Experimental: Study Group. Elderly participants diagnosed with bilateral KOA will receive complete rehabilitation program (10 sessions of electrotherapy measures - transcutaneous nerve stimulation, ultrasound and low intensity laser treatment; 6 weeks of kinetic measures and gait training). Previous, all participants will be complete gait clinical, ultrasound and functional assess.

Active Comparator: Control Group Control Group will receive only 10 sessions of electrotherapy (transcutaneous nerve stimulation, ultrasound and low intensity laser treatment) and 6 weeks of kinetic measures, without gait control training. Previous, all participants will be complete clinical gait, ultrasound and functional assess.

Ultrasound exam (initial and after 3 months) - with SonoScape S9Pro; the investigators exam the thickness of the quadriceps muscle group between the superficial fat-muscle interface and the cortex of the femur and calculate the quadriceps muscle index as sum of both muscle thickness RT and LT cm/height2 (m2). The exam is conducted by a qualified sonographer. The examination is carried out on a one-on-one basis in a private setting where only the participant and the sonographer are present.

Gait analysis with wireless system - BTS G-WALK; the investigators consider four gait parameters: Timed Up-and-Go (TUG) test, Symmetry index, Six Minutes Walking Test (6 MWT), and Walk cadence or average cadence (steps/min).

Timed Up-and-Go (TUG) test (seconds) - participants stood up from an armed chair, walked at a safe and comfortable pace to a line 3 m away, crossed the line, turned, and returned to a sitting position in the chair; none of the patients used a walking aid and the time to complete the task was recorded.

Six Minutes Walking Test (6 MWT) - "walking distance" (meters) and "average cadence" (steps/minute).

WOMAC scale contains 24 specific questions divided into three domains: pain (P-WOMAC; 5 items), stiffness (S-WOMAC; 2 items) and physical function (PF-WOMAC; 17 items). The score of each question ranges from 0 to 4. The 0 score is equivalent to maximal functional status and high scores 96 indicates a minimum status, with high disruption in day to day tasks.

In ultrasound exam, after establishing the midway point between the tip of the greater trochanter and the lateral joint line of the knee, the investigators identify the muscle tissue; the thickness of the quadriceps muscle (in centimeters) is established by measuring the space between the cortex of the femur and therefore the most superficial muscular fascia. Quadriceps muscle index is calculated as sum of both quadriceps muscle thickness Right and Left centimeters/ participant square height (square meters). Participant is exam with the knee extended.