The soreness of the joints may be caused by the following reasons: 1. After prolonged strenuous exercise or heavy physical labor, repeated contraction of muscle tissue and anaerobic enzymes produce large amounts of lactic acid, which cannot be metabolized in time and accumulate in the muscles and bone joints causing soreness; 2. If accompanied by drowsiness, general weakness or fever, most of the symptoms are caused by cold. In patients with rheumatoid rheumatism, the rheumatoid factor attacks the bones and joints and causes redness, swelling, heat and pain in the joints, which can also cause pain in the joints. 4. Symptoms.