Objective Plantar fascia (PF) is a thick connective tissue on the plantar surface of the foot that plays a crucial role in maintaining the longitudinal arch. Plantar fasciitis, characterized by inflammation of the medial tuberosity of the calcaneus, is one of the most common causes of heel pain. Imaging is essential for accurate diagnosis, with ultrasonography widely applied to evaluate PF thickness, monitor therapeutic outcomes, and guide interventions. However, its application is limited by operator dependency. This study aimed to investigate the inter- and intra-rater reliability of musculoskeletal ultrasound in measuring PF thickness in patients with plantar fasciitis.
Methods In this cross-sectional analytical study, 40 participants were enrolled, including 26 females and 14 males. The reliability of PF measurements on different sides was assessed using Cronbach’s alpha and intraclass correlation coefficients (ICC).
Results A total of 40 participants (age range: 20-60 years) were included in the study. PF thickness in patients with plantar fasciitis measured by Observer 1 ranged from 3.8-6.9 mm (left) and 3.2-6.0 mm (right), whereas measurements by Observer 2 ranged from 2.9-7.1 mm (left) and 3.2-6.0 mm (right). Intra-rater reliability showed ICCs ranging from 0.618-0.857 for Observer 1 and 0.76-0.92 for Observer 2, indicating moderate (> 0.60) to excellent reliability.
Conclusion PF is a deep structure, and its visualization may be influenced by operator technique. Ultrasound measurement of tendon thickness shows good reliability in patients with established plantar fasciitis.