To compare muscle torque recovery between patients under subvastus approach and those under midvastus approach after total knee replacement

Total knee Arthroplasty is a common operated surgery in each hospitals, and a lots of patients benefit from this surgery. Traditionally the frequently used surgical approach is parapatellar approach. However, recently the subvastus and midvastus approach has gained a world-wide population. These two methods had less damage to the quadriceps tendon and theoretically should have better post-operative muscle power recovery, less lateral retinaculum release because of better patellar tracking. The only differences between these two approaches are that the midvastus approach will split the vastus medialis muscle and denervation may occur. In this study we will use HSS or KSS functional score and Cybex dynamometer to evaluate the functional recovery, and use Merchant's view radiography to evaluate the result of patellar tracking. The follow-up period will not be limited and we will use mixed-model statistic's random effect to gain the natural history of muscle power recovery, which will become the base of other study. We can also compare the difference of results between PS type and CR type and different surgical approach. The natural history of the knee score will also be obtained.

Inclusion Criteria:

• Patients after subvastus approach or midvastus approach total knee replacement

Exclusion Criteria:

• patients with severe hypertension, heart disease or other problems which negatively influence the security of muscle test

Patients after total knee replacement without severe systemic disorders