Background: Knee osteoarthritis is a common chronic degenerative disease resulting in joint histopathologic and serologic changes. TGF-β and VEGF change have a close relationship with knee osteoarthritis. Objective: To evaluate the expression of Transforming Growth Factor (TGF)-β and Vascular Endothelial Growth Factor (VEGF) in patients with and without knee Osteoarthritis (OA) and to assess the clinical relevance between these expressions and knee OA. Design: Case-control study. Setting: Hospital. Methods: We collected pathological knee synovial tissue from 50 patients with OA. We evaluated TGF-β and VEGF expressions of synovial tissue using immunohistochemical methods. The χ2 test was used for statistical analysis. Participants: Patients with and without knee OA were compared. We divided patients with OA into mild, moderate, and severe groups (n=50 per group). The control group included 50 patients without arthritis. Results: We found inflammatory infiltrates, synovial cell hyperplasia, significant blood capillary hyperplasia, fiber hyperplasia around the capillaries, and disordered arrangement of cartilage cells in the synovial tissue of patients with OA. TGF-β expression increased in patients with the degree of knee synovial tissue with OA; the increased VEGF expression correlated with blood capillary hyperplasia and inflammatory infiltrates. TGF-β and VEGF expressions were significantly different between the control and severe groups (P<0.01). There was no obvious difference between the control and mild groups, mild and moderate groups, and moderate and severe groups. TGF-β and VEGF expressions had a significant positive correlation (r=0.783; P<0.05). Conclusion: TGF-β and VEGF expressions are related to the degree of synovial lesions of knee joints with OA; thus, they can be regarded as an indicator of knee OA.