Plantar fasciitis (PF) is a prevalent, degenerative condition of the plantar fascia at its origin on the medial calcaneal tubercle, accounting for 11-15% of all foot symptoms requiring professional care. The diagnosis is primarily clinical, characterized by sharp "first-step" morning heel pain. However, imaging plays an essential role in atypical cases, preoperative planning, or when patients are unresponsive to conservative management. Ultrasonography (USG) is an accessible, dynamic, and cost-effective tool that typically demonstrates a thickened, hypoechoic fascia in PF. Magnetic Resonance Imaging (MRI) serves as the definitive gold standard, providing excellent soft-tissue contrast to identify perifascial edema, bone marrow edema, and microtears. This study aims to objectively correlate the measurement of plantar fascia thickness obtained via USG with that obtained via MRI, and to determine the statistical significance of this correlation to validate USG as a reliable primary imaging tool

Study Design and Population A prospective, cross-sectional study was conducted in the Department of Radiodiagnosis, IMS and SUM Hospital, Bhubaneswar. Fifty patients (representing 60 symptomatic heels) with a clinical diagnosis of plantar fasciitis were enrolled after obtaining informed consent and institutional ethical clearance. Imaging Protocol • Ultrasonography (USG): Performed using a high-frequency linear transducer (10–15 MHz). The patient was placed in a prone position. The fascia thickness was measured longitudinally at its thickest portion near the medial calcaneal insertion. • Magnetic Resonance Imaging (MRI): Performed on a 1.5 Tesla MRI scanner. Sagittal T1-weighted, T2-weighted, and STIR sequences were obtained. Fascial thickness was measured on the sagittal STIR images at the point of maximal thickness. Statistical Analysis Data were analyzed using SPSS software (Version 25.0). Continuous variables were expressed as mean ± standard deviation (SD). Pearson’s correlation coefficient (r) was utilized to determine the linear relationship between USG and MRI thickness measurements. To establish statistical significance, a p-value of <0.05 with a 95% Confidence Interval (CI) was considered the threshold.

The study evaluated 50 patients, out of which 10 had bilateral symptoms, resulting in 60 symptomatic heels analyzed. Table 1: Demographic Distribution of the Study Population Demographic Variable Value (n=50) Percentage (%) Age (Years) 45.2 ± 10.4 (Range: 28-65) - Gender Male 18 36% Female 32 64% BMI Classification Normal (<25.0) 12 24% Overweight (25.0-29.9) 26 52% Obese (≥30.0) 12 24% Laterality Unilateral 40 80% Bilateral 10 20% Description: Table 1 illustrates the baseline demographic characteristics of the 50 patients enrolled in the study. The population showed a female predominance (64%) and a clear trend toward higher Body Mass Index (BMI), with 76% of patients classified as either overweight or obese. Unilateral heel pain was far more common (80%) than bilateral presentation. Clinical Presentation Table 2: Clinical Characteristics and Symptom Profile Clinical Parameter Frequency / Mean Percentage (%) Mean Duration of Symptoms (Months) 6.5 ± 3.2 - Morning Heel Pain ("First Step" Pain) 48 96% Pain Worsening after Prolonged Standing 42 84% Point Tenderness over Medial Tubercle 50 100% Visual Analog Scale (VAS) Score (0-10) 7.2 ± 1.5 - Description: Table 2 details the clinical symptomatology reported by the patients. Almost all patients (96%) experienced the hallmark "first-step" morning pain, and 100% exhibited point tenderness over the medial calcaneal tubercle. The average severity of pain on the Visual Analog Scale (VAS) was moderately severe at 7.2. Imaging Findings Table 3: Ultrasonography (USG) Findings (n=60 heels) USG Finding Value / Frequency Percentage (%) Mean Fascia Thickness (mm) 5.42 ± 1.18 - Fascia Thickness > 4.0 mm 56 93.3% Hypoechogenicity 52 86.6% Loss of Fibrillar Architecture 48 80.0% Calcaneal Spur 34 56.6% Increased Vascularity (Doppler) 18 30.0% Description: Table 3 summarizes the primary and secondary findings identified on high-resolution USG. The normal threshold for fascia thickness is generally ≤ 4.0 mm; however, 93.3% of the symptomatic heels in this study exceeded this threshold, with a mean thickness of 5.42 mm. Associated inflammatory signs like hypoechogenicity and loss of fibrillar architecture were highly prevalent. Table 4: Magnetic Resonance Imaging (MRI) Findings (n=60 heels) MRI Finding Value / Frequency Percentage (%) Mean Fascia Thickness (mm) 5.56 ± 1.25 - Fascia Thickness > 4.0 mm 58 96.6% Intrasubstance High Signal (T2/STIR) 54 90.0% Perifascial Soft Tissue Edema 42 70.0% Calcaneal Bone Marrow Edema 28 46.6% Fascial Tear (Partial) 4 6.6% Description: Table 4 highlights the morphological alterations detected via the gold-standard MRI. MRI recorded a slightly higher mean thickness of 5.56 mm. It also demonstrated high sensitivity for deeper tissue changes, capturing intrasubstance high signal in 90% of cases and identifying calcaneal bone marrow edema in nearly half the cohort. Statistical Correlation Table 5: Statistical Significance and Correlation of Fascia Thickness (USG vs. MRI) Imaging Modality Mean Thickness (mm) Standard Deviation Pearson's r p-value Statistical Significance Ultrasonography (USG) 5.42 1.18 {0.892} <0.001 {Highly Significant} Magnetic Resonance (MRI) 5.56 1.25 Description: Table 5 is the core analytical table of the study. It compares the mean fascia thickness measurements obtained from both modalities. A Pearson correlation test was applied to determine the strength of the relationship. The result (r = 0.892) indicates a very strong positive correlation. Crucially, the p-value of <0.001 firmly establishes that this alignment did not occur by chance, proving high statistical significance.

Plantar fasciitis is a biomechanical over-usage condition predominantly affecting overweight individuals. In our study, 76% of the patients were classified as overweight or obese (Table 1), which aligns with established mechanical risk factors. A normal plantar fascia is uniformly echogenic and typically measures ≤ 4.0 mm in thickness. In our cohort, 93.3% of symptomatic heels exhibited a USG-measured thickness of >4.0 mm (mean 5.42 mm), generally accompanied by prominent hypoechogenicity and loss of standard fibrillar pattern (Table 3). MRI confirmed these morphologic changes, revealing a mean thickness of 5.56 mm alongside intrasubstance signal alterations (90%) and perifascial edema (70%) (Table 4). The cornerstone of this study is the statistical evaluation of the diagnostic agreement between the two modalities (Table 5). We observed a very strong positive correlation (Pearson's r = 0.892) between the thicknesses measured by USG and MRI. More importantly, this relationship demonstrated robust statistical significance (p < 0.001). This statistically validates that high-resolution USG is exceptionally accurate for the morphological quantification of the plantar fascia when compared to the MRI gold standard. While MRI remains superior for detecting secondary changes like bone marrow edema (identified in 46.6% of our cases) and subtle soft-tissue alterations, USG is fully adequate and highly reliable for the primary structural assessment of the fascia.

There is a highly statistically significant, positive correlation (p < 0.001) between high-resolution Ultrasonography and Magnetic Resonance Imaging in measuring plantar fascia thickness in patients with plantar fasciitis. Given its accessibility, cost-effectiveness, lack of ionizing radiation, and comparable diagnostic accuracy for fascial thickening, USG should be heavily utilized as the primary frontline imaging modality. MRI should be reserved for recalcitrant cases or when complex associated pathologies, such as occult fractures or fascial ruptures, are clinically suspected.

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