Heel pain that shows up in only one foot is almost always caused by a localized mechanical problem rather than something systemic. The most common culprit is plantar fasciitis, which affects one foot at a time in the majority of cases. But several other conditions can produce similar symptoms, and telling them apart matters because the treatments differ. Here’s what could be going on and how to narrow it down.
Plantar Fasciitis: The Most Likely Cause
Plantar fasciitis is inflammation of the thick band of tissue that runs along the bottom of your foot, connecting your heel bone to your toes. It’s the single most common reason people develop heel pain, and most people experience it in one foot at a time.
The hallmark symptom is pain with your first steps in the morning or after sitting for a while. That initial sharpness tends to ease after a few minutes of walking as the tissue loosens up, then returns as a dull, constant ache if you stay on your feet for long periods. You may also notice stiffness, arch pain, or swelling around the heel. The pain is typically worst right where the tissue attaches to your heel bone, toward the inside edge of the bottom of your foot.
Plantar fasciitis develops from repetitive stress. Suddenly increasing your activity level, spending long hours standing on hard surfaces, wearing unsupportive shoes, or carrying extra body weight can all overload one foot more than the other. Subtle differences in how you walk, leg length discrepancies, or an old injury that changed your gait can explain why only one side is affected.
Heel Fat Pad Syndrome
Directly beneath your heel bone sits a specialized cushion of fat that absorbs shock with every step. When this pad thins out or loses its elasticity, you lose that natural shock absorber. Normal heel pad thickness is 1 to 2 centimeters. Below that, the heel bone is closer to the ground surface, and pain follows.
This condition is considered the second leading cause of heel pain after plantar fasciitis, and it’s frequently misdiagnosed as plantar fasciitis because the location is similar. The key difference is where the pain concentrates. Heel fat pad syndrome produces a deep, bruise-like pain right in the center of the heel, and you can reproduce it by pressing firmly into the middle of the pad. Plantar fasciitis pain tends to sit more toward the front-inside edge of the heel. Fat pad pain also gets significantly worse when walking barefoot on hard floors like concrete or tile, and during high-impact activities like jumping or running.
Stress Fracture of the Heel Bone
A stress fracture in the calcaneus (heel bone) is a small crack that develops gradually from repetitive loading rather than a single traumatic event. Unlike plantar fasciitis, which tends to feel worst with the first steps of the day, stress fracture pain builds over days to weeks and doesn’t improve with walking. It often gets steadily worse with any weight-bearing activity.
One reliable clue is the squeeze test: if someone gently squeezes the sides of your heel (not the bottom) and that reproduces your pain, a stress fracture is likely. Plantar fasciitis won’t typically hurt with side-to-side compression. Stress fractures are more common in runners, military recruits, people with low bone density, and anyone who ramps up physical activity too quickly. Because the pain can be vague and generalized across the entire heel, this diagnosis is sometimes missed on initial evaluation. X-rays can appear normal early on, so an MRI or CT scan may be needed if a fracture is suspected.
Nerve Entrapment
Nerves running through or near the heel can become compressed, producing pain that’s often burning, tingling, or electric in character. Two nerve-related causes are worth knowing about.
Tarsal Tunnel Syndrome
The tibial nerve passes through a narrow passage on the inner side of your ankle called the tarsal tunnel, formed by bones and ligaments. When this nerve gets compressed, you can feel pain, tingling, or numbness that radiates into the heel and bottom of the foot. It’s essentially the ankle’s version of carpal tunnel syndrome in the wrist. Swelling from an ankle sprain, flat feet, or a cyst near the tunnel can all trigger it. During an exam, your doctor may tap on the nerve at the inside of your ankle. If that reproduces your tingling or pain, it’s a strong indicator.
Baxter’s Nerve Entrapment
A smaller, less well-known nerve called the inferior calcaneal nerve (often called Baxter’s nerve) branches off near the tarsal tunnel and runs along the bottom of the foot, passing just in front of the heel bone. When it gets pinched, typically by tight surrounding muscles or a bone spur, it causes chronic heel pain that can closely mimic plantar fasciitis. Up to 20% of chronic heel pain cases are attributed to Baxter’s nerve entrapment. This is one of the main reasons people don’t improve with standard plantar fasciitis treatment. MRI can help with diagnosis by revealing changes in a small muscle on the outside of the foot that the nerve supplies.
Achilles Tendon Problems
The Achilles tendon connects your calf muscles to the back of your heel bone. When it becomes inflamed or develops small tears at or near its attachment point, the pain is felt at the back of the heel rather than the bottom. This is called insertional Achilles tendinopathy, and it’s distinct from plantar fasciitis in location: if you can point to the back of the heel where the tendon meets the bone, rather than the sole of the foot, the Achilles is more likely involved. Tight calf muscles, hill running, and footwear that digs into the back of the heel are common contributors.
Less Common Causes
When heel pain in one foot doesn’t respond to treatment or doesn’t fit the patterns above, other possibilities come into play. Lower back problems, particularly nerve compression at the L4 through S2 vertebral levels, can send pain down into the heel. This type of pain often comes with numbness or weakness in the foot or leg and may change with body position. Gout can strike the heel, producing sudden, intense pain with redness and swelling. Infections of the bone (osteomyelitis), especially in people with diabetes, and tumors are rare but worth ruling out in unusual presentations.
Inflammatory arthritis conditions like rheumatoid arthritis or ankylosing spondylitis can cause heel pain, but these tend to affect both feet and come with other joint symptoms. When pain is truly isolated to one heel with no other joint involvement, a mechanical cause is far more likely.
How Doctors Figure Out the Cause
The location and timing of your pain are the two most useful clues. Pain on the bottom of the heel that’s worst with your first morning steps points toward plantar fasciitis. Deep center-heel pain that worsens on hard surfaces suggests fat pad problems. Pain that came on gradually and hurts when the heel is squeezed from the sides raises concern for a stress fracture. Burning, tingling, or numbness suggests nerve involvement.
For imaging, weight-bearing X-rays are the standard starting point. They’re useful for ruling out fractures, bone spurs, and other bone abnormalities, though they won’t show soft tissue problems like early plantar fasciitis. If X-rays are normal and symptoms persist, ultrasound and MRI are the next steps. Ultrasound has about 80% sensitivity and 88% specificity for diagnosing plantar fasciitis, and it has the advantage of dynamic imaging, meaning your doctor can watch the tissues move in real time. MRI is considered the most sensitive overall and is particularly useful when nerve entrapment or a stress fracture is suspected.
Why Only One Foot?
The reason heel pain tends to hit one side comes down to asymmetry. Almost nobody walks, stands, or distributes weight perfectly evenly. Your dominant leg may absorb more force. A slight difference in arch height, foot flexibility, or leg length can concentrate stress on one heel. Previous injuries, even ones you’ve forgotten about, can change your movement patterns enough to overload one foot. If you’ve recently started a new sport, switched shoes, or changed your daily routine, the foot that bears more of the adjustment often pays the price first.
That said, if the pain in one foot persists beyond a few weeks of rest, ice, supportive footwear, and gentle calf stretching, it’s worth getting a proper evaluation. Conditions like nerve entrapment and stress fractures won’t resolve with the standard plantar fasciitis approach, and the sooner you identify the actual cause, the faster you’ll recover.