Abstract: Objective To explore the relationship between angiogenesis and knee osteoarthritis (OA) in rats through micro-CT. Methods Twenty female SD rats were divided into five groups randomly, every group had 4 rats, four groups were experimental groups (16) and one group was sham-operated group (4). Rats in experimental group received resection of left knee anterior cruciate ligament and meniscus, rats in sham-operated group with open joint capsules. Rats were sacrificed at 3 weeks, 6 weeks, 9 weeks and 12 weeks in experimental group. Osteochondral composites of medial tibia were sampled sites. The analysis methods included gross observation, mirco-CT vascular morphology metrology and three dimensional reconstruction of angiogenesis. Results Degeneration of cartilage occurred in experimental group after a week. Osteoarthritis became worse over time. Spotted cartilage appeared at 3 weeks after operation, Tb.Th (0.35±0.21) mm, BMD (29.6±7.2) mg/cm³, BVF (6.1±3.3)%, VVF (0.56±0.24)%. Plate shaped cartilage increased at 6 weeks after operation, Tb.Th (0.24±0.11) mm, BMD (25.7±8.1) mg/cm³, BVF (4.7±1.8)%, VVF(0.71±0.41)%. Cartilage defects of full-thickness can be observed at 9 weeks after operation, Tb.Th (0.11±0.07) mm, BMD (18.5±10.1) mg/cm³, BVF (3.1±2.1)%, VVF (0.82±0.28)%. Osteophyte formation in 12 weeks postoperatively. Tb.Th (0.05±0.01) mm, BMD (41.3±6.9) mg/cm³, BVF (9.1±1.7)%, VVF (0.17±0.12)%. Tb.Th, BMD, BVF and VVF were statistically significant in experimental group compared with sham-operated group (P=0.008). Conclusion Angiogenesis is important in the mechanisms of osteoarthritis. Microvascular hyperplasia reaches a peak in the mid-term of the arthritis.