Due to the lack of further studies on the influence of age factors on plantar fasciitis, this study evaluates the characteristic observation points of magnetic resonance imaging in various age cohorts of patients with plantar fasciitis to help diagnosis. A retrospective analysis of 160 cases of plantar fasciitis patients and normal subjects (who have the disease unrelated to plantar fasciitis) who have undergone an MRI examination in our institution. The two groups were separately divided into young adult subjects (36 to 44years old), middle age adult subjects (45 to 59years old), and older adult subjects (60 to 79years old). Data was gathered regarding plantar fascia thickness, the coronal length of the plantar fascia at the calcaneal origin, the signal intensity of plantar fascia and surrounding structures, and the presence or absence of plantar calcaneal spurs, all of which were assessed objectively by the investigators. There were statistical differences in the thickness of plantar fascia between two groups of three age cohorts (Older adult patients: 0.59 ± 0.09cm; Middle age adult patients: 0.49 ± 0.09cm; Young adult patients: 0.47 ± 0.05cm) (all p < 0.001). In addition, there were also statistical differences in the high signal intensity changes of the plantar fascia and surrounding soft tissues between two groups of three age cohorts (all p < 0.001). In older adult plantar fasciitis patients, with regard to plantar calcaneal spur discovery, there was a statistical difference between the two groups (Chi-square = 12.799. df = 1. p < 0.001). In plantar fasciitis cases where a diagnosis is difficult, abnormalities in the soft tissue surrounding the plantar fascia in patients of low age are noteworthy. In older adult patients, the discovery of plantar calcaneal spurs with abnormal thickening of plantar fascia deserves attention, and abnormal MRI findings are more manifest. But the final diagnosis should be based on the medical history. Level 3.