There are many different variations on the definition of spasticity that a physician will use. The common one is “a velocity-dependent increase in resistance of a muscle to stretch” meaning the faster you try to move a limb or joint the greater the spasticity that results.

Obvious severe spasticity is tight, stiff muscles involved in movement, especially of the arms and legs, making those movements difficult, uncoordinated or uncomfortable. However, spasticity can also affect other functions such as speech and swallowing.

Spasticity can also be extremely painful and can interfere with function and the patient's comfort. Spasticity can affect all aspects of daily living such as walking, dressing, sleeping, communication, feeding and personal hygiene, making these activities both time-consuming and difficult for both the patients and their caregivers. Uncontrolled, poorly managed spasticity is also recognised for the increased potential of causing additional medical problems such as pressure sores, joint stiffness and muscle contractures requiring additional surgical and medical interventions. Contractures are of particular concern that orthopaedic surgery may resolve but they often redevelop if the underlying spasticity is not managed properly.

Spasticity is also associated with decreased coordination, dexterity, planning of movements, muscle weakness and muscular endurance. It can vary according to the patient's state of alertness, activity or posture.

Spasticity can be aggravated by many factors such as pain, stress, emotional state, tiredness, extremes of temperature, illness, constipation and diarrhoea, tight clothing and orthoses such as splints, immobility and hormonal changes such as the menstrual cycle