This study investigates the association between osteoarthritis (OA) and hypertension using observational data from the National Health and Nutrition Examination Survey (NHANES) and Mendelian randomization (MR) analysis. The NHANES data included 24,871 participants, and weighted logistic regression was used to explore the connection between OA and hypertension. After adjusting for multiple confounding factors, no significant relationship was found between OA and hypertension (OR 1.30, 95% CI 0.97–1.73, P = 0.089). However, among males, OA was associated with a higher risk of hypertension (OR 2.25, 95% CI 1.17–4.32, P = 0.019). MR analysis, which used genetic instruments, did not uncover any causal relationship between OA and hypertension, with no significant results across different OA phenotypes and genders. The study concludes that while OA patients had a higher risk of hypertension among males in the observational study, MR analysis did not find a causal link between the two conditions.This study investigates the association between osteoarthritis (OA) and hypertension using observational data from the National Health and Nutrition Examination Survey (NHANES) and Mendelian randomization (MR) analysis. The NHANES data included 24,871 participants, and weighted logistic regression was used to explore the connection between OA and hypertension. After adjusting for multiple confounding factors, no significant relationship was found between OA and hypertension (OR 1.30, 95% CI 0.97–1.73, P = 0.089). However, among males, OA was associated with a higher risk of hypertension (OR 2.25, 95% CI 1.17–4.32, P = 0.019). MR analysis, which used genetic instruments, did not uncover any causal relationship between OA and hypertension, with no significant results across different OA phenotypes and genders. The study concludes that while OA patients had a higher risk of hypertension among males in the observational study, MR analysis did not find a causal link between the two conditions.