there are many reasons which causes muscle pain like poor nutrition diet causing easy fatigue, sometimes a compression on the nerve root can result in pain referring to the muscles. The blood vessels supplying the muscle can be distended or might be obstructed due to clot formed in it. People with uncontrolled diabetes can have neuropathy which can cause burning and tingling sensation and may sometimes have leg pain. Apart from these knee joint or ankle join pain can be due age related leading to wear and tear of the cartilage supporting the bone ends and gradual diminishing of the fluid between the bone endings with age. So all this things should be examined properly with the aid of investigations to ascertain a proper cause. So kindly consult a surgeon for further management...for breathing issues consult physicians.