross-sectional study was conducted on 88 patients with knee osteoarthritis who were selected by census sampling. The Western Ontario and McMaster Universities Osteoarthritis Index questionnaire and the Tampa Scale for Kinesiophobia were used to measure pain, stiffness, functional capacity and kinesiophobia, respectively. Pearson’s chi-square test (p < 0.01) was used for bivariate analysis. Results: The results showed a mean age of 66.38 years and a higher frequency in the female sex (68.2 %), current occupation without physical workload (56.8%), secondary level education (40.9%), time of illness of 1–5 years (51.1 %), bilateral lower limb involvement (68.18 %), moderate pain (51.1 %), moderate stiffness (51.1 %), functional capacity difficulties (61.4 %), and a high level of kinesiophobia (60.2 %). A relationship was found between the variables of pain, stiffness, and functional capacity associated with kinesiophobia (0.000). Conclusions: Pain, stiffness, and functional capacity are associated with kinesiophobia in patients with knee osteoarthritis. The degree of symptomatology increases with the increasing level of kinesiophobia.