The most frequent late symptom of untreated Lyme disease in the United States is inflammatory arthritis. While antimicrobial treatment is effective in reducing swelling and discomfort in 90% of patients, many people experience residual inflammation, which is referred to as post-infectious Lyme arthritis (PILA). Current Lyme arthritis outcome metrics have numerous limitations, as improvement is considered a binary outcome based purely on physical examination. There was increased interest in using ultrasonography to better identify outcomes in inflammatory arthritis, which is especially important for monoarticular or oligoarticular disorders such as late Lyme arthritis and PILA. For a study, researchers presented the findings of a group of 5 patients who had ultrasonography assessments that led to a diagnosis of PILA. 

It was a case study of 5 patients with PILA who were referred for examination and treatment of troublesome joints. Even in patients with minor clinical signs, musculoskeletal ultrasonography revealed the substantial joint disease. Synovitis, effusions, enthesitis/tendinopathy, and bone erosions were seen, confirming the existence of active inflammatory arthritis. In certain patients with PILA, there was a significant inflammatory change, including synovitis, enthesitis, and erosions. Systematic sonographic examination of patients with PILA was required to further assess pathology and therapy response.