Calf: The belly or fleshy hind part of the back of the leg below the knee. The calf is made up mainly of the gastrocnemius muscle. Pain in the calf is commonly caused by muscle strain, but can be caused by blood clots in veins of the legs. QUESTION What causes tooth decay? See Answer From Healthy Resources 10 Rheumatoid Arthritis SymptomsWhat Is Exocrine Pancreatic Insufficiency?Truth About Vitamin B12 Featured Centers Good and Bad Foods for PsoriasisVideo: Getting Personal on Life With MS Health Solutions From Our Sponsors Shot-Free MS Treatment Your Child and COVID-19