Soreness and weakness of the calves below the knee may be caused by overwork. Such as long hours of heavy physical labor or strenuous sports, caused by lower limb muscle fatigue, there may be symptoms of calf weakness. In addition, soreness and weakness of the calves may be caused by hypokalemic periodic paralysis. Patients suffering from hypokalemic periodic paralysis may have muscle weakness of the limbs. Many patients have weakness of both lower limbs as the first symptom when they sleep at night or wake up in the early morning, and in severe cases, it may cause respiratory problems. In addition, patients with Guillain-Barre syndrome, myasthenia gravis or hypothyroidism may experience weakness in the calves. In this case, it is important to rest and avoid exertion. If accompanied by other symptoms, you need to go to the hospital for further examination, in order to clarify the diagnosis, and according to the cause of the disease for targeted treatment.