A heel spur forms when repeated stress on the heel bone triggers your body to deposit new bone tissue at the point where soft tissue pulls against it. This process happens gradually, often over many months, and the bony growth itself is surprisingly common: 15 to 25% of the general population has heel spurs without any pain at all.
The Bone-Building Process Behind a Spur
Your heel bone (the calcaneus) is the largest bone in the foot, and it anchors the thick band of connective tissue that runs along the bottom of your foot, called the plantar fascia. When that attachment point experiences repeated pulling or strain, your body responds by laying down new bone in an attempt to reinforce the area.
This happens through a process called intramembranous ossification, where new bone forms directly on the surface of existing bone. Cells called osteoblasts deposit layers of mature, organized bone with rougher, newer bone on the outer surface. At the tip of the spur, a slightly different process can occur: cartilage forms first and is gradually replaced by bone, similar to how bones grow during childhood. The result is a small, pointed projection of calcium-rich bone extending from the underside or back of the heel. In patients studied with plantar fasciitis, the average spur measured about 4 millimeters long, though they can range from barely detectable to over 12 millimeters.
What Causes the Stress That Triggers Growth
The fundamental trigger is chronic mechanical strain at the spot where the plantar fascia or Achilles tendon attaches to the heel bone. Every time you take a step, these tissues pull against the bone. Normally that’s fine. But when the pulling force is excessive or sustained over long periods, the bone’s surface becomes irritated, and the body begins reinforcing that attachment point with new bone tissue.
Several factors increase this mechanical strain:
- Flat feet or high arches change how force distributes across the foot, concentrating more stress on the heel.
- Gait abnormalities caused by conditions affecting balance or coordination can shift extra pressure onto the heels with each step.
- Excess body weight increases the load on the plantar fascia with every stride.
- Prolonged standing or running on hard surfaces creates cumulative strain on the attachment point.
- Worn-out or unsupportive shoes fail to cushion or stabilize the heel, letting more force transfer directly to the bone.
The spur doesn’t appear overnight. It develops slowly as the body continues depositing bone in response to ongoing stress. By the time a spur shows up on an X-ray, it represents months or years of accumulated strain.
The Relationship Between Heel Spurs and Pain
Here’s the part that surprises most people: the spur itself usually isn’t what hurts. Most people who have bone spurs on their heels have no heel pain at all. Research comparing patients with and without plantar fasciitis found that 89% of those with plantar fasciitis had a calcaneal spur, compared to 32% of people without the condition. That’s a strong association, but separate studies in the general population have found spurs in 10 to 63% of people with no symptoms whatsoever.
The pain people associate with a heel spur nearly always comes from the inflamed soft tissue around it, particularly the plantar fascia. The American Academy of Orthopaedic Surgeons states this directly: heel spurs do not cause plantar fasciitis pain. When surgeons do operate on severe plantar fasciitis, they don’t usually remove the spur, because the spur isn’t the source of the problem. The spur is more like a marker that chronic strain has been happening in that spot.
How Heel Spurs Are Found
Because spurs are painless on their own, most are discovered incidentally during an X-ray taken for another reason, like investigating heel pain or checking for a stress fracture. On an X-ray, the spur appears as a small, pointed extension of bone projecting from the bottom or back of the heel.
When you visit a doctor for heel pain, the exam focuses less on whether a spur exists and more on identifying the actual source of pain. A physical exam typically checks for an area of maximum tenderness on the bottom of the foot just in front of the heel bone, limited upward flexibility in the ankle, and whether you have flat feet or high arches. The goal is to rule out other causes of heel pain, including stress fractures, nerve compression, or Achilles tendon problems, rather than to confirm the presence of a spur.
Managing the Underlying Problem
Since the spur is a consequence of chronic strain rather than the cause of pain, treatment targets the strain itself. Reducing pressure on the heel through supportive footwear, cushioned insoles, or orthotic inserts addresses the mechanical forces that caused the spur to form in the first place. Stretching the plantar fascia and calf muscles helps relieve the tension at the attachment point. For people whose gait contributes to the problem, adjusting walking patterns to distribute weight more evenly across the foot can make a meaningful difference.
Most heel pain associated with spurs improves with these non-surgical approaches. The spur itself doesn’t go away, but it doesn’t need to. It’s a permanent remodeling of the bone that, once the surrounding inflammation resolves, typically causes no problems on its own.