The purpose of this study is to determine whether or not the use of an equimolar mixture of oxygen and nitrous oxide during the physical therapy for patients suffering from frozen shoulder (adhesive shoulder capsulitis) results in a gain in shoulder amplitude (Constant Score) and less pain as compared to patients undergoing physical therapy without this treatment.

Inclusion Criteria:

• Affiliated with a social security system
• Has signed the consent form
• Patient has a painful, or initially painful but stable frozen shoulder (adhesive capsulitis): stiffening characterized by a passive loss of amplitude on three planes. This loss of amplitude is greater than or equal to 50% of controlateral amplitude when the controlateral shoulder is considered as normal. Otherwise, the loss of amplitude is greater than or equal to 50% of normal anatomical values.
• Radiography confirms the integrity of the glenohumeral interspace.

Exclusion Criteria:

• Intercurrent, evolving or unstable pathology: cancer, advanced cardio-vascular pathology, severe infection
• The patient is taking a treatment that may interfere with the study (eg corticoids, pain killers, chemotherapy)
• Contra-indication for physical therapy
• Coagulopathy
• Advanced diabetes mellitus, with neurological or joint complications
• Contra indication for the experimental treatment
• Pregnant or nursing women
• Patient's mental state prevents him/her from understanding the nature of the study, its objectives and potential consequences.
• Patient under guardianship
• Patient is in an exclusion period determined by a previous study
• Patient not able to follow protocol constraints or timetable
• Medical history of local infection, polyarthritis or neuropathy that might explain the shoulder pain.
• Absence of radiculopathy of cervical origin, of rotator cuff tears or evolving shoulder tendinopathy, of severe omarthrose