Spasticity, possibly more commonly known as muscle spasms, is a disruption in patterns of muscles vigorously contracting. Typically, muscles follow a complex series of movements which sees some muscles tightening while others relax during normal actions. However, nerve damage in the central nervous system disrupts this pattern and the end result is several muscles involuntarily contracting all at once. The condition is predominantly seen in the legs, but is also known to occur in the arms.