Background Clinical key aspects of camptocormia in patients with idiopathic Parkinson's disease (PD) await further definition. Methods Based on a self‐assessment of PD patients, we performed an observational study, asking patients with subjectively felt involuntary forward bending to return a questionnaire and provide photographs showing their axial disorder. Forty‐two matched PD patients without subjective signs of camptocormia were recruited as controls. Results The stooped posture of patients with advanced PD without camptocormia is characterized by a forward bending angle of always less than 30 degrees. Of the 145 camptocormia patients in our study, 70% had an angle ≥30 degrees. The patients with a more‐severe forward bending angle were more severely affected in daily life than those with an angle of less than 30 degrees. Back pain was more frequent (81% vs. 43%) and more severe in PD patients with camptocormia than in controls. Back diseases in camptocormia PD patients were also significantly more frequent than in the PD control patients (55% vs. 26%). Camptocormia is a relevant burden in everyday life. Seventy‐seven percent of patients needed walking aids and 85% reported specific disabilities attributed to camptocormia (e.g. increased risk of falling, dyspnea, problems in eating or swallowing). Conclusions Camptocormia cannot be clinically defined based on the forward bending angle alone, but an angle larger than 30 degrees is only found in camptocormia. Back pain is an essential aspect of camptocormia in PD. Back diseases can be seen as a risk factor in these patients.

Camptocormia in Parkinson's disease (PD) is an axial postural disorder usually accompanied by histopathological changes in the paravertebral muscles of unknown etiology. The diagnostic potential of magnetic resonance imaging (MRI) of back muscles in camptocormia has not been systematically assessed. Our objective was to characterize pathological muscle changes with MRI and to develop radiological criteria for camptocormia. The criteria edema, swelling and fatty degeneration in 20 idiopathic PD patients with camptocormia were assessed using MRI (T1w and short tau inversion recovery (STIR) sequences) of the lumbar trunk muscles and compared with 20 group-matched PD patients without camptocormia. Edema and fatty degeneration of the paravertebral muscles were significantly more frequent in camptocormia. Edema correlated negatively and fatty degeneration positively with the duration of camptocormia and not PD. Swelling of the paravertebral muscles, edema and swelling of the quadratus lumborum muscle and rare edema of the psoas muscle were only found in camptocormia patients. In this case-control study the defined MRI criteria distinguish the group of PD patients with camptocormia versus those without. Our findings suggest dynamic changes in the MRI signals over time in the paravertebral muscles: edema and swelling are found initially, followed by fatty atrophic degeneration 2-3 years after the beginning of camptocormia. Muscle MRI qualifies as a tool for categorizing phases of camptocormia as acute or chronic, with potential consequences for therapeutic approaches. The involvement of muscles beyond an isolated impairment of the paravertebral muscles implies a more systemic view with a deregulation of lumbar trunk muscles.