DEFROST: A clinical trial testing metformin as a treatment for frozen shoulder or shoulder tendinopathy.

The Department of Orthopaedics and Traumatic Surgery at Royal North Shore Hospital is conducting research to test a new treatment for frozen shoulder and tendinopathy. The treatment being investigated is a drug called Metformin. Metformin is currently approved to treat Type 2 diabetes. It is not currently approved to treat frozen shoulder or tendinopathy. The aim of the study is to determine whether Metformin is effective in reducing pain and loss of movement, and speeding up recovery in patients suffering from a frozen shoulder or tendinopathy. Our investigations in the Department of Orthopaedics and Traumatic Surgery's laboratory at Royal North Shore Hospital have shown that this drug acts on the cause of the stiffness in these shoulder conditions and may be effective in reducing the pain and its duration. Results of research undertaken in our laboratory, also suggest that blood tests may help diagnose these conditions and indicate if a patient is recovering well. Current treatments for these conditions have limited success. It is therefore important that more research is done into new treatments, including drug treatments. Frozen shoulder and tendinopathy cause enormous pain, which can lead to loss of sleep, difficulty in dressing and toileting, and participating in occupational and recreational activities. This drug may enable patients to return to their usual activities more quickly. This research has been initiated by the study doctor, Professor Sonnabend, who is an orthopaedic surgeon at Royal North Shore Hospital. Patients are eligible for this study if they: * Are aged between 40 and 70; * Have shoulder pain in only one shoulder, which may or may not be following an injury; * Have pain at the ends of the range of movement of their shoulder in all directions; * Have a loss of movement in the shoulder; * Have had symptoms for less than 3 months; * Have an x-ray that is normal; * Are non-diabetic. Participants will be given either metformin or a placebo to take twice daily for 3 months. The one taken will be chosen randomly. Participants and the study doctor will not know which treatment a participant is receiving. Participation in the study will involve 4 medical appointments at Royal North Shore Hospital, which would be at least the usual number of visits that would be made to a specialist, but in addition to the consultations, questionnaires will be completed and blood samples will be taken. Participation in any research project is voluntary. This study will not cost participants anything.