What causes weak thigh, hamstring, and gluteal muscles in older people?

Natural history: Gait analysis studies show thigh (quad muscle) inhibition and weakness as we age. It is a natural cause of limping (or knee hyperextended walking), which aggravates the hamstring tendons. Exercises to retrain the quad muscles can help. These exercises include straight leg raises, exercise bicycle, and gentle stairclimbing. Forcing yourself not to limp will also help.