Frozen shoulder, or adhesive capsulitis, has three stages: freezing, when the joint becomes increasingly painful and gradually stiffens up; frozen, when the pain lessens but movement is severely limited; and thawing, when movement gradually returns.
For most patients, the process takes an average of 18 months to two years, with the frozen phase lasting anywhere from four to 12 months.
About 70 per cent of patients are female. Women aged between 35 and 65 who also have conditions such as diabetes, hypothyroidism or ischaemic heart disease are most at risk of being affected.
Diabetes is a key risk factor that is driving a rise in the incidence of frozen shoulder. It can also double the length of time needed for the condition to resolve, and worsen the severity of the symptoms.
We hope that it will not only slash the length of time the condition lasts, but also reduce the severity of the symptoms, having a positive impact on a debilitating condition that predominantly affects women.
Macquarie University Hospital orthopaedic surgeon, Associate Professor Sumit Raniga says there is currently no effective treatment for this debilitating condition, leaving patients with no option but to wait for it to go away.
"This is a problem that has not had enough attention because it's seen as relatively 'benign', but it's actually incredibly painful, debilitating and disruptive to patients' lives," Associate Professor Raniga says.
"Most people come to see me because the pain is so bad that it's preventing them from sleeping, and they are struggling even with simple activities of daily living like showering, tying their hair, dressing and driving.
"It's important to understand that frozen shoulder is not caused by damage to the joint, muscles or tendons as such, but you still get a severely stiff and painful shoulder.
"It's a molecular pathology with a biomechanical manifestation, but most orthopaedic surgeons don't have a background in molecular medicine, hence it is a mystery that remains unsolved.
"If you were to look into a frozen shoulder arthroscopically, the shoulder joint capsule is severely inflamed with a dense network of new blood vessels, almost like you could have landed on Mars."
What causes the freeze?
During the freezing phase, Professor Raniga says a network of new blood vessels forms in and around the shoulder joint capsule, which is a process known as neoangiogensis.
Hope: Associate Professor Sumit Raniga is conducting research using a molecular treatment to block the chemicals that trigger frozen shoulder pain.
The new blood vessels are surrounded by nerve endings that are full of 'Substance P', a neurotransmitter chemical associated with pain and inflammation.
Every time the person moves their shoulder during the freezing phase, Substance P is released from the nerve endings, causing pain.
With time, neoangiogensis provides the infrastructure for a variety of molecular factors that cause significant scarring of the shoulder capsule. This dense web of scar tissue then causes stiffness and restriction of movement during the frozen and thawing phases.
The role of surgical intervention and its timing is controversial, though a corticosteroid injection during the freezing phase may reduce the inflammation in some cases.
Physiotherapy is not effective during the freezing or frozen phases, but it becomes very important during the final thawing phase.
Tackling the problem at its source
For the past six years, Associate Professor Raniga has been researching the potential for a molecular treatment that could block the release of chemicals that trigger neoangiogensis in order to stop the process early in the freezing phase.
By minimising the production of new abnormal blood vessels, there is less concentration of the nerves full of Substance P, and potentially less of the molecular factors that cause scarring.
Molecular treatments are next-generation medicines also known as targeted therapies, and they are personalised to individual patients. They are already being used to treat cancers and neurodegenerative diseases, and researchers are investigating further potential applications.
"We have just begun a trial of a molecular treatment already used successfully for other conditions to test its effectiveness in frozen shoulder," Associate Professor Raniga says.
"We hope it will stop the development of new blood vessels and nerve endings around the shoulder capsule, removing the source of the pain, and preventing the scarring and stiffness.
"We hope that it will not only slash the length of time the condition lasts, but also reduce the severity of the symptoms, having a positive impact on a debilitating condition that predominantly affects women."
It is envisioned that the final version of the treatment could be a single injection.
If it proves safe and effective, the therapy will progress to a randomised control trial to test the difference in effectiveness between it and the most effective option currently available: an injection of corticosteroid and local anaesthetic.
But until a proven treatment for frozen shoulder becomes available, Associate Professor Raniga says prevention is the best option.
"Currently, the only way we have of reducing the chance of developing this condition is to ensure other contributing conditions such as diabetes are well controlled," he says.
"But there is still so much about it that we don't fully understand, like the potential role of hormones and the basis of genetic predisposition.
"This isn't 'benign' when you are the person living with it. It needs more research."
Associate Professor Raniga and his team are currently enrolling patients who have recently entered the freezing phase into the trial, and hope to have results to publish late next year.
For more information on this research contact [email protected]
Associate Professor Sumit Raniga is an Orthopaedic Shoulder and Elbow Surgeon and an Associate Professor in Orthopaedic Surgery. He is the Head of Upper Limb Surgery and Therapy at Macquarie University Hospital and director of the MQ Health Translational Orthopaedic Research Lab. He established the MQ Health Shoulder and Elbow Clinic.
