The causes of black joints are seen in the following areas: 1, poor blood circulation at the finger joints, the phenomenon of bruising, mostly related to external pressure. You can use massage or hot compresses to effectively relieve the symptoms, if not relieved to go to the hospital to avoid the phenomenon of arthritis. 2, it may be due to long-term maintenance of a posture for too long, or flexion of the joints for too long, generally due to poor blood circulation, pay attention to more sports activities. 3, the joint skin is obviously black and accompanied by a sense of pain. This is often caused by arthritis or rheumatoid arthritis, which may be accompanied by morning stiffness, redness, swelling, fever and other symptoms, and requires further examination to determine the cause. 4. Blackening may be hyperpigmentation. The joint parts are often worn and active, and the color will be darker compared to other parts. As long as there is no obvious itching, flaking and other symptoms, there is no need to worry too much.