Non-Painful Swelling at Base of 5th Metatarsal
For non-painful swelling at the base of the 5th metatarsal without trauma history, obtain standard three-view radiographs first to rule out occult fracture, accessory ossicle, or other bony pathology, then proceed with MRI if radiographs are negative to evaluate for soft tissue masses, bone marrow edema, or tendon pathology. 1, 2
Initial Diagnostic Approach
Radiographic Evaluation
- Obtain anteroposterior, lateral, and mortise views that include the base of the fifth metatarsal as the initial imaging study 2, 3
- Weight-bearing radiographs provide additional information about structural stability and alignment 2, 4
- Standard radiographs have limited sensitivity for occult fractures and soft tissue pathology, particularly in the absence of pain 1
Advanced Imaging When Radiographs Are Negative
MRI is the preferred next step for non-painful swelling with negative radiographs because it allows:
- Visualization of bone marrow edema patterns that indicate occult fractures 1
- Detection of radiographically occult fifth metatarsal fractures (Jones fractures) 1
- Optimal assessment of accessory ossicles and their synchondrosis 1
- Evaluation of associated tendon pathology 1
- Clear demonstration of soft tissue masses or inflammatory processes 1
CT imaging may be considered as an alternative if MRI is contraindicated, though it has limited ability to assess soft tissue pathology and bone marrow edema compared to MRI 1
Differential Diagnosis Considerations
Accessory Ossicles
- MRI has replaced bone scans for evaluating symptomatic accessory ossicles 1
- Accessory ossicles are present in 4% of asymptomatic subjects, so correlation with clinical presentation is essential 1
- High-resolution ultrasound can assess stability of the synchondrosis dynamically and allow direct clinical correlation 1
Occult Fractures
- Fifth metatarsal occult fractures can present with minimal or no pain initially 1
- MRI demonstrates bone marrow edema that improves detection when radiographs are inconclusive 1
- Dual-energy CT has 98% sensitivity and 93% specificity for detecting bone marrow edema if MRI is unavailable 1
Soft Tissue Pathology
- Tendon pathology associated with the peroneus brevis insertion can cause swelling at the base of the 5th metatarsal 1
- Power Doppler ultrasound can identify increased blood supply in inflammatory conditions 1
Treatment Algorithm Based on Imaging Findings
If Occult Fracture Identified
- Non-displaced fractures: functional treatment with CAM-walker boot or hard-soled shoe for 7-9 weeks 5, 6
- Displaced fractures or those involving >30% of the cubometatarsal joint: orthopedic referral for potential surgical management 7
If Accessory Ossicle or Soft Tissue Pathology
- Conservative management with activity modification and supportive footwear 1
- Physical therapy for associated tendon dysfunction 2
If All Imaging Negative
- Observation with clinical follow-up
- Consider inflammatory or systemic causes if swelling persists
Common Pitfalls
- Do not assume absence of pain means absence of pathology - occult fractures and accessory ossicles can be minimally symptomatic initially 1
- Avoid relying solely on radiographs when clinical suspicion exists, as they miss one-third of foot fractures 1
- Do not perform unnecessary knee radiographs in isolated 5th metatarsal presentations 3
- In diabetic patients, maintain high suspicion for neuropathic changes that may mask pain despite significant pathology 4, 3