Hammer toes and bunions share many of the same root causes: inherited foot structure, muscle imbalances, poorly fitting shoes, and certain medical conditions. They also tend to show up together, since a bunion on the big toe can crowd the smaller toes and push them into the bent position that defines a hammertoe. Bunions affect about 23% of adults between 18 and 65, with that number climbing to 36% in people over 65. Hammertoes are nearly as common, particularly in the second toe.
How Each Deformity Forms
A bunion develops at the base of the big toe, where the toe meets the foot. The joint gradually shifts out of alignment: the big toe drifts toward the smaller toes while the head of the long bone behind it (the first metatarsal) pushes outward, creating the visible bump on the inside of the foot. As the deformity progresses, the ligaments on the inner side of the joint weaken and stretch. The tendons that normally hold the toe straight follow the deviation, pulling the toe further out of line and creating a self-reinforcing cycle. Eventually the metatarsal head slips off its normal cushioning platform (a pair of small bones called sesamoids that sit underneath the joint), which accelerates the misalignment.
A hammertoe forms differently. Your smaller toes are controlled by two sets of muscles: small intrinsic muscles inside the foot and larger extrinsic muscles in the lower leg. When the small muscles weaken or can’t do their job, the larger muscles overpower them. The result is a toe that bends upward at the base and curls downward at the middle joint, creating the hammer shape. No flexor tendon inserts directly into the first bone of the smaller toes, so once the balance tips in favor of the longer, stronger tendons, nothing opposes the bending force at the middle joint.
Inherited Foot Structure
Genetics is one of the strongest risk factors for both conditions. You don’t inherit a bunion or hammertoe directly, but you can inherit the foot shape that makes one likely. Flat feet, unusually flexible joints, a long second toe, and the overall width and arch of your foot all run in families. A foot with a low arch, for example, places more stress on the inner side of the forefoot with every step, gradually pushing the big toe joint out of alignment. A second toe that’s longer than the big toe gets jammed into the front of shoes more easily, setting the stage for a hammertoe.
If your parents or grandparents had bunions, your risk is meaningfully higher regardless of what shoes you wear. That said, genetics loads the gun while other factors pull the trigger.
Footwear and Repetitive Stress
Shoes with a narrow toe box compress the toes together for hours at a time. This forces the big toe into a valgus position (angled toward the other toes) and pushes the smaller toes into a flexed, curled posture. High heels add another layer of risk by shifting body weight onto the ball of the foot, increasing pressure on the forefoot by a factor of two or more depending on heel height. That sustained forefoot loading weakens the ligaments and small muscles that keep toes properly aligned.
This doesn’t mean shoes alone cause these deformities. Populations that rarely wear shoes still develop bunions, which points back to genetics and biomechanics. But tight, narrow, or high-heeled footwear accelerates the process in someone who’s already predisposed. Years of repeated stress on the joint can turn a mild structural tendency into a visible deformity.
Arthritis and Inflammatory Conditions
Rheumatoid arthritis is a particularly strong driver of both bunions and hammertoes. In RA, immune cells migrate to the joint lining and cause chronic inflammation. Over time, this creates abnormally thick tissue that erodes cartilage and damages the surrounding ligaments and tendons. Joints lose their shape and alignment. In the foot, this erosion can cause the big toe joint to shift or even dislocate, forming a bunion and crowding the smaller toes into hammertoe positions.
Osteoarthritis can contribute as well, though through a different mechanism. Rather than immune-driven erosion, the cartilage simply wears down with age and use, changing how forces distribute across the joint and allowing the bones to drift out of position.
Nerve Damage and Muscle Weakness
Any condition that damages the nerves supplying the small muscles in your feet can trigger hammertoes. Diabetes is the most common culprit. Peripheral neuropathy from diabetes gradually weakens the intrinsic foot muscles while leaving the larger calf muscles relatively unaffected. This creates exactly the kind of imbalance that causes toes to curl: the strong flexor tendons from the leg pull the middle and end joints downward with no opposing force from the now-weakened small muscles.
Other neurological conditions, including Charcot-Marie-Tooth disease and stroke, can produce the same pattern. The common thread is any process that selectively weakens the small stabilizing muscles of the foot while the larger muscles in the lower leg keep working.
Bunions Can Cause Hammertoes
One important detail many people miss: bunions and hammertoes aren’t just fellow travelers with shared risk factors. A bunion can directly cause a hammertoe. As the big toe angles toward the second toe, it physically pushes the second toe upward and out of position. The second toe, now displaced, gets locked in a flexed posture. Over months and years, what starts as a crowding problem becomes a fixed deformity as the tendons and joint capsule adapt to the new position.
This is why the second toe is the most common site for hammertoes, and why people with moderate to severe bunions so often develop them.
How These Deformities Progress
Both conditions start flexible and become rigid over time. An early hammertoe can still be straightened by hand. The toe bends when you stand but can be pushed back into position. At this stage, the problem is muscular and tendinous, not structural. Left alone, the joint capsule and surrounding soft tissues gradually tighten and scar, locking the toe in its bent position permanently.
Bunions follow a similar trajectory. Clinicians measure severity by the angle between the big toe and the metatarsal bone. A normal angle is under 15 degrees. Mild bunions fall between 15 and 30 degrees, moderate between 30 and 40, and severe bunions exceed 40 degrees. As the angle increases, the metatarsal head rotates further off its sesamoid platform, the muscle vectors become more abnormal, and the deformity becomes harder to manage without surgery.
Corns, Calluses, and Other Complications
As toes shift out of alignment, new pressure points develop. The raised middle joint of a hammertoe rubs against the top of your shoe, and the tip of the curled toe presses into the sole. The bony bump of a bunion grinds against the shoe’s inner wall. Your skin responds to this repeated friction by thickening into corns and calluses, which are concentrated patches of hardened skin over bony prominences.
These aren’t just cosmetic annoyances. Corns can become painful enough to change how you walk, and in people with diabetes or poor circulation, they can break down into open sores that are vulnerable to infection. In severe cases, infected corns over hammertoes have led to bone infections. The deformities also shift how weight distributes across the ball of the foot, sometimes causing pain under the second or third metatarsal heads, a condition called metatarsalgia.
Who’s Most at Risk
Women develop bunions and hammertoes significantly more often than men, partly due to footwear patterns and partly due to differences in ligament laxity and foot structure. Age is another major factor: the prevalence of bunions nearly doubles after age 65 compared to younger adults, and hammertoes follow a similar curve. Higher body weight increases forefoot loading with every step. People with flat feet or very high arches both face elevated risk, though through different mechanical pathways. And anyone with a family history of these deformities should pay close attention to early signs, since catching either condition while it’s still flexible gives you the most options for slowing it down.