Rotator cuff tears are a common injury that lead to pain and loss of function for those who suffer from it. Treatment includes the use of arthroscopic surgery to return function to the patient and reduce their pain. This study is interested in a technique that has the potential to improve patient outcomes in terms of less pain and better function after their surgery. Autologous Conditioned Plasma (ACP) or Platelet Rich Plasma (PRP) is the intervention of interest, which is simply the patient's own blood that is withdrawn and spun down to obtain a high concentration of cells called platelets. Platelets release growth factors important for healing, as well as fibrin, which acts like a biological glue. The PRP is then re-injected into the shoulder at the time of surgery and again at 4 weeks. It has been shown to accelerate healing in other studies for injuries such as chronic elbow tendinopathy, but there is no randomized controlled trial that evaluates the effect of PRP in rotator cuff tears. It is on this basis that the study is being performed. Participating patients will receive either a PRP injection or a placebo (normal saline) and the effects will be compared at 2 weeks, 4 weeks, and 6 weeks based on a pain score and return to function questionnaires. The primary hypothesis for this study is that ACP compared with placebo is effective in reducing pain at the site of a rotator cuff injury that has undergone arthroscopic repair. It is expected that ACP administered during surgery and 4 weeks post-surgery will reduce 6-week pain scores compared to the placebo group.

Inclusion Criteria:

• Men or women who are between 18 and 70 years of age.
• Primary, traumatic or degenerative rotator cuff tears measuring 3 cm or less.
• Rotator cuff tears requiring arthroscopic repair within 18 months of initial diagnosis.
• Provision of informed consent.

Exclusion Criteria:

• Rotator cuff tears secondary to a fracture.
• Patients with an associated dislocation at the time of randomization.
• Rotator cuff tears that underwent prior surgical repair or revision arthroscopy.
• Non-surgical rotator cuff associated treatment in the 1 month prior to randomization including corticosteroid injection and anti-inflammatory treatment.
• Prior platelet rich plasma injection.
• Pre-existing conditions associated with upper extremity pain, including arthritis, ongoing infection, carpal tunnel syndrome, cervical neuropathy or other nerve pathology, local malignancy, and systemic disorders (e.g., uncontrolled diabetes, hypothyroidism).
• Patients with gross shoulder instability.
• Patients with an active infection.
• Patients who are pregnant or plan to become pregnant in the next 12 months.
• Patients with a pre-operative platelet count less than 125,000 and a pre-operative hemoglobin of 7.5g/dl or less.
• Likely problems with follow-up (i.e. patients with no fixed address, report a plan to move out of town, or intellectually challenged patients without adequate family support).
• Patients who do not read and speak English.
• Patients participating in another ongoing trial that would interfere with the assessment of the primary or secondary outcomes.
• Any other reason (in the judgment of the surgeon).