BackgroundThe significance of studying Kinesiophobia, Limits of Stability (LOS), and functional balance in geriatric patients with CLBP and osteoporosis lies in their profound impact on rehabilitation outcomes and fall risk, ultimately affecting patients’ quality of life. This study aimed to examine LOS and functional balance in the geriatric population concurrently experiencing Chronic Low Back Pain (CLBP) and osteoporosis, in comparison to age-matched healthy controls; to assess the correlations between Kinesiophobia, LOS, and functional balance assessments; and to evaluate the mediating influence of Kinesiophobia on the association between LOS and functional balance tests.MethodsThis cross-sectional study included a total of 86 participants in each group. Kinesiophobia was assessed using the Tampa Scale of Kinesiophobia (TSK). LOS variables were evaluated with a computerized Iso-free platform in eight different directions. Functional balance was measured using the Timed Up and Go (TUG) test and the Berg Balance Scale (BBS).ResultsPatients with CLBP and osteoporosis showed significantly lower LOS percentages (45.78 ± 6.92) and impaired Functional Balance, reflected in a TUG Score (10.45 ± 2.23), compared to asymptomatic controls (LOS: 76.95 ± 8.21; TUG: 8.73 ± 1.90). Kinesiophobia showed a significant moderate negative correlation with LOS, indicated by r = −0.362 (p < 0.01). Additionally, Kinesiophobia was found to correlate with functional balance tests. Specifically, there was a moderate positive correlation with the TUG Score (r = 0.322, p < 0.01), indicating that higher Kinesiophobia is associated with slower TUG performance. Conversely, a stronger moderate negative correlation was observed with the Berg Balance Scale (BBS) Score (r = −0.436, p < 0.001), suggesting that increased Kinesiophobia is associated with lower BBS scores, indicating poorer balance performance. Mediation analysis revealed that Kinesiophobia significantly influences LOS and Functional Balance. For LOS and the TUG score, Kinesiophobia showed a direct effect (B = 0.24), an indirect effect (B = 0.09), and a total effect (B = 0.13). Similarly, for LOS and the BBS score, the direct effect of Kinesiophobia was B = 0.38, with an indirect effect of B = 0.10 and a total effect of B = 0.20.ConclusionThis study underscores the substantial impact of Kinesiophobia on both stability and functional balance in individuals coping with CLBP and osteoporosis. The findings emphasize the clinical relevance of addressing Kinesiophobia as a potential target for interventions aimed at improving LOS and functional balance in this specific patient population.