One cause of heavy legs is multiple sclerosis, according to WebMD. This is a disorder where the patient's own immune system attacks the myelin sheath of the central nervous system. The patient's leg can feel so heavy and unwieldy that the patient drags it. Peripheral neuropathy can also cause heavy legs, says Healthline.
Multiple sclerosis is an unpredictable disease, and symptoms vary widely from one patient to the next, explains WebMD. Along with heavy legs, the patient may also experience muscles that are weak and stiff, blurry or hazy vision and pain in the eye, and tingling and numbness. The patient may also have problems with balance and may feel lightheaded or dizzy now and again. In some patients, years pass before these symptoms recur.
Peripheral neuropathy happens when damage occurs to the nerves that connect the appendages and other parts of the body to the central nervous system, says Healthline. The symptoms depend on which part of the body the damaged nerves are serving, so they can be very wide-ranging. Besides heavy legs, patients suffer tingling and numbness, stabbing pains, thin skin, sexual dysfunction and problems with digestion. Diseases, infections, alcohol abuse, toxins or injuries can cause peripheral neuropathy.