Plantar Ganglion Cyst of the Midfoot: Definition and Clinical Significance
A plantar ganglion cyst of the midfoot is a benign, fluid-filled cystic lesion arising from joint capsules or tendon sheaths on the plantar (bottom) surface of the midfoot, which is clinically significant because it can cause pain, nerve compression, and even stress fractures of adjacent metatarsal bones.
Key Characteristics
Plantar ganglion cysts are rare compared to dorsal foot ganglions, occurring deep beneath the plantar fascia, making them difficult to palpate on clinical examination. 1, 2 These cysts can extend from the dorsal to plantar compartments in an "hourglass" configuration, requiring careful preoperative imaging assessment. 3
Clinical Presentation
- Pain and swelling in the midfoot region, though the mass may not be palpable due to its deep location beneath the plantar fascia 2
- Nerve compression symptoms including hypoesthesia, numbness, tingling, and positive Tinel's sign when the cyst compresses the medial plantar nerve 4
- Atypical metatarsal changes on radiographs, including cortical thinning, pressure indentations, or stress reactions in adjacent metatarsal bones 1, 2
Diagnostic Approach
Ultrasound is useful for confirming fluid content in suspected ganglion cysts in the appropriate clinical setting, demonstrating characteristic features of encapsulated cystic masses. 5 However, US diagnostic accuracy drops considerably for deep-seated lesions in anatomically complex areas like the midfoot. 5
MRI is the most sensitive imaging modality for plantar midfoot ganglion cysts, particularly when radiographs show atypical bone changes or when planning surgical excision. 6, 1, 2 MRI accurately characterizes:
- The cystic nature and extent of the lesion 3
- Associated stress fractures or stress reactions in metatarsals 1, 2
- Nerve compression and relationship to neurovascular structures 4
- Potential hourglass extensions between compartments 3
Important Clinical Pitfalls
When plain radiographs show atypical metatarsal bone morphology—such as cortical thinning, pressure indentations, or stress reactions—a ganglion cyst should be suspected and MRI should be obtained. 1, 2 The ganglion can cause:
- Structural bone weakness from pressure erosion 2
- Stress fractures from combined mechanical factors including bony absorption, altered loading patterns, and underlying osteoporosis 2, 7
Treatment Considerations
Complete surgical excision of the ganglion cyst with surrounding periosteum is recommended to prevent recurrence, particularly when conservative management fails or when associated with stress fractures. 2, 8
- Aspiration alone may be successful in some cases, allowing associated stress fractures to heal with conservative treatment 7
- Combined dorsal and plantar surgical approaches may be necessary for hourglass-shaped cysts extending between compartments 3
- Stress fractures typically heal completely following cyst resection 1, 2
For patients with isolated plantar neuropathy symptoms where conservative treatment is ineffective, foot imaging with MRI and electrophysiological studies should be considered to exclude space-occupying lesions like ganglion cysts. 4