The most common causes of swelling in the left foot are varicose veins of the lower limbs, gouty arthritis, venous thrombosis of the lower limbs, and external injuries, as follows: 1. varicose veins of the lower limbs: this can lead to significant swelling in the left foot, which can be improved by reducing standing time, wearing elastic stockings, and actively elevating the affected limbs in the early stages. 2. gouty arthritis: localized gouty arthritis can lead to significant swelling in the left foot. 3, lower extremity venous thrombosis: This can lead to significant swelling of the left foot, which can be clearly diagnosed by vascular ultrasound examination of the left lower extremity. 4, external force injury: When the left foot is subjected to external force, causing local soft tissue injury, fracture or dislocation, it can also lead to significant swelling of the left foot. Obvious swelling symptoms.