Objective To observe the protective effect of sodium hyaluronate (Na-HA),and its effects on mRNA expression of peroxisome proliferators-activated receptor gamma (PPAR-γ) in cartilage of rabbit osteoarthritis (OA) model.Methods Forty eight white rabbits were divided into A,B,C groups randomly.Group A were normal controls,groups B and C were underwent unilateral anterior cruciate ligament transection (ACLT).The rabbits in group B were injected normal saline after ACLT;Group C rabbits received intra-articular 1% sodium hyaluronate (HA) injections 5 weeks after surgery,0.3 ml once a week.At week 11 after the surgery,all rabbits were sacrificed.The cartilage changes on the medial femoral condyles were graded.Cartilage sections were stained with safranin-O and HE,mRNA expression of PPAR-γ was detected by real time polymerase chain reaction (Real Time-PCR).Results Cartilage degeneration in group B was significantly more severe than in groups A and C.The grey value of Safranin-O of B group were higher than groups A and C.Expression of PPAR-γ mRNA in group B was higher than that in groups A and C.Conclusion NaHA has a protective effect on articular cartilage degeneration,and the inhibitory effect on PPAR-γ mRNA expression may be one of the therapeutic mechanism of Na-HA.