Responsiveness of Subjective and Objective Measures of Pain and Function Following Operative Interventions for Musculoskeletal Conditions: A Narrative Review

Objective: Musculoskeletal (MSK) disorders affect similar to 50% of US adults and 75% of those over the age of 65, representing a sizable economic and disability burden. Outcome measures, both objective and subjective, help clinicians and investigators determine whether interventions to treat MSK conditions are effective. This narrative review qualitatively compared the responsiveness of different types of outcome measures, a key measurement characteristic that assesses an outcome measure's ability to detect change in patient status. Methods: We evaluated elective orthopedic interventions as a model for assessing responsiveness because the great majority of patients improves following surgery. We searched for articles reporting responsiveness (quantified as effect size [ES]) of subjective and objective outcome measures after orthopedic surgery and included 16 articles reporting 17 interventions in this review. Results: In 14 of 17 interventions, subjective function measures had an ES 10% greater than that of objective function measures. Two reported a difference in ES of < 10%. The sole intervention that demonstrated higher ES of objective function used a composite measure. Sixteen interventions reported measures of subjective pain and/or mixed measures and subjective function. In nine interventions, subjective pain had a higher ES than subjective function by > 10%, in three, subjective function had a higher ES than subjective pain by > 10%, and in the remaining four, the difference between pain and function was < 10%. Conclusion: These findings reinforce the clinical observation that subjective pain generally changes more than function following elective orthopedic surgery. They also suggest that subjective function measures are more responsive than objective function measures, and composite scores may be more responsive than individual performance tests.