Increased tone; Stiffness
Rigidity, also called increased muscle tone, means stiffness or inflexibility of the muscles. In rigidity, the muscle tone of an affected limb is always stiff and does not relax, sometimes resulting in a decreased range of motion. Rigidity is distinguished from spasticity, which is an increase in muscle tone present when the muscle is rapidly stretched. Rigidity with superimposed tremor is called cogwheel rigidity because of the ratchety quality of the limb tone when moved around a joint. Cogwheel rigidity is a characteristic motor feature of Parkinson’s disease. Increased rigidity may result in decreased arm swing when walking and frozen shoulder, which can also be manifestations of Parkinson’s disease.
References and Readings
- Fahn, S., & Jankovic, J. (Eds.). (2007). Parkinsonism: Clinical features and diagnosis. In Movement disorders (pp. 79–100). Philadelphia: Churchill Livingstone Elsevier.Google Scholar