Pain on the sides of your heels usually comes from irritated tendons, compressed nerves, or inflammation of the thick band of tissue along the bottom of your foot pulling at its attachment point. The specific location, whether inner or outer side, and the type of pain you feel (aching, burning, or sharp) narrow down the likely cause considerably.
Inner Heel Pain: The Most Common Side
The inner (medial) side of the heel is where most people feel side-heel pain, and plantar fasciitis is the leading cause. The plantar fascia is a thick band of tissue running from your heel bone to your toes, and it attaches at a bony bump on the inner-bottom edge of the heel called the medial calcaneal tuberosity. When this tissue becomes inflamed or develops small tears, you feel a throbbing pain right at that attachment point. The hallmark pattern is sharp pain with your first steps in the morning or after sitting for a while, pain that fades as you keep walking, then returns again after prolonged time on your feet.
But plantar fasciitis isn’t the only thing happening on the inner heel. Several tendons pass behind and around the inner ankle bone on their way to the foot, and any of them can become inflamed. The posterior tibialis tendon, which helps support your arch, causes tenderness along the inner side of the foot near the heel and midfoot. Tendons that control your toes also run through this area, and irritation of these produces pain that traces a line from behind the inner ankle bone down into the sole.
Nerve Compression on the Inner Side
If your pain includes tingling, burning, numbness, or a shooting sensation, a nerve may be involved. Tarsal tunnel syndrome is caused by compression of a major nerve that passes through a narrow channel behind the inner ankle bone. The pain and tingling can spread into the heel, sole, and toes, and it typically worsens at night or after prolonged standing. Some people also feel the discomfort radiating up into the calf.
A related but more specific problem involves a small nerve branch sometimes called Baxter’s nerve, which peels off from the main nerve inside the tarsal tunnel and runs right along the inner heel before turning toward the outer edge of the foot. When this nerve gets pinched, often from a pronated (flat or inward-rolling) foot or a bone spur, the pain mimics plantar fasciitis so closely that it’s frequently misdiagnosed. The key difference is that nerve pain tends to burn or tingle rather than produce the classic stabbing sensation of plantar fasciitis, and it doesn’t always follow the “worst in the morning” pattern.
Outer Heel Pain: Peroneal Tendon Problems
Pain on the outer (lateral) side of the heel most often involves the peroneal tendons, two tendons that run behind the outer ankle bone and along the side of the foot. These tendons help stabilize the ankle and turn the foot outward. Peroneal tendonitis causes intense pain along the outside of the foot and ankle, and it develops either gradually from repetitive overuse, like running on uneven surfaces or a sudden increase in training, or suddenly after an ankle sprain or fall.
The pain from peroneal tendon problems typically worsens with activity and improves with rest. You might notice swelling or warmth along the outer ankle, and turning your foot outward against resistance will reproduce the pain. This is particularly common in runners, hikers, and people who’ve had previous ankle sprains that left the outer ankle structures weakened.
Causes That Affect Both Sides
Some conditions don’t favor one side over the other. Fat pad atrophy, where the cushioning layer under your heel bone thins out, produces a deep bruise-like pain that can radiate to either side of the heel. A normal heel pad is 1 to 2 centimeters thick, and when it thins or loses elasticity, the heel bone sits closer to the ground with less shock absorption. This pain is worst when walking barefoot on hard floors, during high-impact activities like running or jumping, and after long periods of standing. You can sometimes feel the difference yourself: if pressing firmly into the center or sides of your heel feels like you’re pushing straight into bone rather than into a cushion, the fat pad may be the issue.
Heel spurs, small bony growths on the heel bone, get blamed frequently but are often incidental findings. Many people have heel spurs on X-rays with no pain at all. When a spur does contribute to symptoms, it’s usually because it’s pressing on nearby soft tissue or a nerve (like Baxter’s nerve) rather than because the spur itself is painful.
Less commonly, inflammatory conditions like rheumatoid arthritis, psoriatic arthritis, or reactive arthritis can cause heel pain, sometimes on both sides simultaneously. These systemic conditions usually come with other symptoms: joint pain and stiffness elsewhere in the body, morning stiffness lasting more than 30 minutes, or skin changes in the case of psoriatic arthritis. Heel pain that appears in both feet at the same time, especially alongside back stiffness in a younger adult, can be an early sign of ankylosing spondylitis.
How to Tell What’s Causing Yours
The location and character of the pain are your best clues:
- Sharp, stabbing pain on the inner heel that’s worst with first morning steps points toward plantar fasciitis.
- Burning, tingling, or numbness on the inner side suggests nerve compression, either tarsal tunnel syndrome or Baxter’s nerve entrapment.
- Pain along the outer ankle and heel that worsens with activity fits peroneal tendonitis.
- Deep, bruise-like pain on either side that’s worst on hard surfaces suggests fat pad thinning.
- Aching on the inner heel with a noticeably flat arch may involve the posterior tibialis tendon.
Pay attention to what makes the pain better or worse. Pain that eases as you warm up but returns with extended activity is typical of tendon problems and plantar fasciitis. Pain that builds steadily the longer you stand and includes tingling or numbness leans toward nerve compression. Pain that’s directly related to impact and surface hardness suggests a fat pad issue.
Recovery Timelines and What Helps
Most side-heel pain responds to conservative treatment, but the timeline varies depending on severity. Mild cases of plantar fasciitis typically improve within 6 to 8 weeks with rest, icing, and consistent stretching. Moderate to severe cases often take 3 to 6 months and may need supportive insoles or orthotics to correct foot alignment. Chronic cases that have lingered for over a year can take 6 to 12 months to fully resolve.
For peroneal tendonitis, acute flare-ups generally settle within 2 to 6 weeks if you reduce the activity that caused them. Chronic cases need 3 to 6 months of dedicated treatment including strengthening exercises for the outer ankle muscles.
Across most of these conditions, the general recovery arc looks similar: you can expect reduced morning pain within the first two weeks of treatment, noticeable improvement during daily activities by weeks 3 to 6, a return to higher activity levels around weeks 6 to 12, and full resolution between 3 and 6 months. The biggest factor in recovery speed is how early you address it. Pain that’s been building for months takes longer to resolve than pain you catch in the first few weeks.
Stretching the calf muscles and the plantar fascia, wearing shoes with adequate arch support and cushioning, avoiding prolonged barefoot walking on hard surfaces, and gradually increasing activity rather than pushing through pain are effective starting points for nearly all causes of side-heel pain. If the pain includes nerve symptoms like tingling or numbness, or if it hasn’t improved after 6 to 8 weeks of home treatment, imaging or nerve testing can help pinpoint the exact structure involved.