Counting the number of tender and swollen joints is an important aspect of assessing patients with an inflammatory arthritis. We provide a comprehensive overview of joint counts in inflammatory arthritis. This spans how they are undertaken, their use in clinical and research settings, their limitations and standardisation and who can perform them.
We reviewed the literature surrounding joint counts in inflammatory arthropathies, with a specific focus on rheumatoid arthritis (RA).
The current widely used joint count assesses 28 peripheral joints. In RA these are usually incorporated in a composite score of disease activity, termed the disease activity score on a 28-joint count (DAS28). Assessing 28 joints has a strong 'floor-effect' with most patients in routine practice having low swollen and tender joint counts. Marked between-observer variation exists in joint count scores; although the variation in tender joint counts can be reduced by standardised training its impact on swollen joint counts is uncertain. Fibromyalgia can have a marked impact on tender joint count scores, resulting in a disproportionately high tender joint count to swollen joint count ratio. Although there is evidence that patient-assessed tender joint counts correlate well with those undertaken by physicians, patients are limited assessors of synovitis.
Although joint counts provide an important objective measure of disease activity in clinical practice, they have a number of limitations. Future research may provide a more robust clinical assessment for disease activity in inflammatory arthropathies, which overcomes these issues.