The muscle strength of the lower extremity including hip flexor/extensor, knee flexor/extensor, and ankle plantar flexor/dorsiflexor were tested by HUMAC NORM system (CSMi, U.S.A.) with the mode of concentric/concentric contraction at the angular velocity of 60 degree/s.

Body composition was assessed using an eight-polar tactile-electrode impedance meter (InBody 720; Biospace, Seoul, Korea), which simultaneously recorded bodyweight, total body fat mass, total body muscle mass, lean body mass, bone mineral content and basal metabolic rate.

Quadriceps and hamstrings EMG amplitudes were assessed during walking with stand phase using surface electromyography (EMG) sampled at 1000 Hz (BioNomadix, BIOPAC systems, Inc, Goleta, CA) with electrodes placed over the vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF) and biceps femoris (BF).

Include: single leg vertical hop, Single leg forward one-step hop, Single leg three-step hop, single leg three-step crossover hop. Record hop height, distance and completion of action time.

Fitness of all subjects was evaluated using the HELMAS Physical Fitness Management System (Seoul, Korea). Several dimensions of health-related fitness were evaluated, including muscular strength (grip strength and back strength); balance (closed-eye foot balance); cardiorespiratory endurance (step test); flexibility (sitting trunk flexion and trunk extension); muscle endurance (sit-ups); and agility (reaction time and side steps).

The Marx activity rating scales is a patient-reported instrument. Contrary to the construction of activity level in the Tegner, which is based on participation in specific work and sports activities, activity level of the Marx is determined by measuring some components of physical function that are common to the most sporting activities.

SF-36 consists of eight scaled scores, which are the weighted sums of the questions in their section. Each scale is directly transformed into a 0-100 scale on the assumption that each question carries equal weight. The lower score the more disability. The higher the score the less disability. Eight sections including physical function, role limitation due to physical problems, bodily pain, general health, vitality, social functioning, role limitation due to emotional problems, and mental health. Additionally, the eight health domains can be used to provide a physical component summary and mental component summary score.

KOOS contains 5 subscales with a total of 42 items: 1) pain, 2) other symptoms, 3) function in daily living (ADL), 4) function in sport and recreation and 5) knee-related quality of life. Each question receives a score from 0 to 4 and the scores are transformed to a 0-100 score (0, extreme symptoms, 100, no symptoms). The User's Guide, is available from www.koos.nu.