Parkinson's disease (PD) is a multisystem neurodegenerative disorder that is increasingly recognized in our ageing population. It is characterized by cardinal clinical features including bradykinesia, tremor, rigidity, and postural instability. For most people with PD, the most serious concern is with the motor system: stiffness, slowness of movement, impaired handwriting and coordination, poor mobility and balance. However, more than half of all people with PD have experienced painful symptoms. Most people experience aching, stiffness, numbness and tingling at some point in the course of the illness. Defazio et al reported that pain may begin at clinical onset of PD or thereafter as a non-motor feature of PD.5 Aching muscles and joints are especially common in PD. Rigidity, lack of spontaneous movement, abnormalities of posture and awkward mechanical stresses all contribute to musculoskeletal pain in PD.

One of the most common musculoskeletal complaints is shoulder pain or shoulder disorders, including frozen shoulder, bursitis, and rotator cuff lesions. Actually, shoulder pain or shoulder disorder can be the first sign of PD. The prevalence and severity of shoulder disorders in Parkinson's disease are not totally clear. In a retrospective study, Stamey found shoulder pain was present in 11% of patients with PD.

Over the past ten years ultrasound (US) has become popular in the evaluation of shoulder disorders. It allows for the detailed assessment of a wide range of changes involving different anatomic structures of the shoulder joint, including rotator cuffs, biceps tendon, and subdeltoid bursa. Koh et al found among 33 PD patients, 22 patients had abnormal US findings on the dominant side, and all 22 patients with abnormal US finding had a tendon tear and 9 patients had frozen shoulder. However, there were no control group in Koh' s study, and diagnosis of frozen shoulder with US findings is still controversial.

The purposes of this study are to evaluate patients with PD with a combination of physical examination and US study of the shoulder, and to compare the frequency and type of shoulder lesion in US between patients with PD and normal subjects. The investigators also plan to test the correlation between shoulder disorders or US abnormality and the severity of PD.

Inclusion Criteria:

• Patients fulfilled the diagnosis of PD, as described by the United Kingdom Parkinson's Disease Society Brain Bank,
• Aged 50 to 80 years old.

Exclusion Criteria:

• Fracture or dislocation of the shoulder,
• Previous shoulder joint surgery,
• Severe medical comorbidities,
• Cognitive impairment (Mini-Mental Status Examination < 24).

Patients with PD will be recruited consecutively from a neurology clinic. A group of sex- and age-matched normal subjects with be recruited from the public.