Objective To study the appearance of MR diffusion weighted imaging in early stages of cartilage degeneration and to detect its values. Methods In 20 goat left knees, intra- articular injection of 5 units of papain was performed causing a loss of cartilage proteoglycan. Twenty right knees were used as control group. MR diffusion weighted imaging was performed at 24 hours after intra-articular injection of papain. ADC of each part of articular cartilage was measured and compared with each other. The proteoglycan content was measured biochemically and histochemicaUy. Routine MRI and DWI were performed in 100 patients with osteoarthritis and 20 healthy people. The ADC of each interested part of articular cartilage was measured and compared with each other. Results In experimental control group, the ADCav of articular cartilage was (14.2±2.3)×10-4 mm2/s. In early stages of cartilage degeneration group, the ADCav of articular cartilage was (17.5±4.2) × 10-4 mm2/s. The ADCav of the control group was lower than that of the early stages of cartilage degeneration group (t = 2.709 ; P = 0.016) . The proteloglyean content of articular cartilage was 4.22×10<'6> μg/kg in control group, and 0.82×10<'6>μg/kg in experimental group at 24 hours after injection of papain. The difference between control group and experimental group was significant (t = 2.705, P = 0.018). In healthy people, the ADCav of articular cartilage was (7.6±2. 2) × 10-4 mm2/s. In osteoarthritis group, the ADCav of articular cartilage was (10.3±4. 2) × 10-4 mm2/s. The ADCav in the healthy group was significantly lower than that in the osteoarthritis group (t = 2.609, P = 0.014). Conclusion DWI is an useful method in detecting early stages of cartilage degeneration which can not be showed on routine sequences.