Previous studies have shown higher T2 and T1rho values of knee cartilage in OA patients compared to healthy controls, and the evidence that those values are correlated with the severity of OA (1). However, we often observe signal heterogeneity with mixed high and low signal of early cartilage degeneration, which has been classified as grade 1 cartilage lesion in Outerbridge’s classification (2). The purpose of this study was to assess patterns of T2 and T1rho value change with grade 1 lesions in OA patients compared to healthy control cartilage, thereby elucidating the efficacy of T2 and T1rho measurements in detecting early cartilage degeneration.A total of 45 knees from 43 subjects were enrolled in this study. Twenty knees from 20 healthy volunteers (mean age 28.9 years, 13 men and 7 women) were included as a control group (3, 4). Twenty-five knees from 23 OA patients (mean age 53.6 years, 10 men and 23 women) were examined, including 18 early OA patients (Kellgren-Lawrence (KL) 1 or 2) and 5 advanced OA patients (KL 3 or 4) scheduled for total knee arthroplasty. Three sagittal images were acquired on a 3T scanner (Achieva, Philips Healthcare, Netherlands) with an 8-channel knee coil, including fat suppressed (FS) proton density-weighted imaging (PDWI) sequence (TR/TE, 4311/30ms; FOV/slice thickness/gap=140/3/0mm, matrix size=512×512), T2 mapping sequence (TR/TE= 2700/13, 26, 39, 52, 65, 78, 91ms, FA=90, FOV/slice thickness/gap= 140/3/0mm, matrix size=512×512), and T1rho mapping sequence using spoiled gradient echo (SPGR, TR/TE= 6.4/3.4ms, FA=10, FOV/slice thickness/gap= 140/3/0mm, matrix size=512×512, time of spin lock, 20, 40, 60, and 80ms), with true sagittal angulation, parallel to the magnetic static field (B0). Manual segmentation of entire femoral cartilage was performed slice by slice using Matlab (Mathworks, Natick, MA, Figure 1). The center of the medial condyle (MC), lateral condyle (LC), and trochlea (T) were defined by referring to reformatted coronal images. Then we converted a total of 31 slices into 23 normalized slices in each subject, based on three anatomical landmarks by every 3-mm slice thickness (e.g. MC+3, MC+6, T-3). We calculated the average T2 and T1rho values at each normalized slice in both deep and superficial layer with 4-degree stepwise analysis. Then we created excel spreadsheets of T2 and T1rho values of each layer in each OA patients. Normal T2 and T1rho spreadsheets created in our previous study were used as a control (3, 4). Areas of signal heterogeneity within cartilage of the distal femur were identified using FS PDW images. Slice number and angle with respect to B0 (e.g. slice 10-12, angle 22-58°) were recorded and corresponding T2 and T1rho value were calculated. In addition to simple grade 1 lesions, grade 2 lesions (partial thickness defect≦50%) and grade 3 lesions (partial thickness defect > 50%) including grade 1 lesions were also evaluated and classified as grade 1-2 and grade 1-3, respectively. T2 and T1rho values with early cartilage degeneration in OA patients were compared to those of corresponding areas of normalized slices and angles in healthy subjects. The comparison was made in each superficial and deep layer. A total of 28 cartilage degeneration (22/6 lesions with early/advanced OA) were identified. Cartilage with signal heterogeneity from the entire OA patients demonstrated higher T2 and T1rho values than corresponding areas of cartilage from healthy subjects in each deep and superficial layer without statistical significance (Figure 2). However, when they were divided into early OA and advanced OA, there was no obvious tendency of higher cartilage T2 and T1rho values in early OA patients over healthy subjects, while tendency to higher cartilage T2 and T1rho in advanced OA was clearly seen without statistical significance (Figure 3). Table 1 shows conceivable patterns of change in T2 and T1rho values between normal and OA subjects in each deep and superficial layer. Many grade 1 lesions with signal heterogeneity demonstrated either statistically no significant change or significant increase in T2 and T1rho values compared to normal cartilage (18/28 (64%) in T2 and 23/28 (82%) in T1rho). Compared to T2 values, T1rho values are more sensitive for detecting a typical pattern of significant higher values in OA patients than the normal control in both deep and superficial layers (Table 1). However, T2 and T1rho values in grade 1 cartilage degeneration can be lower compared to those in healthy cartilage (Table 1, Figure 4). These findings suggest grade 1 cartilage lesions demonstrate various patterns of T2 and T1rho changes.