Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor symptoms including muscle rigidity as one of major motor symptoms affecting quality of life of Parkinson's disease patients, thus we aim to assess and quantify muscle stiffness in those patients using Ultrasound shear wave elastography .

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor symptoms like tremors, bradykinesia, muscle rigidity, and postural instability, as well as various non-motor symptoms . While the exact cause of Parkinson's disease is not fully understood, it is thought to result from a combination of genetic and environmental factors, leading to the degeneration of dopamine-producing neurons in the brain . PD is the second most common neurodegenerative disorder after Alzheimer's disease, primarily affecting those over 60, with a higher prevalence in men . The disease significantly impacts quality of life due to progressive motor and non-motor disabilities, and while treatments can alleviate symptoms, there is currently no cure . Disease progression and prognosis vary, with advanced stages often leading to severe disability and reduced life expectancy .

Muscle rigidity, one of the major motor symptoms, refers to the increased resistance when muscles are passively stretched . Accurate assessment of muscle stiffness is essential for monitoring disease progression and evaluating therapeutic interventions .

Traditionally, clinical assessment tools like the Unified Parkinson's Disease Rating Scale (UPDRS), part III, are used to evaluate rigidity severity in PD patients . These assessments, involving manual joint movement and muscle palpation by professionals, are subjective and prone to error . Thus, there is a growing need for noninvasive, quantitative tools to assess muscle stiffness in PD patients .

Tools like electromyography (EMG) and myotonometry offer quantitative measurements . Ultrasound shear wave elastography (SWE) is another non-invasive technique that measures tissue stiffness by analyzing shear wave propagation. While SWE shows promise for various conditions, its application in PD-related muscle rigidity remains relatively unexplored .

Inclusion Criteria:

• patient diagnosed with Parkinson's disease
• Age between 40-85 years
• No other neurological or musculoskeletal disorders affecting the examined limb muscles.

Exclusion Criteria:

• History of other neurological or musculoskeletal disorders affecting the examined limb muscles.
• History of significant trauma or surgery in the examined limb within the last year.
• patients with contraindications to ultrasound( such as open skin wounds or severe skin conditions in the area of interest).

Any patients diagnosed with Parkinson's disease and meeting the eligibility criteria.