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Interphalangeal Joints (Foot)

articulationes interphalangeae pedis

The toe interphalangeal joints are hinge joints that primarily flex the toes to grip the ground during push-off. The great toe has a single IP joint and the lesser toes have both PIP and DIP joints. Deformity at these joints, hammertoe (PIP flexion contracture), claw toe (MTP hyperextension with PIP flexion), and mallet toe (DIP flexion), produces painful corns from shoe friction and reduced toe ground contact for propulsion.

Anatomical Data

Structure

Bones	Phalangeal heads and bases of the lesser toes and great toe Great toe: one IP joint. Lesser toes 2-5: PIP and DIP joints
Ligaments	Medial and lateral collateral ligaments Plantar plates Extensor and flexor tendon insertions (EHL and FHL at the great toe)

Biomechanics

Function & Actions

Movements	PIP: flexion 35 degrees, minimal extension DIP: flexion 60 degrees

Clinical Relevance

Clinical Notes

The distinction between hammertoe (PIP flexion), claw toe (MTP hyperextension with PIP and DIP flexion) and mallet toe (DIP flexion from FDL tightness) guides surgical management. Flexible hammertoes may be corrected by resection arthroplasty of the proximal phalangeal head, while rigid deformities need PIP joint fusion. Mallet toe is treated by FDL tenotomy or DIP fusion. Claw toe correction often also needs MTP release or plantar plate repair. Rheumatoid arthritis commonly produces claw toes with MTP subluxation in the rheumatoid forefoot.

Pathology

Common Injuries & Conditions

Hammertoe Deformity

PIP flexion contracture producing dorsal PIP corn from shoe friction managed with shoe modification, toe padding, and surgical PIP joint arthrodesis for rigid deformities.

Claw Toe Deformity

MTP hyperextension with PIP and DIP flexion from intrinsic muscle weakness or neurological disease, causing dorsal and tip corns; corrected surgically at both the MTP and IP joints when footwear changes fail.

Mallet Toe

DIP flexion deformity from FDL tightness producing a painful corn at the toe tip, managed with padding or FDL tenotomy or DIP fusion.

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