Arthritis Care & Research Vol. 69, No. 10, October 2017, pp 1519–1525 DOI 10.1002/acr.23180 V C 2016, American College of Rheumatology ORIGINAL ARTICLE Ultrasound Features of the Posterior Tibialis Tendon and Peroneus Brevis Tendon Entheses: Comparison Study Between Healthy Adults and Those With Inflammatory Arthritis IAN M. WARD, 1 EUGENE KISSIN, 2 GURJIT KAELEY, 3 JOSHUA N. SCOTT, 4 MICHELLE NEWKIRK, 1 BERNARD A. HILDEBRAND, 1 JOSH LOSPINOSO, 5 MINNA J. KOHLER, 6 AND JAY B. HIGGS 1 Objective. Limited literature exists on the sonographic appearance of the posterior tibialis tendon (PTT) and the peroneus brevis tendon (PBT) entheses. We determined the anatomic features and best imaging techniques of normal PTT and PBT using musculoskeletal ultrasound and compared these findings to subjects with inflammatory arthritis. Methods. Adult subjects were enrolled as healthy controls (HCs), rheumatoid arthritis (RA) patients, or spondyloar- thropathy (SpA) patients. Bilateral PTT and PBT entheses were imaged longitudinally, comparing 2 angles of insonation: perpendicular to the skin surface and 458 cephalad. Images were scored on semiquantitative scales assessing pathology. Results. A total of 78 subjects were enrolled (37 HC, 21 RA, and 20 SpA). Complete enthesis visualization was achieved more frequently in the perpendicular than in the cephalad view for the PBT (76.3% versus 58.7%), but more frequently in the cephalad view for the PTT (58.0% versus 19.6%). RA and SpA subjects had higher rates of PTT fiber disruption (P < 0.001), PTT tenosynovial effusion (P < 0.001), and Doppler signal (P < 0.001) than HCs. No significant differences existed at the PBT enthesis. In multivariate analysis, RA and SpA subjects were found to be 5.1 times (P < 0.001) and 3.6 times (P < 0.001) more likely to exhibit ultrasound-detected pathology, respectively, than HCs. Conclusion. The perpendicular transducer aim is optimal for imaging the PBT, while the cephalad transducer orienta- tion was more effective for evaluation of the PTT. Unlike distal PBT imaging, PTT imaging distinguished healthy and disease states, with both RA and SpA patients showing features of PTT enthesopathy. Distal PTT imaging is a useful technique for musculoskeletal ultrasound. INTRODUCTION Since the utility of ultrasound for anatomic description was first revealed in 1958, the field of musculoskeletal ultrasound has grown significantly (1,2). Musculoskeletal ultrasound provides timely information and has a positive cost/benefit ratio over magnetic resonance imaging in the assessment of common musculoskeletal symptoms (3). Its use as a bedside diagnostic imaging modality has been embraced by the majority of rheumatologic societies, and the American College of Rheumatology specifically recommends the use of ultrasound for the assessment of enthesopathy and tendinopathy (4,5). Approximately 90% of patients with rheumatoid arthri- tis (RA) will report foot-related symptoms at some time during the disease course, and the midfoot appears to be involved more frequently than the ankle (6). While not a classic feature of RA, enthesitis may be an underrecognized The contents of this article are solely the responsibility of the authors and do not necessarily reflect the official views of the Brooke Army Medical Center, the US Army Medical Department, the US Army Office of the Surgeon General, the Department of the Army, or the Department of Defense or the US Government. 1 Ian M. Ward, MD, Michelle Newkirk, DO, Bernard A. Hildebrand, MD, Jay B. Higgs, MD: San Antonio Uniformed Services Health Education Consortium, Fort Sam Houston, Texas; 2 Eugene Kissin, MD: Boston University School of Medi- cine, Boston, Massachusetts; 3 Gurjit Kaeley, MD: University of Florida College of Medicine, Jacksonville; 4 Joshua N. Scott, DO: Wright Patterson Medical Center, Wright Patterson Air Force Base, Ohio; 5 Josh Lospinoso, PhD: Portia Statistical Consulting LLC, San Antonio, Texas; 6 Minna J. Kohler, MD: Massachusetts General Hospital and Harvard Medical School, Boston. Address correspondence to Ian M. Ward, MD, Rheuma- tology Service, Landstuhl Regional Medical Center, CMR 402, Box 2107, APO, AE 09180. E-mail: ian.m.ward.mil@ mail.mil. Submitted for publication July 7, 2016; accepted in revised form December 13, 2016. 1519