The investigators aim to investigate whether combination of PRP injection with physiotherapy program could produce superior effect than either treatment alone.

Rotator cuff (RC) tears are a common source of shoulder pain and account for more than 4.5 million physician visits per year. In the overall population, the prevalence of RC tear is 20.7% and rises to 50% among patients older than 80 years. Partial-thickness and full-thickness RC tears has also been reported in 30% to 50% of the population aged older than 50 years. RC tears cause shoulder dysfunction, interfere daily activity, and may reduce quality of life. Treatment of RC tear includes surgical and conservative treatment. Considering operative risk, high possibility of re-tear after operation, and possible tendon healing with non-surgical treatment, for patients with a partial-thickness tear or a small full-thickness tear, conservative treatment is usually tried first. Previous report found that conservative treatment might be effective in 73% to 80% of cases with full-thickness tear of the rotator cuff. Conservative treatment of RC tear consists of rest, physiotherapy (including therapeutic exercise), non-steroidal anti-inflammatory drugs, and corticosteroid or hyaluronate subacromial injections. A. In addition, exercise has also been proven effective in the management of RC tear. In spite of the advanced surgical techniques and conservative methods, healing of RC tear remains problematic due to poor vascularization at the lesion site and failure to restore normal enthesis (tendon-bone junction) histology. Over past few years platelet-rich plasma (PRP) presents an attractive option to improve and accelerate healing of the rotator cuff lesion. PRP is defined as a portion of the plasma fraction of autologous blood having a platelet concentration above baseline (usually 2X to 4X). It is derived from centrifuging whole blood, and contains numerous growth factors, including platelet-derived growth factor, vascular endothelial growth factor, transforming growth factor, fibroblast growth factor, epidermal growth factor, hepatocyte growth factor, and insulin-like growth factor. Because of the increased concentration and release of growth factors, PRP can potentially enhance the recruitment and proliferation of tenocytes, stem cells, and endothelial cells. Given the autologous nature of PRP, safety concerns are minimal. Relative contraindications include patients with a history of thrombocytopenia, use of anticoagulants, tumor, metastatic disease, active infection, or pregnancy. Up to now no documented cases of carcinogenesis or tumor growth associated with the use of PRP has been reported. Previous studies showed using autologous leukocyte- and platelet-rich fibrin could increase vascularization during early healing of chronic rotator cuff tear, and that ultrasound-guided PRP injection is superior to dry needling in patients with supraspinatus tendon lesion. However, in a 1-yr randomized controlled trial with combination of 6 week physiotherapy program, PRP injection did not produce extra effect than placebo injection. Because controversy exists with regard to the effect of PRP injection, the investigators aim to investigate whether combination of PRP injection with physiotherapy program could produce superior effect than either treatment alone.

Inclusion Criteria:

1. Symptomatic rotator cuff tendinopathy, including small (<1cm) rotator cuff tear (partial or full-thickness), proven by ultrasound.
2. Duration of symptom longer than 1 month.
3. Aged ≥20 years old.

Exclusion Criteria:

1. Fracture, dislocation, or arthritis of the shoulder,
2. Previous shoulder joint surgery,
3. Rotator cuff tear with size ≥ 1cm,
4. Calcification of rotator cuff tendons,
5. Severe medical comorbidities, e.g., malignant neoplasms, blood dyscrasia, and serious infection, etc.,
6. Pregnancy,
7. Cognitive impairment (Mini-Mental Status Examination < 24),
8. Hypersensitive to thrombin.