Growing-Like Pains: 4 Types in Adult Legs Injuries Osteoarthritis Rheumatoid arthritis 1 2 3 4 Workout www.elyxrlabs.com One of the most common reasons for growing adult leg pain happens to be injuries Besides injuries, osteoarthritis is another common reason among adults, especially the senior population's pain in the legs Another kind of arthritis that causes growing pain in adults' legs is rheumatoid arthritis Working out causes tension in the muscles that might again become the cause of growing pains