Adhesive capsulitis (AC) is a debilitating condition that causes global restriction and pain at the glenohumeral joint. Physiotherapy treatment is often first line treatment management. Patients with failed conservative management are commonly referred to a specialist consultant for further treatment. Over the last 20 years, extracorporeal shock wave therapy (ESWT) has gained popularity as a treatment for various orthopaedic presentations, including chronic soft tissue conditions, being non-invasive, resulting in good outcomes with minimal side effects. There is a lack of evidence on the clinical effectiveness of ESWT for chronic AC following failed conservative treatments, with the available literature reporting positive outcomes, however, with heterogeneity in treatment protocols. This proposed study aims to explore the feasibility of a full trial of ESWT as a treatment for AC using a standardised treatment protocol, and clinical effects on outcomes of pain, function and shoulder joint range of movement in persons with chronic adhesive capsulitis.

A Delphi study will first explore expert opinion for the optimum treatment protocol of ESWT as a treatment for chronic AC, followed by a mixed methods explanatory sequential study that includes a pilot trial with nested qualitative interviews. The Shoulder Pain and Disability Index, numerical pain rating scale, EuroQol-5D, and digital goniometer will be used to measure self-reported pain and function, pain, health-related quality of life, and shoulder joint range of movement, respectively. Quantitative data will be analysed by descriptive statistics. Qualitative data will be collected through semi-structured interviews. Interview data will be analysed using Braun and Clarke's inductive thematic analysis approach. The study will be conducted in an out-patient clinical setting in a community health hub facility, with patients recruited from an NHS Orthopaedics waitlist. Data collection is planned over a nine month period. This study is not affiliated with funding streams.

Shoulder AC, commonly known as frozen shoulder, is a self-limiting condition that affects three to five percent of the population and up to 20 to 30 percent in persons with diabetes mellitus. Its aetiology is still being understood with evidence supporting a chronic state of low-grade inflammation and elevation of pro-inflammatory lipoproteins resulting in fibrotic changes in the glenohumeral capsule. This results in pain, reduced shoulder range of movement (ROM) and functional disability that can spontaneously resolve between one to three years, with 40 percent reporting persistent symptoms at long-term follow up (mean follow up time 4.4 years, range 2 - 20 years). AC can occur spontaneously, as a primary insidious onset, or secondary, following a post-traumatic event such as shoulder surgery or rotator cuff injury. Treatment for AC commonly consists of conservative management interventions including pharmacotherapy, physiotherapy, and corticosteroid injection, with referral to secondary care if symptoms persist for interventions such as manipulation under anaesthesia and arthroscopic capsular release.

The treatment interventions or surgical procedures for AC may not always be effective or suitable for all patients due to conditions that may increase risk of complications such as respiratory conditions, allergies, previous surgery complications, co-morbidities (e.g., liver, cardiovascular and kidney disease), and patient choice. Untreated conditions and long-wait times can lead to chronicity further impacting an individual's health and increasing costs to the National Health Service (NHS). Musculoskeletal (MSK) conditions are estimated to cost to the British government an estimated £7 billion per year, accounting for one third of the NHS budget. In a United Kingdom (UK) health survey evaluating the prevalence of chronic pain (duration of pain 12 weeks or more), labelled MSK conditions as a long-lasting illness, accounting for 81 percent of participants, and of this, 24 percent involving the shoulder. Chronic MSK pain has also been linked to 17.5 percent of work absences, anxiety, depression, and health inequalities.

Over the last 20 years, EWST, has gained popularity as a treatment modality for orthopaedics conditions such as chronic tendinopathies. EWST can be generated as focused high- energy (>0.60 millijoules (mj)/mm2) shock waves or emitted as radial low (<0.08 mJ/mm2) to medium-energy (<0.28 mJ/mm2) shock waves. ESWT stimulates soft tissue healing via a biological response of mechanotransduction through neovascularisation, reduction of tendon matrix inflammatory markers such as metalloproteinases and interleukins, assists with the migration and differentiation of mesenchymal stem cells, and enhances the natural healing microenvironment. To date, therapeutic EWST has been shown to be clinically effective to treat bone non-unions, chronic soft tissue disorders such as tendinopathies and recalcitrant MSK conditions commonly involving the supraspinatus muscle tendon, patellar tendon, Achilles tendon and plantar fascia, and has become a favourable alternative treatment for individuals who have exhausted conventional conservative interventions.

A review of the literature exploring the use of ESWT as a treatment for chronic AC found seven randomised control trials (RCT) reporting significant improvements in function, pain and shoulder ROM in groups that received ESWT. The literature found improvements in all outcomes within 12 weeks when compared to a control group.

Although the literature demonstrates positive outcomes, due to the small number of studies, small sample sizes, and heterogeneity of treatment protocols, there is insufficient evidence for it to be a recommended treatment for AC by national health guidelines (e.g., National Institute for Health and Care Excellence). Further research is therefore required to determine the acceptability and viability of this intervention in the UK healthcare framework, with potential to conduct a full-scale RCT.

Inclusion Criteria:

1. Participants aged 18 years and older.
2. Diagnosis of primary or secondary shoulder AC of a greater than three-month duration.
3. Diagnosis of AC by an orthopaedic consultant or upper limb Advanced Practice Physiotherapist.
4. Participants can attend an outpatient rural physiotherapy department to receive shockwave therapy intervention.
5. They understand English.

Exclusion Criteria:

1. Participants who have bilateral shoulder pain, capsular tightness, calcific rotator cuff tendinitis, rotator cuff tear (atraumatic or traumatic), previous surgery on the affected shoulder, shoulder fracture, dislocation or subluxation, glenohumeral or acromioclavicular arthritis, malignancy, inflammatory disorders, neuromuscular disorders, presence of severe osteoporosis, pulmonary diseases, implanted pacemaker and pregnancy.
2. They have conditions related to ESWT contraindications (e.g., pregnancy, pacemaker, metal work or joint replacement near the treatment site, blood clotting disorder, use of anti-coagulants, less than six weeks of receiving a steroid injection over treatment site, malignancy, local infection or open wounds, skeletal growth places, under 18 years old).
3. Symptom duration less than 12 weeks.
4. Absent or altered skin sensation.
5. They are unable to give full informed consent.