1. Imaging Findings

This patient is a 42-year-old female presenting with pain and local swelling in the plantar forefoot area of the left foot (primarily at the second metatarsophalangeal joint). Based on the provided MRI and ultrasound images, the following key features are noted:

• MRI Imaging: Near the plantar side of the second metatarsophalangeal joint adjacent to the plantar plate, the originally low-signal fibrocartilaginous structure is replaced by a localized high-signal lesion, suggesting possible disruption of the fibrous continuity. Sagittal sequences help assess tear thickness, while coronal sequences are more useful for localizing the tear.
• Ultrasound Imaging: The normally homogeneous plantar plate structure shows a focal hypo-echoic (low echo) defect at the distal attachment, indicating a possible partial or full-thickness fiber tear. This commonly occurs near the attachment site on the proximal phalanx, consistent with typical plantar plate tear locations.
• Local Soft Tissue Condition: Mild soft tissue swelling is visible around the joint, and the joint capsule and supporting ligaments may be strained or exhibit inflammatory changes.

2. Potential Diagnoses

Based on the patient’s frequent use of high heels, the forefoot (metatarsal head) pain, and the imaging findings indicating joint instability and plantar plate fiber damage, the possible diagnoses include:

1. Partial or Full-Thickness Tear of the Plantar Plate: The plantar plate is located under the metatarsophalangeal joint and is crucial for joint stability. Frequent high heel wear leads to excessive pressure on the forefoot and repetitive microtrauma. A tear would appear as a localized high signal on MRI and a hypo-echoic defect on ultrasound, consistent with the clinical and imaging findings.
2. Morton’s Neuroma: Usually presents with intermetatarsal pain, commonly affecting the 3rd and 4th interspaces but can sometimes involve the 2nd and 3rd. MRI or ultrasound may show localized thickening of the intermetatarsal nerve sheath. Patients often report numbness or burning pain, and pain can be elicited by squeezing the foot, which is less typical for this case.
3. Freiberg’s Infraction (Freiberg Disease): Commonly involves osteonecrosis of the second or third metatarsal head. MRI may show bone marrow edema or collapse of trabeculae. Patients often experience pain in the metatarsal head that worsens with activity, and imaging typically reveals bony changes. This case does not clearly indicate bone collapse or necrosis.
4. Joint Capsule or Synovial Cyst: A cystic mass can be found around the joint; ultrasound may show anechoic or hypo-echoic areas, and MRI may show a cystic signal. However, the main abnormality here is focused on the course of the plantar plate fibers, making an isolated cystic lesion less likely.

3. Final Diagnosis

Taking into account the patient’s age, occupational factors (prolonged high heel use resulting in increased forefoot pressure), clinical symptoms (pain and instability at the second metatarsophalangeal joint), and imaging findings (MRI and ultrasound indicating disruption and hypo-echoic defects in the plantar plate fibers), the most likely diagnosis is:

A partial or full-thickness tear of the plantar plate at the second toe (Plantar Plate Tear).

4. Treatment Plan and Rehabilitation

4.1 Treatment Overview

• Conservative Treatment:
  • Reduce factors that cause excessive load on the plantar plate, such as avoiding prolonged use of high heels and opting for wider footwear with arch support.
  • Use protective insoles or orthotic devices to relieve local pressure on the forefoot and prevent further plantar plate damage.
  • Apply local anti-inflammatory and analgesic treatments or use physical modalities (e.g., ultrasound therapy, ice packs, iontophoresis) to reduce inflammation and pain.
• Surgical Treatment:
  • Indicated if conservative management fails, or if there is significant joint instability or deformity of the metatarsophalangeal joint. Surgical repair of the plantar plate combined with soft tissue stabilization may be considered.

4.2 Rehabilitation and Exercise Prescription

Rehabilitation should follow a gradual, individualized approach, guided by the FITT-VP principle:

• Type of Exercise: Begin with non-weight-bearing or low-impact activities such as swimming, passive joint mobilization in a seated position, or resistance band exercises. Progress to light weight-bearing walking in the intermediate phase, and eventually resume daily walking and light jogging if tolerated in the final phase.
• Frequency: It is recommended to perform low-intensity exercises 3–5 times per week initially, increasing to short daily sessions as tolerated and based on pain and recovery.
• Intensity: Start at a low intensity to avoid repeated stress that can cause re-injury. Increase resistance or load gradually, following pain feedback and medical advice.
• Time: Begin with 10–20 minutes per session, increasing to around 30 minutes as tolerated.
• Progression: Transition from low-intensity to moderate-intensity exercise, maintaining protective support for the affected joint (such as arch supports or bracing). If significant pain or swelling occurs, reduce the exercise intensity immediately and seek further evaluation.

Special Considerations: For patients with particularly fragile feet or marked forefoot pain, it is important to evaluate lower limb alignment and arch integrity. Those with cardiac or pulmonary issues or other comorbidities should consult healthcare professionals for a more cautious exercise plan.

Disclaimer: This report is a reference analysis based on the provided information and does not replace an in-person medical consultation or professional medical opinion. For any concerns or changes in condition, please seek prompt medical attention or consult a specialist.