The common causes of unilateral ankle swelling are shown as follows: 1. Local gout attack: If patients with long-term hyperuricemia, there may be uric acid accumulation leading to uric acid arthritis, gouty arthritis, and single ankle edema or even redness; 2. Lower limb vascular lesion: Especially lower limb venous reflux disorder or venous valve insufficiency, leading to ankle swelling. It is recommended that patients go to the hospital for lower limb vascular ultrasound examination to clarify whether there are venous valve lesions in the arteries and veins of the lower limbs; 3, phlebitis: commonly known as phlebitis, patients can have local redness, swelling, heat and pain in the ankle. It is recommended that patients go to the hospital for routine blood examination to clarify whether there are elevated white blood cells and inflammatory cells, and if there are symptoms of systemic toxicity, anti-infection treatment is needed. 4, rheumatic immune diseases: such as Rheumatoid arthritis can involve the lower extremities and large joints; in addition, arthritis of the external dwelling of patients with spondyloarthritis often occurs in the ankle or foot. All these need to go to the rheumatology department for appropriate examination.