Tendonitis, cartilage injury and carpal bone fracture are some of the causes of tendon pain on the inside of the left wrist. 1. Tendovaginitis: If the wrist frequently carries out a certain repetitive activity, the tendon in the tendon sheath frequently rubs and develops aseptic inflammation, resulting in tendon pain. 2. Cartilage injury: When the cartilage of the wrist is chronically strained or traumatized, it will cause cartilage damage, which will also cause tenderness of the inner wrist. 3. Fracture of the carpal bone: After the wrist is injured, if there is a fracture of the carpal bone, it will cause medial tendon pain of the wrist, and it will also have an effect on the movement of the wrist. It can be seen that the causes of medial wrist tendon pain are very many, the specific cause of the disease need to consult a doctor in a timely manner, by the physician based on medical history, symptoms and related examinations.