Can the Navicular Bone Swell?
Yes, the navicular bone can absolutely become swollen, and this swelling is clinically significant enough to be included in diagnostic criteria for midfoot fractures. 1
Clinical Significance of Navicular Swelling
The ACR Appropriateness Criteria explicitly incorporates navicular swelling into the Ottawa rules for foot trauma 1. When swelling is added as a criterion to the standard Ottawa rules, the sensitivity for detecting fractures increases to 100% in the malleolar zone and 50% in the midfoot, with specificities of 55% and 40% respectively 1. This means point bone tenderness OR swelling of the navicular bone warrants radiographic evaluation when there is midfoot pain.
Pathologic Conditions Causing Navicular Swelling
In Children
- Köhler Disease presents with pain and swelling of the medial midfoot between ages 2-10 years, caused by avascular necrosis of the tarsal navicular 2
- Boys are more commonly affected than girls
- Radiographs show increased sclerosis, flattening, and fragmentation
In Adults and Athletes
- Transient osteoporosis (bone marrow edema syndrome) can affect the navicular, causing swelling and pain 3
- Particularly seen in high-level athletes
- Self-limiting but can significantly impact performance
Symptomatic Accessory Navicular
- Type II os naviculare with bone marrow edema causes localized swelling and pain 4
- 100% of patients with bone marrow edema localize pain to the medial midfoot
- Soft tissue edema overlying the os naviculare correlates with more severe pain 4
- The accessory navicular occurs in approximately 17.5% of patients and is bilateral in 50% of cases 5
Rare Causes
- Chondroblastoma can present with firm swelling after minor trauma 6
- Requires imaging (CT/MRI) and pathologic confirmation
Clinical Pitfall
Do not dismiss navicular swelling as insignificant. The Ottawa rules specifically include swelling because it increases diagnostic sensitivity for fractures. When evaluating midfoot trauma, palpate for both point tenderness AND observe for localized swelling over the navicular bone, as either finding mandates imaging 1.