The most common causes of spasticity are cerebral palsy, physical trauma (brain or spinal cord injury), stroke and multiple sclerosis (MS).

Spasticity may not be present all the time; it may be related to a trigger or stimulus such as pain, infection or even tight clothing. It may be painful, especially if it pulls joints into abnormal positions or prevents a normal movement of the joints. In some patients, spasticity may cause slight muscle stiffness; in others there is permanent shortening of the muscle. When the muscle is permanently shortened, the joint becomes misshapen. This is called a contracture and is one of the most significant consequences of spasticity. Another closely related problem with muscles in many people who have spasticity is clonus: rapid, repeated muscle spasms.

While spasticity may affect any muscle group, there are some common patterns. When spasticity affects one or both arms, flexed elbow, wrist, and clenched fist may result. These can all affect the person’s ability to care for themselves normally or cause difficulties with walking. Spasticity of the legs can cause flexed hip, adducted thigh, stiff or flexed knee, equinovarus foot, and hyperextended great toe.

Spasticity may be limited to one area (localized), several nearby areas (regional), or many muscles or muscle groups of the body (generalized). When spasticity is generalized daily care may be challenging and lack of comfort becomes an important consideration for treatment approaches.