Abstract Background Background. The aim of study was to evaluate the enthesis in patients with inflammatory bowel diseases (IBD) and to assess the involvement of enthesis in different IBD behavior. Methods Methods. 95 IBD pts were prospectively enrolled into the study: 55 pts with ulcerative colitis (UC) and 40 - with Crohn’s disease (CD). The average duration of the disease was 48 (12; 102) months in UC, and 42 (18; 87) months in CD. The severity of UC exacerbation was assessed by the Mayo index, in CD – by Harvey-Bradshaw index. In UC, moderate and severe exacerbation was revealed in 40 pts (73%), in CD - in 17 (43%). Among 95 pts with IBD, extraintestinal manifestations occurred in 67 pts (71%), of which 34 (62%) pts with UC and 33 (82%) pts with CD. 70 enthesis were evaluated clinically and by US in each pt. The clinical examination included tenderness of enthesis, US examination with power Doppler detected inflammatory (hypoechogenicity of enthesis, thickening of enthesis, presence of vascularization) and structural (erosion, enthesophyte) changes in enthesis. Fisher’s exact test, Spearman’s coefficient and binary logistic regression to determine the odds ratio (OR) were used to calculate differences. Results Results. The duration of IBD course directly correlated with the number of tender entheses (SR = 0.24; p = 0.017), as well as the number of enthesophytes (SR = 0.20; p = 0.044). The severity of IBD exacerbation and enthesis involvement didn’t have statistically significant correlation. However, the inflammatory lesions of entheses (the number of erosions with vascularization) correlated with CRP level (SR = 0.25; p = 0.01). We also identified a relationship between the presence of extraintestinal manifestations and the enthesis involvement: for example, the presence of at least one extraintestinal manifestation increased the likelihood of detecting erosions by 4.77 times (95% CI 1.6–13.9, p = 0.003). The presence of joint pain increased the likelihood of detecting erosions of entheses by 3.37 times (95% CI 1.18–9.65, p = 0.02). Clinical signs of musculoskeletal system involvement (tenderness of enthesises on palpation) significantly increased the frequency of enthesitis, including vascularized enthesitis (p = 0.01). Conclusion Conclusion. In IBD pts with long disease duration and the presence of extraintestinal manifestations, structural (erosion, enthesophytes) changes in enthesis were observed significantly more often. The frequency of entheses erosions was higher in the presence of pain in the joints, and the number of erosions with vascularization with an increase in laboratory markers of inflammation (CRP).