This prospective, randomized trial asked whether subcutaneous indwelling of vacuum drainage has advantages over intraarticular indwelling in terms of blood loss, bleeding related complications, and functional outcomes in primary total knee arthroplasty (TKA). The investigators hypothesized that the subcutaneous indwelling method would reduce blood loss with comparable bleeding-related complications and functional outcomes. The subcutaneous indwelling group demonstrated reduced blood loss with comparable prevalence of bleeding-related complications and functional outcomes. In conclusion, the investigators' study verified the efficacy and absence of risks of subcutaneous indwelling method. So the investigators propose that the subcutaneous indwelling drainage can be a good option to address the problems related to postoperative bleeding after TKA.

There are numerous reports in the literature on drainage options after TKA, but there is no consensus. Many studies have shown no apparent advantage of drainage but routine intraarticular indwelling drainage after TKA has been extensively used to avoid complications associated with hematoma formation. It is of interest to determine if it is possible to reduce blood loss while still using drainage. So we came to think about a new and more convenient method-subcutaneous indwelling. Theoretically subcutaneous indwelling method which still has the advantages over the intraarticular indwelling method but is more convenient than drain-clamping method may be a better option. So we hypothesized that subcutaneous indwelling method of vacuum drainage has advantages over the intraarticular indwelling method.

Inclusion Criteria:

• Diagnosis of primary osteoarthritis
• primary total knee arthroplasty
• Signed written informed consent
• Spinal/epidural anesthesia

Exclusion Criteria:

• Patients with coagulation disorders
• Revision total knee arthroplasty
• Simultaneous bilateral total knee arthroplasty
• Diagnosis other than primary osteoarthritis
• Patients refusing consents