Causes / typical injury mechanism: Freiberg disease is a form of avascular necrosis (AVN) that affects the metatarsal head. Although the exact underlying cause is unknown, symptoms are triggered by trauma from weight-bearing activities such as walking or by vascular insufficiency. The condition is associated with genetics, lifestyle, and environmental factors.

Triggering events include:

• Trauma – Repeated trauma or gradual overload of the dorsal aspect of the joint.
• Abnormal biomechanics – Hyperdorsiflexion, often due to high-heeled footwear.
• Arterial insufficiency – Anatomic variants of dorsal and plantar metatarsal arteries may predispose metatarsals to ischemia.

Classic history and presentation: Patients complain of insidious onset of pain in the plantar forefoot, most commonly at the level of the second MTP joint. Pain is exacerbated when ambulating barefoot or in footwear with elevated heels or poor rigidity.

Prevalence:

• Age – This is most common in adolescents, but it can occur at any age.
• Sex / gender – This is more common in females.

Risk factors:

• Female sex
• Wearing high-heeled shoes

Grade / classification system: Smillie classification

• Stage 1: A fissure in the epiphysis with observable sclerosis between cancellous surfaces.
• Stage 2: Absorption of cancellous bone into the proximal metatarsal head. Sinking of the articular cartilage dorsally.
• Stage 3: Further absorption of cancellous bone and sinking of the articular cartilage. Medial and lateral bone projections can be seen.
• Stage 4: Deeper sinking of the articular cartilage with possible fracture of medial and lateral projections.
• Stage 5: Joint arthrosis characterized by flattening and/or deformity of the metatarsal head. The plantar aspect of the metatarsal head is involved. Thickening of the metatarsal bone shaft is seen.