Approximately 20% of patients experience chronic pain after total knee replacement (TKR), yet there is no consensus about how best to assess such pain. This systematic review aimed to identify measures used to characterize chronic pain after TKR.
MEDLINE, Embase, PsycINFO, Cochrane Library, and CINAHL databases were searched for research articles published in all languages from January 2002 to November 2011. Articles were eligible for inclusion if they assessed knee pain at a minimum of 3 months after TKR, yielding a total of 1,164 articles. The data extracted included the study design, country, timings of assessments, and outcome measures containing pain items. The outcome measures were compared with domains recommended by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) for inclusion in the assessment of chronic pain–related outcomes within clinical trials. Temporal trends were also explored.
The review found use of a wide variety of composite and single-item measures, with the American Knee Society Score the most common. Many measures used in published studies did not capture the multidimensional nature of pain recommended by the IMMPACT; of those commonly used, the Western Ontario and McMaster Universities Osteoarthritis Index and Oxford Knee Score were the most comprehensive. Geographic trends were evident, with nation-specific preferences for particular measures. A recent reduction in the use of some clinically administered tools was accompanied by an increased use of patient-reported outcome measures.
There was wide variation in the methods of pain assessment alongside nation-specific preferences and changing temporal trends in pain assessment after TKR. Standardization and improvements in assessment are needed to enhance the quality of research and facilitate the establishment of a core outcome set.