Musculoskeletal ultrasound assessment in pediatric knee hypermobility: a case control study

BACKGROUND: While musculoskeletal ultrasound (MSUS) use in pediatric rheumatology is becoming more common, the majority of pediatric MSUS literature continues to focus on ultrasound findings in healthy children and juvenile idiopathic arthritis with little discussion of other musculoskeletal problems that may mimic arthritis such as joint hypermobility. Chronic joint pain related to hypermobility is a common referral to pediatric rheumatology clinics. Our aim is to describe the musculoskeletal ultrasound (MSUS) characteristics of the knee in a population with joint hypermobility and pain in comparison to control participants. METHODS: Participants were recruited into three groups for a case-control study. Case group participants had knee hypermobility and pain symptoms (H + P). Participants in one control group had knee hypermobility without pain symptoms (H-P), and participants in the other control group had no knee hypermobility or pain symptoms (NP). B-mode and Doppler MSUS images were obtained and scored for each knee. Descriptive statistics are used for demographic variables and MSUS findings. Regression analysis is used to evaluate risk of synovial effusion and higher synovial effusion/hypertrophy quantitative score. RESULTS: MSUS assessment was performed on 91 knees of 50 participants. H + P knees were more likely to have positive findings noted on MSUS (94% vs. 70% of H-P and 74% of NP knees, p = 0.043). Patellar tendon hyperemia was more common in H + P knees (52%, vs. 19% among H-P and 23% among NP, p = 0.025). Participants who reported taking scheduled non-steroidal anti-inflammatory drugs (NSAIDs) had an increased risk of synovial effusion (RR = 1.83, 95% CI = 1.07–2.30, p = 0.026) and a trend towards increased risk of a higher synovial effusion/hypertrophy quantitative score (RR = 1.77, 95% CI = 0.92–3.38, p = 0.086). CONCLUSIONS: While positive MSUS findings were frequent in all participants, patellar tendon hyperemia was more frequent in participants with knee hypermobility and pain symptoms. Additionally, reported use of NSAIDs was associated with an increased risk of synovial effusion and higher synovial effusion/hypertrophy quantitative score. Further study should assess correlation between tendon abnormalities and degree of pain symptoms as well as the effect of NSAIDs on MSUS findings.