Glucosamine is an important part of the treatment strategy for osteoarthritis, but its effectiveness is still controversial. To explain the efficacy differences of glucosamine, in this study the investigators detect the concentration of glucosamine in the plasma and synovial fluid, some effect indexes such as inflammatory markers and gene polymorphism of glucosamine transporters. On the one hand, the investigators compare the plasma peak and gluten glucosamine concentration and the concentration in synovial fluid among participants to observe the individual differences of glucosamine exposure in vivo. On the other hand, the investigators investigate the correlation between drug concentrations, effect index and gene polymorphism. The hypothesis is that glucosamine exposure in vivo has individual differences and gene polymorphism can explain this differences.

Inclusion Criteria:

1. patients undergoing total knee arthroplasty for knee osteoarthritis;
2. 60-80 years.

Exclusion Criteria:

1. patients with severe liver or renal insufficiency;
2. patients allergic to glucosamine or any excipients in tablets;
3. patients who have been treated with glucosamine within three months;
4. patients who are unable to cooperate with the study;
5. continuous medication is less than 4 days;
6. patients with diarrhea, vomiting and other adverse reactions during medication.

Patients undergoing total knee arthroplasty for knee osteoarthritis