Causes of Hammer Toe
Hammer toe results from muscular imbalance between intrinsic and extrinsic foot muscles, leading to flexion deformity at the proximal interphalangeal joint, with contributing factors including improper footwear, genetic predisposition, trauma, neuromuscular disorders, diabetic neuropathy, and plantar plate attenuation. 1, 2, 3
Primary Pathophysiologic Mechanism
The fundamental cause is an imbalance between the muscles and tendons that control toe movement, specifically between intrinsic and extrinsic foot musculature 1, 3. This imbalance creates:
- Marked flexion of the proximal interphalangeal joint 2
- Extension deformity at the metatarsophalangeal joint 2, 4
- Attenuation and subsequent rupture of the plantar plate 2
Specific Contributing Factors
Footwear-Related Causes
- Ill-fitting footwear is a major extrinsic cause, particularly shoes that crowd or compress the toes 1, 3
- Improper shoe wear creates chronic pressure that perpetuates the muscular imbalance 3
Structural and Genetic Factors
- Genetic predisposition plays a significant role in susceptibility 1, 3
- Foot deformities including hallux valgus, prominent metatarsal heads, pes cavus, and pes planus can contribute to hammer toe development 5
- Midfoot and hindfoot deformities (cavus foot, varus hindfoot, valgus hindfoot with forefoot pronation) may be present as associated conditions 3
Medical Conditions
- Neuromuscular disorders are an important underlying cause 1, 3
- Diabetic neuropathy specifically contributes to hammer toe formation through nerve damage affecting muscle balance 1
- Inflammatory arthritis can lead to joint changes that promote deformity 3
- Metabolic diseases may contribute to the development of lesser toe deformities 3
Traumatic Causes
Clinical Significance in High-Risk Populations
In patients with diabetes, hammer toes represent a foot deformity that significantly increases risk for ulceration 5. These structural abnormalities create:
- Increased plantar pressure at specific points 5
- Friction points that lead to callus formation and potential ulceration 5
- Joint immobility that compounds pressure distribution problems 5
Common Pitfalls
Do not overlook underlying neuromuscular or metabolic conditions when evaluating hammer toe, as these may require specific management beyond the deformity itself 1, 3. In diabetic patients with loss of protective sensation, hammer toes place the foot at moderate to high risk for foot ulcer development, requiring referral to therapeutic footwear specialists 5.