Objective To investigate the role of β-catenin in pathogenesis and progression of knee primaryosteoarthritis (OA) by detecting the expression of β-catenin. Methods Between October 2010 and May 2011, 40 cartilagespecimens were collected from adult knee primary OA patients undergoing total knee arthroplasty and 10 cartilage specimensfrom adult patients suffering from amputation and femoral condylar fracture. All cartilage samples were taken out from femoralcondylar. The decalcified paraffin-embedded sections were prepared and stained with fast green-safranin O to observe thedegeneration of cartilage, then the modified Mankin scale was used to classify the degeneration. The expression of β-cateninwas detected by the immunohistochemistry staining and Western blot. Results According to the Mankin scale, 10 caseshad normal cartilage, 12 had mild degenerative cartilage, and 28 had moderate to severe degenerative cartilage. The histologicalobservation showed the mild degenerative cartilage characterized by fissures in the superficial zone of the articular cartilage,decreased chondrocytes, arrangement disorder, and duplicated tidemark; and the moderate to severe degenerative cartilagecharacterized by fissures in the deep zone of the articular cartilage, obviously decreased chondrocytes and cluster, and even fullthicknesscartilage defect. The β-catenin did not expressed in normal articular cartilage; but it expressed in the degenerativecartilage, and the expression was significantly higher in the moderate to severe degenerative cartilage than in mild degenerativecartilage (P lt; 0.05). Conclusion β-catenin plays a significant role in the pathogenesis and progression of knee primary OA,and the mechanism may be the activation of Wnt/β-catenin signaling pathway, which promotes transcri ption of inflammatorygenes and leads to the destruction of articular cartilage.