Background Kinesiophobia is an excessive, irrational and debilitating fear of physical movement and activity resulting from a feeling of vulnerability to painful injury or re-injury. The Tampa Scale for kinesiophobia (TSK) is a patient-reported outcome (PRO) measure designed to help identify kinesiophobia. The original version of the TSK had 17 items. A 13-item version was later found to have better psychometric properties and was used in the present study. Although the TSK-13 has been widely studied, one shortcoming is the lack of clinically meaningful score categories. The objective of the present study was to develop severity levels to help aid clinical interpretation of TSK-13 scores. Methods After creating four proposed TSK-13 severity ranges, a sample of chronic musculoskeletal pain disorder (CMPD) patients (N = 912) was grouped by TSK-13 scores into: Subclinical (score = 13-22, n = 100; 11%), mild (23-32, n = 271; 30%), moderate (33-42, n = 385; 42%) and severe (43-52, n = 156; 17%) levels of kinesiophobia. These severity groups were then validated by their associations with objective lifting performance (presumed to be highly related to one's level of kinesiophobia) and other PRO questionnaires, assessing depressive symptoms, pain intensity, pain-related anxiety and perceived disability, which all have been shown in previous research to be associated with TSK scores. Results The TSK-13 severity level groups were significantly associated with all lifting performance and PRO variables (p < 0.001). As TSK-13 severity levels increased, lifting performance decreased, while pain intensity, depressive symptoms, pain-related anxiety and perceived disability increased. Conclusions TSK-13 severity levels were strongly associated with objective lifting performance variables and psychosocial PRO measures, providing support for these severity levels as a guideline for healthcare providers and researchers in interpreting TSK-13 scores.