The causes of unexplained ankle swelling and pain are chronic ankle ligament strain and degenerative osteoarthropathy, as follows: First, chronic ankle ligament strain: for example, frequent prolonged walking or strenuous sports often cause damage to the ligaments of the ankle joint, which can gradually lead to chronic strain of the ankle ligaments, manifesting as pain in the ankle after walking, accompanied by swelling of the joint. Secondly, degenerative osteoarthropathy: this condition is mostly found in middle-aged and elderly patients, mainly due to degeneration and loss of joints and cartilage, degenerative bone spurs around the joints, too much walking can easily cause stress concentration in the joints, so there will be painful movement of the ankle joint and swelling of the ankle joint.