Darkening of finger joints may be caused by hyperpigmentation, trauma, vitamin B deficiency, skin diseases and other reasons. 1. Hyperpigmentation: With age, the degeneration of human skin and original tissues can cause hyperpigmentation, resulting in darkening of the finger joints and change of skin color. 2. Trauma: If the soft tissue is damaged, it will lead to the oozing of capillaries under the skin, and the blood will be pooled under the skin, which will lead to the formation of hematoma and also lead to the blackening of the joints. 3. Lack of vitamin B: usually unbalanced diet, vegetables, fruits, soy products intake is relatively small, the body lacks vitamin B, or usually drink a lot of water or a lot of exercise, will also cause excessive consumption of vitamin B in the body, causing water metabolism disorders, blood supply to the joints, lack of oxygen, will lead to joints black skin. 4 skin disease: chronic infection of the skin can cause inflammatory reaction, such as like skin melanin disease can also lead to black finger joints. Finger joints black may also be caused by other reasons, such as drug factors, vascular disease, etc. If you exclude physiological reasons, you can promptly consult a doctor to clarify the specific causes, and if necessary, carry out the appropriate treatment.