Background/Purpose: Lyme arthritis (LA), the most common late manifestation of Lyme disease, usually occurs months to up to 2 years after the initial infection. Joint involvement is characterized by proliferative synovitis predominantly affecting the knees. Most patients respond to antibiotic treatment, but a subset have persistent inflammatory arthritis despite resolution of the infection and others may have continued pain despite resolution of synovitis on examination. It is unclear why arthritis onset is delayed after initial spirochetal infection and hematogenous dissemination. It has been postulated that prior to clinical synovitis, less well-vascularized tissues such as tendons or ligaments may harbor spirochetes. Imaging studies, such as ultrasound (US) may offer further insights, however information is limited about US characteristics of Lyme arthritis.

Methods: We retrospectively reviewed images and clinical characteristics of adult LA patients who underwent musculoskeletal US examinations of the knee joints in the Rheumatology Clinic at Massachusetts General Hospital. Examinations were included when complete diagnostic examination was performed (including longitudinal and transverse suprapatellar views, medial and lateral longitudinal views, posterior transverse and longitudinal views). All LA patients met the diagnostic criteria of the Centers for Disease Control and Prevention (CDC) for Lyme disease. Images from control subjects with osteoarthritis were reviewed as a comparison group. All images were reviewed by 2 ultrasound-trained rheumatologists with inter-reader agreement.

Results: Forty-nine knee examinations were reviewed in 31 individual LA patients. The median age of the patients was 52, and 18 of the 31 patients (58%) were male. Of the LA patients, the majority, 24, had arthritis which was refractory to oral and IV antibiotic treatment, while 7 had arthritis which was responsive to oral or IV antibiotic treatment. The median semi-quantitative synovitis score was 2 (range 0 to 3). Effusion was seen in 67% of examinations and presence of a Baker’s cyst was observed in one-quarter of examinations. Presence of radiographic erosion was observed in only one patient. Of the 31 patients, 28 (90%) were found to have abnormalities in posterior knee tendons, most commonly the semimembranosus, and less frequently the semitendinosus, tendons. These abnormalities included hyperechoic deposits with tendinopathy and tenosynovitis. Abnormalities were rarely seen in other tendons and were not seen in control subjects. In several patients who had serial examinations, the tendon abnormalities persisted although synovitis measures improved.

Conclusion: It has not been previously recognized that hamstring tendons are commonly affected in LA. Calcific tendinitis and tendinopathy may contribute to the persistence of knee pain in some LA patients despite resolution of synovial inflammation. Further, evidence of calcification suggests that tendons may be a prior site of B. burgdorferi infection. As a privileged site, tendons may initially allow protection of spirochetes from the immune system and may contribute to seeding of synovium later in the disease.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/ultrasonographic-examinations-show-highly-prevalent-abnormalities-of-hamstring-tendons-in-lyme-arthritis-patients/