48-year-old female with fluctuating pain in different areas of the foot. The pain is not continuously localized to one specific point and varies in location and intensity. A mild flatfoot posture is suspected. The patient previously benefited from insoles, but these are no longer available.
Ultrasound examination demonstrates abnormalities at the level of the spring ligament, also known as the plantar calcaneonavicular ligament. The ligament is locally hypoechoic and contains an anechoic zone, compatible with a possible partial tear or degenerative fibre disruption.
This finding may be related to a mild pes planus alignment, in which increased loading of the medial longitudinal arch can increase traction forces on the spring ligament.
In addition, there is midportion Achilles tendinopathy. Based on the reported symptom pattern, this finding may currently be of limited clinical relevance, as the patient does not describe a clearly localized pain point at the Achilles tendon.
The overall clinical picture is characterized by variable, shifting foot pain rather than a single reproducible focal pain location.
1. Final diagnosis
Sonographic abnormalities of the spring ligament, with suspicion of a partial tear or degenerative change of the plantar calcaneonavicular ligament. The clinical relevance of this finding is uncertain and should be correlated with targeted examination of the medial longitudinal arch, hindfoot alignment, tibialis posterior function, and pain-provoking loading tests. Additional midportion Achilles tendinopathy is present, but this may not be the primary pain generator unless local Achilles pain is clinically reproducible.
2. Differential diagnosis
The findings may reflect medial arch overload with irritation or partial injury of the spring ligament, possibly related to mild pes planus. Differential diagnoses include early progressive flatfoot deformity, tibialis posterior dysfunction, local medial arch instability, or nonspecific overload of the medial foot structures. Given the fluctuating and shifting pain pattern, functional load-related symptoms, footwear or insole-related factors, compensatory overload elsewhere in the foot, referred pain from the ankle or lower leg, and less likely neurological or systemic causes should also be considered.
3. Teaching points
The spring ligament is an important stabilizer of the medial longitudinal arch and supports the talar head. Ultrasound abnormalities such as focal hypoechogenicity and an anechoic intraligamentous zone may suggest degenerative change or partial tearing, but clinical correlation is essential. A mild flatfoot posture can increase medial arch load and traction on the spring ligament. Incidental tendon abnormalities, such as midportion Achilles tendinopathy, should only be considered clinically relevant when symptoms are reproducible at that structure.
4. Injury/disease information
Spring ligament injury or degeneration may contribute to medial foot pain and progressive flattening of the medial arch, particularly when associated with altered hindfoot alignment or tibialis posterior dysfunction. Assessment should include foot posture, hindfoot valgus, medial arch stability, gait, footwear, and the function of the tibialis posterior tendon. Supportive insoles may reduce traction load on the spring ligament and improve medial arch mechanics. MRI may be useful when symptoms persist or remain poorly localized, as it can better assess the spring ligament, tibialis posterior tendon, cartilage, and deeper intra-articular or osseous structures.
Marc is founder of, and trainer at, SonoSkills. SonoSkills is an organization dedicated to MSK ultrasound education. He's also an MSK Sonographer at EchoConsult in Roermond, the Netherlands.
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