Rigidity

Key Facts

  • Rigidity is present in about 90-99% of PD cases.
  • Rigidity is independent of the velocity used to manipulate the limb which distinguishes it from spasticity.
  • Muscular rigidity can be seen unilateral or bilateral.
  • The “cogwheel” phenomenon is a particular type of rigidity occurring in PD. It is thought to be tremor superimposed on rigidity.
  • Rigidity of the trunk may be present.
  • Some patients refer to rigidity as “tightness” in their limbs.

Rigidity can be defined as increased resistance when stretching a muscle passively and is commonly associated with bradykinesias. Rigidity is one of the symptoms that has important implications in the quality of life of all patients; therefore, its assessment and treatment is important in every single case.

Rigidity, while seldom the main symptom early in PD, is experienced as stiffness of the arms or legs beyond what would result from normal aging or arthritic changes. Like other motor symptoms, rigidity often presents unilaterally and continues to manifest asymetrically, contributing to the postural deformities that are seen in many PD patients. Treatment with levodopa and dopamine agonists works well with rigidity.

References: 

Ebadi M, Pfeiffer, R; Parkinsons's Disease; CRC Press; 2005; P:173-174