Knee pain as a reason for referral to a paediatric rheumatologist: A retrospective study

Knee pain is the most frequently reported type of lower extremity pain among children and adolescents. The objective of this study was to establish the features distinguishing inflammatory knee pain from non-inflammatory knee pain and to determine the specific variables to consider in suspected juvenile idiopathic arthritis (JIA).

A retrospective chart review was performed among children with knee pain evaluated through paediatric rheumatology consultations at a single centre between 2012 and 2019.

Among the 262 children, 32 patients (12.2%) were diagnosed with JIA, 46 patients (17.6%) presented with inflammatory knee pain (IP) of an origin different than JIA, and 57 patients (21.7%) with non-inflammatory knee pain (NIP). In 127 cases (48.5%), no musculoskeletal disorder was diagnosed (NDD). The presence of limping, joint swelling, decreased passive range of motion and decreased active range of motion of the knee joint were registered more frequently in the JIA group compared to the other three groups. Multivariate analysis showed that a family history of autoimmune diseases and pain in other joints were associated with inflammatory pain. Increased pain after physical activity, pain only in the knee joint and absence of limping were predictors of NIP. The risk factors of JIA were limping and an erythrocyte sedimentation range of ≥10 mm after an hour. In the NDD group, the risk factors included no increase in pain after physical activity, serum C-reactive protein level < 5 mg/L and normal musculoskeletal ultrasound image.

The majority of children with knee pain referred to a paediatric rheumatologist do not have arthritis. Knee pain alone, as a chief complaint, rarely leads to a final JIA diagnosis. Further studies are necessary in order to design the appropriate diagnostic and therapeutic algorithms.