“…OA has been defined by the American College of Rheumatology (ACR) as a 'heterogeneous group of conditions that leads to joint symptoms and signs which are associated with defective integrity of articular cartilage, in addition to related changes in the underlying bone at the joint margins'. It remains an open question whether the initial changes take place in cartilage or bone or other articular tissues and, more importantly, what the causal relationship between these changes is (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) narrowing; JSW, joint space width; K, knee; KLG, Kellgren Lawrence grade; KOSS, knee osteoarthritis scoring system; LF, lateral femoral condyle; LT, lateral tibia; MRI, magnetic resonance imaging; MF, medial femoral condyle; MT, medial tibia; OA, osteoarthritis; OAI, Osteoarthritis Initiative; P, patella; PGs, proteoglycans; pLF, posterior aspect of the lateral femoral condyle; pMF, posterior aspect of the medial femoral condyle; qMRI, quantitative magnetic resonance imaging; SNR, signalto-noise ratio; SPGR, spoiled gradient echo; SSFP,steady-state free precession; T, tibia; T 1 , longitudinal relaxation time; T 1rho , T 1 in the rotating frame; T 2 , transverse relaxation time; tAB, total area of subchondral bone; ThC, thickness of the cartilage; ThCcAB, thickness of the cartilage, summarized over cAB (without including denuded areas as 0 mm cartilage thickness); ThCtAB, thickness of the cartilage, summarized over tAB (including denuded areas as 0 mm cartilage thickness); TKA, total knee arthroplasty; TrF, trochlear of femur; VC, volume of cartilage; VctAB, volume of cartilage normalized to the total area of subchondral bone (tAB); we, water excitation; WOMAC, Western Ontario McMaster University-Index; WORMS, whole-organ MRI score; mCT, micro-computed tomography.…”