Background: The early management of orthopaedic outpatients by physiotherapists may be useful in reducing public hospital waiting lists. Physiotherapists in Australia are prevented by legislation and funding models from investigating, prescribing, injecting and referring autonomously. This gap in service is particularly noticeable in the management of shoulder pain in early-access physiotherapy services, as patients needing corticosteroid injection face delays or transfer to other services for this procedure. This trial will investigate the clinical (decision making and outcomes) and economic feasibility of a physiotherapist prescribing and delivering corticosteroid and local anaesthetic injections for shoulder pain in an Australian public hospital setting. Methods/Design: A double-blinded (patient and assessor) non-inferiority randomised controlled trial will compare an orthopaedic surgeon and a physiotherapist prescribing and delivering corticosteroid injections to the shoulder. Agreement in decision making between the two clinicians will be investigated, and economic information will be obtained for estimating disease burden and an economic evaluation. The surgeon and the physiotherapist will independently assess patients, and 64 eligible participants will be randomised to receive subacromial injection of corticosteroid and local anaesthetic from either the surgeon or the physiotherapist. Post-injection, all participants will receive physiotherapy. The primary outcome measure will be the Shoulder Pain and Disability Index measured at baseline, and at 6 and 12 weeks post-injection. Analysis will be conducted on an intention-to-treat basis and compared to a per-protocol analysis. A cost-utility analysis will be undertaken from the perspective of the health funder. Discussion: Findings will assist policy makers and services in improving access for orthopaedic patients.