T1-weighted signal intensity changes in the plantar fascia, soft-tissue edema superficial to the plantar fascia and calcaneal spurs are common findings in asymptomatic patients and should be used with caution when diagnosing plantar fasciitis, according to a study published online May 7 by Radiology.

Although the diagnosis of plantar fasciitis is typically suspected at clinical examination, additional diagnostic investigation is necessary in patients who don’t respond to therapy or those with chronic pain. MRI and ultrasonography are utilized to depict alterations of the plantar fascia, and in the clinical routine at the Orthopedic University Hospital Balgrist in Zürich, Switzerland, lead author Christine Ehrmann, MD, and colleagues commonly observed slight signal intensity changes adjacent to the plantar fascia in patients with foot disorders other than plantar fasciitis. Because these findings contradict those of previous research, Ehrmann and colleagues sought to determine the spectrum of MRI findings at the calcaneal attachment of the plantar fascia in asymptomatic volunteers.

During the study, MRI was performed in 77 asymptomatic volunteers between the ages of 23 and 83 with a 1.5-T system. Two radiologists independently assessed signal intensity characteristics and the thickness of the medial, central and lateral fascicles of the plantar fascia. They also noted the presence of soft-tissue edema, bone marrow edema and bone spur formation at the attachment of the plantar fascia.

After analyzing the collected datasets with inferential statistic procedures, the researchers found that the mean thickness of the plantar fascia was 0.6 millimeters for the medial fascicle, 4 millimeters for the central fascicle and 2.3 millimeters for the lateral fascicle. An increase in signal intensity in the plantar fascia was observed with the T1-weighted sequence in 16 of the 77 volunteers, or 21 percent. Increased signal intensity was also seen with the T2-weighted sequence in six of the volunteers, or 7.8 percent, and with the short inversion time inversion-recovery sequence in another six volunteers.

Soft-tissue edema was observed deep to the plantar fascia in five study subjects and superficial to the plantar fascia in 16 of the patient group. A calcaneal spur was detected in 15 subjects and calcaneal bone marrow edema was present in four volunteers.

Results indicated that increased signal intensity within the plantar fascia with fluid-sensitive sequences is uncommon in asymptomatic patients.

“The knowledge of common, potentially physiologic, signal intensity changes on MR images of the plantar fascia in asymptomatic volunteers might help avoid overcalling plantar fasciitis in clinical routine,” wrote Ehrmann and colleagues.