Α 45-year-old man, trained in martial arts, was referred to our hospital with 1 month ankle pain. Physical examination revealed swelling of the ankle without any inflammation sings. Imaging studies were requested with the suspicion of an osteochondral lesion.
No fracture was evident at plain radiography. A poorly defined os naviculare was detected (Fig. 1). The CT examination did not show any fracture or osteochondral talar lesion. An anatomical variant consisting of a multiossicle Type 1 os naviculare was shown (Fig. 2, 3).
Due to non-specific findings to explain the persistent ankle pain, an MRI examination was performed with a 1.5 Tesla scanner. MRI showed bone marrow oedema located in the anterior talus which enhanced following intravenous administration of gadolinium contrast (Fig. 4). No fracture line or other subarticular focal lesion was disclosed within the oedematous area. In both CT and MRI, the os naviculare was located eccentrically within the distal course of the posterior tibialis tendon.
In conclusion, pain was assigned to transient osteoporosis of talus (transient bone marrow oedema syndrome) and the respective anatomic variant was an incidental finding.
A. It is accepted that the accessory navicular bone (AN) is an anatomic variant. AN represents failure of the navicular secondary ossification centre to unite during childhood. There are few reports supporting that AN may be inherited. AN is considered as the most common accessory bone of the foot [1, 2]. It is classified in 3 types. Type 1 is a small, accessory bone usually located in the medial posterior aspect of the navicular within the posterior tibialis tendon (PTT). Type 2 is a larger bone with an irregular shape which is attached to the navicular with a synchondrosis. Type 3 is a fused accessory bone, which is producing a cornuate navicular [3]. A multiossicle appearance AN has been recently reported, as it was in our case [1].
B. Type 1 and 3 are usually asymptomatic. In contrast, Type 2 is often symptomatic. Young athletes may present with a symptomatic AN during sports activities. In this clinical scenario, the physical examination typically reveals tenderness over the prominence on the medial aspect of the midfoot. Symptomatic AN is typically seen in childhood or in early adulthood as a result of pressure of the accessory bone against shoes. Types 1 and 2 AN are associated with a progressive flattening of the longitudinal arch [4].
AN could be seen incidentally in routine radiologic examinations. The 45ο external oblique view is required in order to better differentiate the AN from a small fracture. In the presence of pain and tenderness in the medial aspect of the foot, the proper interpretation of the imaging studies will obviate further imaging or inaccurate treatment [3]. Radiologist should suggest the clinical impact of an anatomic variant. In the case presented herein, the multiossicle os naviculare type I, was irrelevant to the clinical symptoms.
C. Type 1 AN is a small ossicle within the distal PTT. On CT and MRI, the presence of the os within the tendon is diagnostic.
D. AN type I requires no treatment if asymptomatic. If symptomatic, preoperative MRI will guide the tendon reconstruction. In our case, pain was attributed to bone marrow oedema and thus treatment was focused to alleviate weight bearing.
E. The multiossicle appearance of AN type I, has been recently reported. Its presence is unlike to cause symptoms. Proper recognition of this entity will obviate unnecessary therapeutic procedures.
Multiossicle os naviculare
Based on the provided X-ray, CT, and MRI images, the main features are as follows:
• Multiple small bony fragments can be observed in the medial proximal region of the talus (medial proximal navicular), with a regular shape and connected to the main navicular by cartilage or fibrocartilage;
• CT shows these small fragments are located within (or adjacent to) the posterior tibial tendon, exhibiting bone density similar to that of the navicular body;
• MRI reveals low-to-medium signal changes of these small bony structures near the posterior tibial tendon, with mild signal changes in the adjacent navicular bone, but no significant signs of inflammation or soft tissue swelling overall;
• No obvious bony destruction or clear evidence of articular surface fracture is observed;
• The patient’s ankle joint also shows signs of bone marrow edema, suggesting local stress or excessive loading.
Based on the patient’s training background (frequent martial arts, jumping, or high-intensity exercise) and the imaging findings, potential diagnoses or differential diagnoses include:
Considering the patient’s age, duration of symptoms, imaging findings, and training background:
• These multisegmented navicular variations (multi-fragment accessory navicular Type I) are congenital anatomical variants and are not directly related to the current ankle pain;
• The present symptoms are more likely related to excessive loading of the foot and ankle, localized bone marrow edema, or mild stress-induced changes;
• Therefore, the final diagnosis is: “Multisegmented Accessory Navicular Type I (Asymptomatic Accessory Navicular), with Pain Due to Bone Marrow Edema in the Ankle Joint”.
Treatment Strategy:
• Conservative Management: For an asymptomatic or mildly symptomatic Type I accessory navicular, no special treatment is necessary. If bone marrow edema causes pain, short-term reduction in weight-bearing, limiting intense training, and the use of anti-inflammatory and analgesic medications (e.g., NSAIDs) or physical therapy (cold compresses, ultrasound therapy, etc.) may be considered;
• Orthotic Devices and Arch Support: If the patient has a relatively flat arch or engages in high-intensity training, using arch supports early in rehabilitation can help reduce stress on the posterior tibial tendon insertion;
• Surgical Indications: If persistent cartilage damage or posterior tibial tendon issues (e.g., recurrent tenosynovitis, partial tendon tear) occur and do not respond to conservative management, surgical intervention may be considered. However, this applies only to a very small number of cases in this context.
Rehabilitation and Exercise Prescription (FITT-VP Principle):
• Frequency (F): 3-4 times per week, avoiding multiple consecutive days of high-intensity ankle loading;
• Intensity (I): From light to moderate intensity. Initially avoid prolonged running, jumping, or martial arts kicking. Begin with low-impact activities such as swimming or cycling;
• Time (T): 20-30 minutes per session, gradually increasing as symptoms improve;
• Type (T): Gradually implement resistance training, focusing on strengthening the foot and lower leg muscles (e.g., posterior tibial muscle, soleus) and core stability exercises;
• Progression (P): After pain and bone marrow edema improve, gradually resume normal martial arts training under professional supervision. Closely monitor for any new or worsening medial foot pain;
• Volume and Progression (VP): Maintain appropriate exercise volume at each stage, gradually increasing intensity and duration based on individual recovery. If other lower limb joint issues or cardiopulmonary limitations exist, conduct training under medical or rehabilitation expert supervision.
Disclaimer:
This report is based on the current imaging and clinical information available and is intended as a reference analysis. It does not replace in-person consultation or further evaluation by a healthcare professional. If symptoms persist or worsen, please seek medical advice promptly and follow the guidance of a qualified physician.
Multiossicle os naviculare
