Background/Purpose: Ligament attachments are often found to form complex anatomical functional units involving the ligaments themselves as well as associated synovium and bony tuberosities. Furthermore, stress minimising accessory fibrocartilages are frequently observed in the immediately adjacent joint cavities. Collectively, these structures are termed synovio-entheseal complexes (SECs) and are subject to the full gamut of degenerative changes associated with the osteoarthritis (OA) disease process.¹ Here we have investigated the SEC formed at the posterior cruciate ligament (PCL) tibial insertion using high resolution magnetic resonance imaging (MRI) and matched histology to show the involvement of the PCL-SEC in the phenotypic expression of knee OA.

Methods: High-resolution 3T MRI and comparative histological evaluation were performed on 14 normal cadaveric knee joints. SEC microanatomy and OA features of the PCL tibial attachment were evaluated on serial histological sections stained with H&E and Masson’s Trichrome. Bilateral 3T MRI images were evaluated in 49 patients with early OA from the Osteoarthritis Initiative cohort for SEC morphology and for lesions associated with the early OA disease process at the PCL tibial enthesis. Differences among groups were determined by calculation of chi-square values.

Results: Histological evaluation confirmed the SEC microanatomical structure comprising the PCL, adjacent tibial bone plateau and intervening synovium along with sesamoid, periosteal and enthesis accessory cartilages and the posterior horn of the medial meniscus. Evidence of microanatomical damage was observed throughout the PCL-SEC, including; neovascularisation, chondrocyte cell clustering, tide mark duplication and mild inflammatory changes. In the early OA cohort, 3T MRI showed a high prevalence of SEC related lesions including bone marrow oedema (BME) immediately anterior to the PCL insertion (seen in 61% of knees) and osteophytosis lateral to the PCL insertion (85%). Signal hyperintensity on fluid sensitive sequences compatible with posterior recess synovitis immediately adjacent to the PCL was seen in 48% of knees and correlated with SEC cartilage abnormality (χ² =7.25, p<0.01) . Furthermore, the frequency of BME at the PCL insertion was associated with a medial meniscus posterior horn deficient SEC anatomical variant (χ² =10.02, p<0.05).    

Conclusion: The PCL has a prominent SEC configuration that is associated with microscopic evidence of OA in normal tissue. In early knee OA, pathological features were commonly observed at the PCL-SEC and immediately adjacent locations on 3T MRI. Although the PCL rarely fails in OA, the PCL-SEC could play a hitherto unappreciated but important role in the phenotypic expression of early knee OA.

References: 1.Benjamin M, McGonagle D. Arthritis & Rheumatism 2007 56:3601-09.

---

« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/anatomical-variation-in-the-morphology-of-the-posterior-cruciate-ligament-synovio-entheseal-complex-and-correlation-with-degenerative-change/