T1ρ mapping with quantitative biochemical measurements of proteoglycan provides non-invasive means of detecting early composition changes in cartilage degeneration prior to morphological or clinical changes.^1,2 T1ρ mapping have been used to study cartilage changes of confirmed osteoarthritis (OA), but not any studies of undiagnosed OA. The characteristics of cartilage degeneration in early OA patients with knee-joint pain alone in vivo using T1ρ measurements not previously been evaluated. The purpose of this study was to investigate the association of T1ρ relaxation times of the knee with early degenerative cartilage changes, and detect subtle pathological course related to early OA. We included 5 age-matched healthy volunteers and 17 patients (10 male, 7 female age = 25.88 ±1.92 years) who had knee-joint pain without evidence of OA according to their Kellgrene Lawrence (KL) score of 0. Subjects were excluded if they had any performance of cartilage degeneration judged by routine MRI including T1WI and T2WI sequences. The control volunteers had no history of diagnosed OA, clinical OA symptoms, previous knee injuries, or signs of OA on radiographs or/and routine MRI. All images were acquired on a 3.0T MR scanner (Ingenia, Philips Healthcare, Best, the Netherlands) using a 16-channel flexible wrap-around coil. The T1ρ sequences had the following parameters: FOV=140×140, matrix 352x350, slice thickness=4mm, number of slices: 20 slices, TSL=[0,10,20,30,40,ms], spin lock frequency=1700Hz, TE=[0 0,3.4,6.8,10.3,20.5,34.2,47.8,61.5ms], TR/TE=7/3ms, B1=11.5μT, TFE factor=64, Scantime=2:25/SL. The T1ρ map was generated on a pixel-by-pixel basis on Philips Research Integrated Development Environment (PRIDE) software written in Interactive Data Language using a mono-exponential decay model: M (TSL) = M0*exp (-TSL/ T1ρ). Cartilage was segmented into the following compartments: lateral/medial femoral condyle (LFC/MFC), lateral/medial tibia (LT/MT), lateral/medial trochlea (LTRO/MTRO) and patella (PAT), and subcompartments of femoral-tibial cartilage were defined as shown in Figure 1. T1ρ values in different compartments were compared using one-way analysis of variance (ANOVA), and for T1ρ values differences between the two groups in the same compartment were compared with t- test by using IBM SPSS Statistics 20 .0 (Armonk, New York, USA) where P<0.05 indicated a significant difference.There were significant differences in T1ρ values among all the compartments in the joint-pain group (F=2.572, P=0.001). No significant differences in T1ρ values were observed among all the compartments in the control group (f=0.468, P=0.954). In the joint-pain group, there were significant differences in T1ρ values among medial femoral (MF) compartments, including MFC and MTRO (F=9.468, P=0.000), but no significant differences among lateral femoral (LF) compartment were found, including LFC and LTRO (F=2.193, P=0.77). T1r values were significantly higher in the cMFc (weight-bearing cartilage) compartments compared to the other compartments in MF (MTRO, cMFa, cMFp, pMF). There was no significant differences among compartments in MT (F=0.525, P=0.595) and LT (F=1.007, P=0.373). T1ρ values were significantly higher in all compartments except two compartments (cLFa and LTa) in the joint-pain group compared to the control group (table 1, Figure 2).In our study, T1ρ values were significantly higher in most part of the cartilage in knee joint with pain alone even before the morphological changes suggesting proteoglycan loss in human articular cartilage occur in a very early stage. The knee joint-pain suggesting early cartilage degeneration has been occurred even without abnormality in routine MR. The significant differences in T1ρ values among all the compartments in the joint-pain group indicated that the degree of cartilage degeneration in different part of knee joint was uneven, and the control group without loss of proteoglycans had no significant differences in T1ρ values in the total knee joint. There were no significantly differences for T1ρ values in cLFa and LTa between knee joint-pain and control group, this may result from less weight-bearing in cLFa and LTa, and cMFc the main weight-bearing cartilage in medial femoral shows higher T1ρ values.³⁴T1ρ relaxation times are significantly elevated among patients with knee joint-pain compared to the one in normal controls. In this study, we have demonstrated that proteoglycan was reduced in patients with knee joint-pain as the only clinical manifestation. Comparing to routine MR, T1rho mapping sequence may be more useful for the assessment of cartilage degeneration in patients with knee joint-pain alone.