Pain along the inner or outer edge of your heel usually points to a different set of problems than the classic “bottom of the heel” ache most people associate with plantar fasciitis. The sides of the heel are home to tendons, nerves, and bony landmarks that each have their own ways of going wrong, and whether the pain is on the lateral (outer) side or medial (inner) side narrows the list of suspects considerably. Getting the location right matters because the treatments diverge just as sharply as the causes.
Lateral Heel Pain
When pain parks itself along the outer edge of your heel or just below the outer ankle bone, three culprits show up most often: peroneal tendon problems, sinus tarsi syndrome, and sural nerve irritation.
The peroneal tendons run behind the outer ankle bone and attach near the base of the foot. They help stabilize the ankle during walking and running, and they are frequently overlooked when someone complains of lateral hindfoot pain. Peroneal tendon disorders include tendonitis, tears, and subluxation, where the tendon slips out of its groove behind the ankle bone.1PubMed. Pathologies of the Peroneals: A Review If you have had ankle sprains in the past, the risk goes up because the stabilizing structures around those tendons may have been stretched or torn. The pain tends to worsen with activity, especially side-to-side movements or walking on uneven ground.
Sinus tarsi syndrome is a less familiar name but a common enough problem. The sinus tarsi is a small, tunnel-like space on the outer side of the foot just in front of the ankle joint. Excessive motion in the subtalar joint, often after an ankle sprain or in people with very flat feet, can lead to inflammation and scar tissue filling that space.2PubMed Central. Examination and intervention for sinus tarsi syndrome People with sinus tarsi syndrome typically describe pain right over the outer opening of the space and a vague feeling that the ankle might give way.3PubMed. The sinus tarsi syndrome The instability component is what often separates it from a straightforward tendon issue.
The sural nerve runs along the back and outer side of the lower leg and foot. Compression or direct trauma to this nerve can cause burning pain, heightened skin sensitivity, and sharp sensations localized to the outer heel and ankle region.4PubMed Central. Overview of nerve entrapment syndromes in the foot and ankle Prior ankle surgery, tight-fitting boots, or even a scar from an old injury can all set off sural nerve symptoms. The character of the pain is a clue: burning, tingling, or electric-shock sensations point toward a nerve problem rather than a tendon or joint issue.
Medial Heel Pain
Pain on the inner side of the heel has its own set of causes, and they often overlap in ways that make diagnosis tricky.
Posterior tibial tendon dysfunction is the most common cause of adult-acquired flatfoot and a frequent source of medial heel and arch pain. The posterior tibial tendon runs behind the inner ankle bone and supports the arch of the foot. When it degenerates, the arch gradually collapses, and the foot rolls inward more than it should. Early on, you notice pain and tenderness along the inside of the ankle and heel; later, the foot visibly changes shape.5PubMed Central. Posterior tibial tendon dysfunction: an overlooked cause of foot deformity This condition tends to progress if left untreated, moving from a painful but structurally normal foot to one with permanent deformity and joint damage.6PubMed Central. Posterior Tibial Tendon Dysfunction: An Overview
Tarsal tunnel syndrome is essentially the foot’s version of carpal tunnel syndrome. The tarsal tunnel sits just behind the inner ankle bone, and the posterior tibial nerve passes through it. When that nerve gets compressed, you feel numbness, tingling, and burning pain in the heel and sole.7PubMed Central. Tarsal Tunnel Syndrome – A Comprehensive Review Runners are particularly susceptible because repetitive impact and foot pronation can swell the tissues around the tunnel.8PubMed. Tarsal tunnel syndrome in runners The numbness and burning distinguish tarsal tunnel from a purely mechanical tendon problem, though the two can coexist in the same foot.
Interestingly, researchers have identified a “heel pain triad” in which plantar fasciitis, posterior tibial tendon dysfunction, and tarsal tunnel syndrome all occur together. The theory is that when both the plantar fascia and the posterior tibial tendon fail, the arch collapses enough to pull on the tibial nerve, creating tarsal tunnel symptoms on top of everything else.9PubMed. Heel pain triad (HPT): the combination of plantar fasciitis, posterior tibial tendon dysfunction and tarsal tunnel syndrome If you have inner heel pain that does not respond to typical plantar fasciitis treatment, there may be more than one thing going on.
Baxter’s Nerve Entrapment
Baxter’s nerve entrapment deserves its own mention because it is so frequently misdiagnosed. Baxter’s nerve is the first branch of the lateral plantar nerve, and it gets pinched between structures deep in the heel. The result is chronic, burning pain on the inner-to-bottom aspect of the heel that mimics plantar fasciitis almost perfectly. Because imaging does not always reveal the problem and the pain location overlaps with plantar fasciitis, many people go through rounds of stretching, orthotics, and steroid injections without relief before anyone considers the nerve.10PubMed. Baxter’s nerve: the hidden culprit of chronic heel pain The presence of neurological symptoms like tingling, burning, or altered sensation is the strongest clue that a nerve is involved rather than the fascia alone.
Calcaneal Stress Fractures
A stress fracture of the heel bone can cause pain that feels deep, vague, and hard to localize, which is part of the reason these fractures get missed. The calcaneus bears a huge share of your body weight with every step, and repetitive loading can crack it without a dramatic injury. Initial X-rays frequently look normal, and many people are told they have a soft tissue injury. A case report illustrating the problem involved a 57-year-old woman whose X-rays showed nothing after a minor trauma, but persistent pain eventually led to an MRI that revealed the fracture.11PubMed Central. Delayed Diagnosis of Calcaneal Stress Fracture: A Case Report If squeezing the sides of your heel reproduces the pain, and the pain worsens with weight-bearing activity but does not improve with typical soft-tissue treatments, push for advanced imaging.
People most at risk include runners who have recently ramped up mileage, military recruits, and anyone with low bone density. The squeeze test, where someone compresses the heel from both sides at once, is a quick screening tool that clinicians use to suspect a calcaneal fracture before ordering an MRI.
How Foot Mechanics and Pronation Contribute
The way your foot moves during walking and running can load the sides of your heel unevenly. Pronation, the inward rolling of the foot as it strikes the ground, is a normal part of the gait cycle, but excessive pronation increases strain on medial structures like the posterior tibial tendon and the tibial nerve. Data from the Framingham Foot Study found that pronated foot function was associated with roughly a 50 percent higher likelihood of heel pain in men.12Arthritis Care & Research. Association of planus foot posture and pronated foot function with foot pain: the Framingham foot study Women with a more supinated, or outward-rolling, foot function actually had some protection against hindfoot pain in the same study.
What this means practically is that foot type is not destiny, but it does shift the odds. If you overpronate, the inner side of your heel is doing more work than it was designed for, and the structures there fatigue faster. If you supinate heavily, the outer side takes the extra load, potentially setting up peroneal tendon strain or sinus tarsi irritation. Neither pattern guarantees problems, but both create a vulnerability that training errors, weight gain, or worn-out shoes can exploit.
Footwear and Running Surfaces
Shoes that fit poorly or lack adequate structure around the heel can contribute to side-of-heel pain. A review on everyday footwear found that shoes impeding normal foot function cause altered gait patterns that contribute to foot problems, whether because the shoe is too loose and allows excessive sliding or too tight and concentrates pressure.13The Foot. Everyday footwear: An overview of what we know and what we should know on ill-fitting footwear and associated pain and pathology If the heel counter of your shoe is soft or broken down, the back of the shoe cannot stabilize your heel during ground contact, and both sides absorb forces they would normally share more evenly.
Running on sloped or cambered surfaces is another underappreciated factor. Roads are typically crowned, meaning runners who always face traffic end up with one foot on a slight uphill and the other on a slight downhill. Research on side-sloped running found that the uphill foot showed greater eversion and external rotation, meaning it rolled inward more than the downhill foot.14Sports Biomechanics. Side-sloped surfaces substantially affect lower limb running kinematics Run the same route in the same direction every day, and one heel is chronically overpronating while the other is chronically underpronating. Alternating sides of the road or seeking flat paths is a simple fix that runners often overlook.
When Heel Pain Signals a Systemic Condition
Not all heel pain starts and ends in the foot. The spondyloarthropathies, a group of inflammatory diseases that includes ankylosing spondylitis and psoriatic arthritis, have a particular fondness for the spots where tendons and ligaments attach to bone. This type of inflammation, called enthesitis, frequently targets the Achilles tendon insertion and the plantar fascia origin at the heel, often on both sides and with a tendency to recur.15PubMed Central. Review: Enthesitis: New Insights Into Pathogenesis, Diagnostic Modalities, and Treatment If your heel pain is bilateral, keeps coming back, and you also have morning stiffness in your back or swollen fingers or toes, it is worth mentioning these symptoms to your doctor. A purely mechanical problem in the heel usually stays on one side and responds to rest; inflammatory enthesitis follows a different pattern.
Imaging can help but is not definitive. A study comparing MRI and ultrasound in people with spondyloarthritis found that painful heels had inflammatory changes about 80 percent of the time on MRI, but controls also showed abnormalities on imaging, so neither MRI nor ultrasound could reliably diagnose the underlying disease by looking at the heel alone.16Annals of the Rheumatic Diseases. Comparative study of MRI and power Doppler ultrasonography of the heel in patients with spondyloarthritis with and without heel pain and in controls The imaging is useful for tracking inflammation once you have the diagnosis, but it cannot replace clinical evaluation.
Sever’s Disease in Children and Adolescents
If your child or teenager complains about pain on both sides of the heel, especially during or after sports, the likely culprit is Sever’s disease. This is not actually a disease but an overuse condition of the growth plate at the back of the heel bone. During growth spurts, the growth plate is softer and more vulnerable to repetitive traction from the Achilles tendon. Physical examination typically shows tenderness with compression at the medial and lateral sides of the heel.17Advanced Emergency Nursing Journal. Sever’s Disease (Calcaneal Apophysitis) It is self-limiting and resolves when the growth plate fuses, usually by the mid-teens, but activity modification, heel cushions, and stretching help manage pain in the meantime.
Getting the Right Diagnosis
Because so many conditions can produce heel pain, diagnosis starts with pinpointing exactly where it hurts and what makes it worse. The most common cause of heel pain overall in adults is plantar fasciitis, which typically produces pain with the first steps in the morning or after sitting for a long time, centered at the bottom of the heel where the plantar fascia attaches.18PubMed. Diagnosing heel pain in adults Side-of-heel pain departs from that classic pattern, and the distinction matters. Knowing the anatomic location helps narrow the differential considerably: lateral pain points toward peroneal tendons, sinus tarsi, or sural nerve issues, while medial pain suggests posterior tibial tendon problems, tarsal tunnel syndrome, or Baxter’s nerve entrapment.19Ultrasonography. A problem-based approach in musculoskeletal ultrasonography: heel pain in adults
Ultrasound is increasingly used as a first-line imaging tool for heel pain. A comparative study found that ultrasound combined with shear wave elastography could identify plantar fasciitis with about 93 percent accuracy and Achilles tendinopathy with about 98 percent accuracy, correlating well with MRI findings.20PubMed Central. Ultrasound imaging and shear wave elastography for the differential diagnosis of heel pain: a comparative cross-sectional study Ultrasound has the advantage of being quick, inexpensive, and available in many clinics without a referral. MRI remains the gold standard when a stress fracture is suspected or when ultrasound findings are inconclusive.
Conservative Approaches That Help
Most causes of side-of-heel pain respond to conservative treatment if you stick with it long enough. The specifics depend on the diagnosis, but several strategies apply broadly:
- Orthotic inserts: Wedged or custom foot orthoses can correct excessive pronation or supination and redistribute pressure away from the painful side. A randomized trial in runners with pronated feet found that wedged foot orthoses cut pain intensity roughly in half within two weeks, with about 60 percent of the treatment group becoming pain-free during testing.21PubMed. Application of wedged foot orthosis effectively reduces pain in runners with pronated foot: a randomized clinical study
- Stretching and strengthening: Calf stretches, eccentric heel drops for Achilles and peroneal tendon issues, and intrinsic foot muscle exercises all reduce the mechanical load on the heel. Consistency matters more than intensity.
- Activity modification: Reducing mileage, switching to lower-impact activities temporarily, or changing running surfaces can allow irritated tissues to recover. If you always run the same cambered road, alternating directions or moving to a track removes a subtle but real asymmetric load.
- Ice and anti-inflammatory medication: Standard short-term relief tools. Ice for ten to fifteen minutes after activity and over-the-counter anti-inflammatories can take the edge off while other treatments address the root cause.
- Shoe evaluation: Replacing worn-out shoes, choosing models with a firm heel counter, and making sure the shoe fits the width of your foot are low-cost interventions that remove a contributing factor.
For nerve-related pain like tarsal tunnel syndrome or sural nerve entrapment, the approach shifts slightly. Reducing compression is the priority, which may mean avoiding tight footwear, using padding around the ankle, or wearing a brace that limits excessive motion. Nerve symptoms that do not improve with conservative measures within a few months usually warrant a referral to a specialist.
Injections and Platelet-Rich Plasma
When conservative treatment stalls, corticosteroid injections are a common next step, particularly for plantar fasciitis and certain forms of enthesitis. They provide rapid pain relief by dampening inflammation, but the effect tends to be temporary, and repeated steroid injections carry risks including fat pad atrophy and weakening of the plantar fascia.
Platelet-rich plasma injections have gained traction as an alternative. Several randomized trials have compared PRP to corticosteroids for plantar fasciitis, and the results generally show that both provide meaningful relief. One trial found PRP to be more effective than steroid injection specifically for plantar fasciitis, while being safer for patients who cannot tolerate steroids, such as people with diabetes.22The Egyptian Rheumatologist. Local injection of autologous platelet rich plasma and corticosteroid in treatment of lateral epicondylitis and plantar fasciitis: Randomized clinical trial Other trials have found the two approaches equally effective.23PubMed. Comparison of Plantar Fasciitis Injected With Platelet-Rich Plasma vs Corticosteroids 24PubMed. The comparison of the effect of corticosteroids and platelet-rich plasma (PRP) for the treatment of plantar fasciitis The advantage of PRP, when it works, is that it avoids the tissue-weakening side effects of steroids. The disadvantage is cost and limited insurance coverage.
When Surgery Becomes an Option
Surgery for side-of-heel pain is uncommon and generally reserved for cases that have failed at least six to twelve months of conservative care. The type of surgery depends entirely on what is causing the pain. For chronic plantar fasciitis with suspected Baxter’s nerve involvement, one approach involves decompressing the nerve and performing a partial release of the plantar fascia, sometimes with drilling of the calcaneus to stimulate healing. In one surgical series, 80 percent of patients had no functional limitations six months after surgery, and nine out of ten reported satisfaction with the outcome.25Current Orthopaedic Practice. Chronic Heel Pain: When Is Surgery Indicated?
For peroneal tendon tears or chronic subluxation that does not respond to bracing, surgical repair or groove-deepening procedures can stabilize the tendons. Tarsal tunnel release, in which the ligament forming the roof of the tarsal tunnel is cut to free the compressed nerve, is an option for tarsal tunnel syndrome, though outcomes are less predictable than for its wrist counterpart. The evidence here is thinner and more variable, so surgery for tarsal tunnel syndrome is typically a last resort after thorough diagnostic workup confirms the nerve is genuinely compressed.
Posterior tibial tendon reconstruction is a bigger undertaking, sometimes involving tendon transfer and bone realignment procedures to restore the arch. If the tendon has deteriorated significantly and the foot has already deformed, conservative management can only do so much, and surgery aims to prevent further joint damage. Recovery from these procedures is measured in months, not weeks, with extended periods of non-weight-bearing and physical therapy.