Medical Imaging Analysis Report

I. Radiological Findings

Based on the provided anteroposterior and lateral X-ray images of the ankle, the following can be observed:

• In the lateral aspect of the foot, between the calcaneus (Calcaneus) and the cuboid (Cuboid), there is an approximately 1.5 cm oval-shaped density located near the peroneus longus tendon (Peroneus longus tendon).
• This bony density has a well-defined boundary, showing clear demarcation from surrounding bone structures.
• No obvious acute fracture lines are seen in the local articular surface or within the tendon pathway. However, there is a slightly irregular change at the contact surface between this small bone and the cuboid, suggesting possible friction or restricted gliding in this region.
• The main ankle joint surface appears generally normal, with no clear signs of acute traumatic fracture.

II. Potential Diagnoses

Taking into account the patient's age, MRI/X-ray imaging findings, and medical history, the following are possible diagnoses or differential diagnoses:

• Os peroneum (fibularis longus tendon sesamoid): A common accessory or sesamoid bone located in the peroneus longus tendon. It is usually asymptomatic but can cause pain or tendon issues. It can be present in normal individuals and may be bilateral.
• Os peroneum-related pathology: If it impedes tendon movement, or if there is an avulsion or fracture, it may lead to localized pain and swelling.
• Other accessory or sesamoid bones (such as Os vesalianum, Os trigonum, etc.): Relevant to other foot attachment sites and joint surfaces. Given the location seen on these images, they are less likely compared to the current finding.
• Small avulsion fracture: If trauma was involved, the force from the tendon may cause a small bone fragment to be avulsed and misinterpreted as an Os peroneum. However, the well-defined bony boundaries on imaging suggest an accessory bone.

III. Most Likely Final Diagnosis

Considering the patient's clinical symptoms (right ankle pain, swelling) in conjunction with the imaging findings, the most probable diagnosis is:

“Os peroneum (fibularis longus tendon sesamoid) with localized friction or restricted gliding.”

This is due to the accessory bone’s unique position in the ankle structure, which can easily lead to friction with surrounding bone or cause pain following trauma. If there is any doubt about other soft tissue lesions or the presence of minor avulsion or tendon pathology, further MRI (soft tissue sequence) evaluation may be considered.

IV. Treatment Plan and Rehabilitation

Based on the current diagnosis and the patient’s age and symptoms, possible treatment options include:

• Conservative treatment:
  • During acute pain and swelling, weight-bearing on the affected side should be reduced. A brace or crutches may be used to rest the joint briefly.
  • Local cold compresses or nonsteroidal anti-inflammatory drugs (NSAIDs) can be used to relieve pain and inflammation.
• Physical therapy and rehabilitation training:
  • Once pain has significantly subsided, mild ankle joint movements—such as active dorsiflexion, plantarflexion, and circumduction—can be performed to improve blood circulation and tendon gliding in the peroneus longus.
  • Gradually increase lower limb muscle strength training, focusing on the arches of the foot and overall ankle stability. Exercises may include inversion and eversion with resistance bands.
  • The frequency of these exercises may start at 1–2 sessions per day, each lasting about 10–15 minutes. Intensity and duration should be increased gradually based on improvement (following the FITT-VP principle).
• Surgical indication:
  • If conservative treatment proves ineffective or if severe pain or tendon injury is present, surgical exploration and repair could be considered.
  • However, in most cases, pain caused by an Os peroneum can be alleviated through conservative management.
• Exercise prescription and progression:
  • Early stage: Focus on pain relief and regaining basic range of motion by performing 5–10 minutes of ankle joint flexion-extension and inversion-eversion exercises daily.
  • Middle stage: Strengthen nearby muscle groups, such as the fibularis muscles, using resistance bands. Gradually increase resistance, with daily sessions of 10–15 minutes divided into sets.
  • Later stage: Once symptoms have substantially improved, progress to light jogging and ankle flexibility and balance exercises (e.g., single-leg stance or balance board training) daily or on alternate days, extending training duration as tolerated.
  • If other joint or bone risks are present, training should be carried out under professional supervision to ensure safety.

Disclaimer: This report is intended as a reference for medical analysis and does not replace an in-person consultation or professional medical advice. If you experience any discomfort or have further questions, please seek prompt medical attention and follow the diagnoses and treatment recommendations of a specialist.