We have developed an exercise protocol that we plan to evaluate in a future randomized controlled trial in combination with a corticosteroid injection. In accordance with the MRC Framework of Complex Interventions, which reccomends stepwise development of interventions and testing of feasibility before applying them to a trial, we aim to evaluate the feasibility of our intervention before initiating further trials.

The purpose of this non-randomized feasibility study is to test the feasibility and acceptability of this exercise protocol with addition of a corticosteroid injection with no aim of evaluating effects.

All participants in this study will receive the following interventions:

• An ultrasound-guided corticosteroid injection superficial to the insertion of the gluteus medius and minimus tendons on the greater trochanter of the hip.
• A home exercise program including 3 exercises, scalable to 3 different difficulty levels.
• A patient information leaflet containing relevant information on managing lateral hip pain.

The study design is a mixed methods feasibility study. We will include patients with GTPS that will receive a combined treatment of one ultrasound-guided corticosteroid injection in the lateral hip and a home exercise program, which is to be performed for a period of eight weeks.

For this study we plan to include 20 voluntary patients with GTPS from general practice and a private rheumatology practice. Participants will be recruited from general practice clinics and one private rheumatology practice in the North Denmark Region. Participants will attend physical visits at baseline and at 8-weeks follow-up. There is a booster session four weeks from baseline, that is conducted by phone. The content of each endpoint is stated in the following:

Baseline: Physical visit The baseline visit is managed by the project manager and includes a clinical examination and data collection of baseline characteristics. The participant will complete questionnaires. The patient information leaflet and the exercise instructions with a training diary will be handed out to the participant. The participant will receive an ultrasound-guided corticosteroid injection in the lateral hip. Appointments will be made for phone contact and 8-weeks follow-up.

Phone contact at one week from baseline: The project manager will contact the patients by phone after one week to clarify any questions about training instructions, the training diary or technical issues with accessing the video instructions. No data will be obtained.

4-weeks follow-up: Booster session and phone interview This booster session is conducted by the project manager via phone to encourage the participants to maintain their training routine, and to address any challenges, questions or difficulties in performing the exercises. In addition, we will do a short five-question interview to get feedback on the exercise intervention. The interview will be recorded, and the recordings will be transcribed. In addition to the phone conversation, the participants will receive questionnaires via email that are to be completed online in REDCap.

8-weeks follow-up: Physical visit at ReumaNord or Center for General Practice The participants will meet with the project manager at this final endpoint to hand in the training diary and complete questionnaires and repeat the interview done at the previous follow-up. The location will depend on what is logistically possible, but the appointment will in either case be made with the participant at baseline.

Inclusion Criteria:

• 35 years of age
• Self-reported pain on the outside of the hip for at least 12 weeks with an average intensity of present pain over the last week of at least 4/10 on a numeric rating scale 0-10 (0 being no hip pain and 10 being worst hip pain imaginable)
• Access to a computer, smartphone or tablet with internet connection
• Tenderness on palpation of the greater trochanter
• Reproduction of lateral hip pain with 30 sec single leg stance test
• Ability to speak and understand Danish (written and oral)
• In case of bilateral hip pain, the study hip will be the most painful at inclusion

Exclusion Criteria:

• Corticosteroid injection in the affected hip or other new treatment by a health professional within the last 3 months
• History of systemic inflammatory diseases, e.g. rheumatoid arthritis, spondyloarthritis
• Weekly intake of oral glucocorticoids
• History of other hip conditions, e.g. clinically significant hip osteoarthritis, hip dysplasia, prior hip surgery
• History of prior lumbar back surgery
• Current low back pain or episodes of low back pain within the last 3 months that have caused sick leave and/or treatment by a health professional
• Physical or mental disabilities that make it impossible to understand and/or perform exercises and complete questionnaires
• Current or planned pregnancy or breastfeeding