Pengaruh Terapi Latihan Penguatan Otot Kuadrisep Intensitas Ringan dan Sedang pada Penderita Osteoarthritis Lutut Tinjauan terhadap Kekuatan otot Kuadrisep, Waktu Jalan 15 meter dan Kadar Enzim Kreatin Kinase Serum = Effect Quadriceps Muscle Strengthening Low and Moderate Intensity In Patient With Osteoarthritis Knee Study of Quadriceps Muscle Strength, Confortable Walking Speed 15 meters, and Creatine Kinase Enzyme