Minimally invasive total knee arthroplasty (MIS-TKA) became the popular technique. It had the less postoperative pain and shorter recovery time compared to the conventional technique. With using MIS technique, less cut of quadriceps tendon was the key. It related to keep more quadriceps strength and improve functional performance after TKA. However, there was no previous studies about the effect of quadriceps incision length in the recovery time of the quadriceps strength. The investigators hypothesized that longer quadriceps incision affected the longer recovery time of quadriceps strength in MIS-TKA.

Inclusion Criteria:

• The patients who diagnosed primary osteoarthritis of knee with

  1. varus or valgus deformity < 20 degrees
  2. preoperative range of motion > 90 degrees
  3. extension lag < 10 degrees
  4. Flexion contracture < 30 degrees

Exclusion Criteria:

• Bilateral simultaneous total knee arthroplasty
• Previous knee surgery
• Inadequate exposure during the surgery