Purpose To examine the performance of the PROMIS Upper Extremity Function CAT relative to the PROMIS Physical Function CAT in patients seeking specialty care for upper extremity conditions. Methods This observational trial analyzed prospectively collected PROMIS Upper Extremity and Physical Function CAT scores from 5202 adult patients with 10344 outpatient clinic visits presenting to a tertiary orthopaedic clinic. Pearson’s correlation coefficient was utilized to evaluate the association between initial Physical Function and Upper Extremity scores, as well as the association between changes in Physical Function and Upper Extremity scores between visits. Differences in scores between populations presenting with hand conditions versus shoulder and elbow conditions were evaluated via Student’s t test, as were differences in scores between new and return patient visits. Results PROMIS Upper Extremity CAT scores were strongly correlated with PROMIS Physical Function CAT scores. However, patients averaged 8 points lower scoring on Upper Extremity CAT testing compared to Physical Function CAT scores. The Upper Extremity CAT demonstrated a ceiling effect at a score of 56 that impacted 7% of patients with a secondary ceiling at 50. Change in Physical Function and Upper Extremity scores between visits were moderately correlated with a mean difference of less than 1 point. Patients presenting for hand conditions achieved better Physical Function and Upper Extremity scores than patients presenting for shoulder and elbow conditions. Conclusions The PROMIS Upper Extremity module appears responsive to changes over time. However, the current Upper Extremity CAT has a ceiling score of 56 which does not allow for improvement of scores 0.6 SD higher than the presumptive normative population mean of 50. Although a specific assessment of upper extremity function is desirable, continued refinement of the PROMIS Upper Extremity CAT is required to better assess patients with higher levels of function.