Left calf swelling and pain may be related to the following reasons: 1, it may be caused by trauma here, such as here there is a fracture or serious blunt contusion of soft tissue, will rapidly develop internal bleeding and sterile inflammation, will lead to the left side of the calf has a very obvious swelling and pain. 2, it may be caused by the left side of the calf of the infection, such as here there is an open injury, not properly dealt with, may be rapidly develop into cellulitis, which in turn leads to significant swelling and pain in the left calf.3. It may be caused by lesions on the surface of the skin, such as the patient’s presence of onychomycosis and severe athlete’s foot, and there is the possibility of severe dandruff, which is a lymphadenitis, at which time there is a symptom of redness, swelling, warmth, and pain in the entire left calf.4. It may be caused by overexertion, for example, the patient does something that involves The left side of the calf excessive activities, due to do a lot of anaerobic respiration produces a lot of lactic acid, and then stimulate the left calf muscle, it produces a feeling of swelling and pain.