BackgroundThere is no consensus about the optimal treatment strategy for frozen shoulders (FS). Conservative treatment consisting of intra-articular corticosteroid infiltrations and physiotherapy are considered appropriate for most patients. However, with a conservative strategy, patients experience a prolonged rehabilitation period with a considerable amount of pain and disabilities in daily life. Also, at long term, a residual amount of pain and restriction of range of motion is frequently reported. Manipulation under anesthesia is a short and relative simple procedure with the potential to rapidly reduce symptoms and restore the range of motion. The objective of this trial is to evaluate the effectiveness of MUA followed by a PT program compared to a PT program alone, in the treatment of patients with a stage two FS. We hypothesize that the course of the disease can be shortened with MUA with a quicker functional recovery.MethodsThis is a prospective, single center, randomized controlled trial. Eligible patients will be allocated to either the manipulation (MUA) group or the physiotherapy alone (PT) group. In the MUA group manipulation will be performed under interscalene block, directly followed by an intensive physiotherapy treatment protocol, with the goal to maintain the obtained range of motion. Patients allocated to the PT group are given advice and education and receive a written protocol to hand out to their physical therapist based on the recent guideline of the Dutch Shoulder Network for the treatment of frozen shoulders. Descriptive statistics will be used to describe the sample size, patients demographics, presence of diabetes mellitus, range of motion, duration of symptoms till randomization and will be presented for each treatment group. The SPADI is used as primary functional outcome parameter. Secondary outcome parameters are; OSS, NPRS, EQ-5D 3-L, passive range of motion, WORQ-UP, duration of symptoms, usage of analgesics and adverse events. A sample size of 41 subjects in each group was calculated. Follow up is planned after 1,3 and 12 months. The length of physiotherapy treatment in both groups is variable, depending on individual progression. Differences between groups in outcome parameters will be analysed using the linear mixed modelling and the restricted maximum likelihood ratio technique for estimating the model parameters.DiscussionSuccessful completion of this trial will provide evidence on the best treatment strategy for patients with a stage two frozen shoulder. The results of this study can lead to a better understanding for the role of manipulation in the treatment of frozen shoulders.Trial registrationThis trial is registered in the Dutch Trial Register under the number NTR6182 on the 20th of February 2017.