SAT0578 Patellar tendon enthesisabnormalities and their association with knee pain and structural abnormalities in older adults
Authors: S.M. Mattap, D. Aitken, K. Wills, A. Halliday, C. Ding, W. Han, F. Cicuttini, G. Jones, L. Laslett
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> The patellar tendon works together with the quadriceps tendon to enable knee flexion and straightening. Its attachment site (enthesis) is at risk of micro damage and degeneration. Recent studies suggest that enthesis abnormalities are associated with development of osteoarthritis.<sup>1, 2</sup> However, no studies have assessed the presence of patellar enthesis abnormalities in older adults and its association with osteoarthritis outcomes. <h3>Objectives</h3> To describe the associations of patellar tendon enthesis (PTE) abnormalities visible on magnetic resonance (MR) images; and knee pain, physical function limitations, osteoarthritic structural abnormalities cross-sectionally and longitudinally over 10.7 years. <h3>Methods</h3> PTE abnormalities were defined as presence of abnormal bone signal and/or bone erosion. They were measured on T2-weighted fat suppressed fast spin echo MR images at baseline in 961 community-dwelling older adults and followed for 10.7 years. Knee pain and physical function limitation score were assessed using WOMAC. Bone marrow lesions (BMLs), cartilage volume and defects, tibial bone area, and infrapatellar fat pad (IPFP) area were assessed using validated methods. Associations were assessed using hurdle, log binomial, linear, and mixed models, after adjusting for confounders. <h3>Results</h3> 20% of participants had bone signal and/or erosion at PTE. Cross-sectionally, presence of PTE abnormalities were associated with greater intensity of pain while going up and down stairs (β=0.22 (95% CI; 0.03, 0.41)), greater risk of having a femoral BML (RR=1.46 (1.22, 1.90)), greater lateral tibial bone area (β=25.95 (1.00, 50.91)), smaller IPFP area (β=−0.26 (-0.46,–0.05)), and a worse tibial cartilage defects cross sectionally (RR=1.70 (1.16, 2.47), after adjustment of demographic and structural confounders. Longitudinally, PTE abnormalities at baseline predicted an increased risk of deleterious changes in tibial BML size (RR=1.52 (1.12, 2.05)) but not clinical symptoms, and other structural changes over 10.7 years. <h3>Conclusions</h3> Patellar tendon enthesis abnormalities are common in the elderly. The presence of cross-sectional but not longitudinal associations suggests they commonly co-exist with other knee structural abnormalities, but that they are not be a major player in symptom development or structural changes, excepting tibial BMLs. <h3>References</h3> [1] Binks DA, Bergin D, Freemont AJ, Hodgson RJ, Yonenaga T, McGonagle D, et al. Potential role of the posterior cruciate ligament synovio-entheseal complex in joint effusion in early osteoarthritis: a magnetic resonance imaging and histological evaluation of cadaveric tissue and data from the Osteoarthritis Initiative. Osteoarthritis Cartilage. 2014;22(9):1310–7. [2] Benjamin M, McGonagle D. Histopathologic changes at "synovio-entheseal complexes" suggesting a novel mechanism for synovitis in osteoarthritis and spondylarthritis. Arthritis Rheum2007;56(11):3601–9. <h3>Acknowledgements</h3> National Health and Medical Research Council of Australia; Tasmanian Community Fund; Masonic Centenary Medical Research Foundation. <h3>Disclosure of Interest</h3> None declared