The differential diagnosis for heel pain is extensive and includes pathological entities including, but not limited to the following: calcaneal stress fracture, calcaneal bursitis, osteoarthritis, spinal stenosis involving the nerve roots of lumbar spinal nerve 5 (L5) or sacral spinal nerve 1 (S1), calcaneal fat pad syndrome, hypothyroidism, seronegative spondyloparthopathies such as reactive arthritis, ankylosing spondylitis, or rheumatoid arthritis (more likely if pain is present in both heels), plantar fascia rupture, and compression neuropathies such as tarsal tunnel syndrome or impingement of the medial calcaneal nerve.

A determination about a diagnosis of plantar fasciitis can usually be made based on a person's medical history and physical examination. In cases in which the physician suspects fracture, infection, or some other serious underlying condition, an x-ray may be used to make a differential diagnosis. However, and especially for people who stand or walk a lot at work, x-rays should not be used to screen for plantar fasciitis unless imaging is otherwise indicated as using it outside of medical guidelines is unnecessary health care.

Plantar fasciitis is usually diagnosed by a health care provider after consideration of a person's presenting history, risk factors, and clinical examination. Tenderness to palpation along the inner aspect of the heel bone on the sole of the foot may be elicited during the physical examination. The foot may have limited dorsiflexion due to tightness of the calf muscles or the Achilles tendon. Dorsiflexion of the foot may elicit the pain due to stretching of the plantar fascia with this motion. Diagnostic imaging studies are not usually needed to diagnose plantar fasciitis. However, in certain cases a physician may decide imaging studies (such as X-rays, diagnostic ultrasound or MRI) are warranted to rule out serious causes of foot pain.

Other diagnoses that are typically considered include fractures, tumors, or systemic disease if plantar fasciitis pain fails to respond appropriately to conservative medical treatments. Bilateral heel pain or heel pain in the context of a systemic illness may indicate a need for a more in-depth diagnostic investigation. Under these circumstances, diagnostic tests such as a CBC or serological markers of inflammation, infection, or autoimmune disease such as C-reactive protein, erythrocyte sedimentation rate, anti-nuclear antibodies, rheumatoid factor, HLA-B27, uric acid, or Lyme disease antibodies may also be obtained. Neurological deficits may prompt an investigation with electromyography to evaluate for damage to the nerves or muscles.

An incidental finding associated with this condition is a heel spur, a small bony calcification on the calcaneus (heel bone), which can be found in up to 50% of those with plantar fasciitis. In such cases, it is the underlying plantar fasciitis that produces the heel pain, and not the spur itself. The condition is responsible for the creation of the spur though the clinical significance of heel spurs in plantar fasciitis remains unclear.

In medicine, fasciitis is an inflammation of the fascia, which is the connective tissue surrounding muscles, blood vessels and nerves.

In particular, it often involves one of the following diseases:

- Necrotizing fasciitis

- Plantar fasciitis

- Eosinophilic fasciitis

- Paraneoplastic fasciitis

Early diagnosis is difficult as the disease often looks early on like a simple superficial skin infection. While a number of laboratory and imaging modalities can raise the suspicion for necrotizing fasciitis, the gold standard for diagnosis is a surgical exploration in the setting of high suspicion. When in doubt, a small "keyhole" incision can be made into the affected tissue, and if a finger easily separates the tissue along the fascial plane, the diagnosis is confirmed and an extensive debridement should be performed.

Computed tomography (CT scan) is able to detect approximately 80% of cases while MRI may pick up slightly more.

The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score can be utilized to risk stratify people having signs of cellulitis to determine the likelihood of necrotizing fasciitis being present. It uses six serologic measures: C-reactive protein, total white blood cell count, hemoglobin, sodium, creatinine and glucose. A score greater than or equal to 6 indicates that necrotizing fasciitis should be seriously considered. The scoring criteria are as follows:

- CRP (mg/L) ≥150: 4 points

- WBC count (×10/mm)

- <15: 0 points

- 15–25: 1 point

- >25: 2 points

- Hemoglobin (g/dL)

- >13.5: 0 points

- 11–13.5: 1 point

- <11: 2 points

- Sodium (mmol/L) <135: 2 points

- Creatinine (umol/L) >141: 2 points

- Glucose (mmol/L) >10: 1 point

As per the derivation study of the LRINEC score, a score of ≥6 is a reasonable cut-off to rule in necrotizing fasciitis, but a LRINEC <6 does not completely rule out the diagnosis. Diagnoses of severe cellulitis or abscess should also be considered due to similar presentations. 10% of patients with necrotizing fasciitis in the original study still had a LRINEC score <6. But a validation study showed that patients with a LRINEC score ≥6 have a higher rate of both mortality and amputation.

It is often seen as a repetitive stress injury, and thus lifestyle modification is typically the basic course of management strategies. For example, a person should begin doing foot and calf workouts. Strong muscles in the calves and lower legs will help take the stress off the bone and thus help cure or prevent heel spurs. Icing the area is an effective way to get immediate pain relief.

Conventional radiography is usually the initial assessment tool when a calcaneal fracture is suspected. Recommended x-ray views are (a) axial, (b) anteroposterior, (c) oblique and (d) views with dorsiflexion and internal rotation of the foot. However, conventional radiography is limited for visualization of calcaneal anatomy, especially at the subtalar joint. A CT scan is currently the imaging study of choice for evaluating calcaneal injury and has substituted conventional radiography in the classification of calcaneal fractures. Axial and coronal views are obtained for proper visualization of the calcaneus, subtalar, calcaneocuboid and talonavicular joints.

Manual therapy and exercise have better efficacy in the long term than electrophysical agents and exercise for function, but not for pain. Manual therapy and exercise are preferably focused at stretching the plantar fascia.

Other conditions that may mimic cellulitis include deep vein thrombosis, which can be diagnosed with a compression leg ultrasound, and stasis dermatitis, which is inflammation of the skin from poor blood flow. Signs of a more severe infection such as necrotizing fasciitis or gas gangrene that would require prompt surgical intervention include purple bullae, skin sloughing, subcutaneous edema, and systemic toxicity. Misdiagnosis can occur in up to 30% of people with suspected lower-extremity cellulitis, leading to 50,000 to 130,000 unnecessary hospitalization and $195 to $515 million in avoidable healthcare spending annually in the United States.

Associated musculoskeletal findings are sometimes reported. When it occurs with acne conglobata, hidradenitis suppurativa, and pilonidal cysts, the syndrome is referred to as the follicular occlusion triad or tetrad.

Lyme disease can be misdiagnosed as staphylococcal- or streptococcal-induced cellulitis. Because the characteristic bullseye rash does not always appear in people infected with Lyme disease, the similar set of symptoms may be misdiagnosed as cellulitis. Standard treatments for cellulitis are not sufficient for curing Lyme disease. The only way to rule out Lyme disease is with a blood test, which is recommended during warm months in areas where the disease is endemic.

Aside from surgery, there are a few options for handling an accessory navicular bone that has become symptomatic. This includes immobilization, icing, medicating, physical therapy, and orthotic devices. Immobilizing involves placing the foot and ankle in a cast or removable walking boot. This alleviates stressors on the foot and can decrease inflammation. Icing will help reduce swelling and inflammation. Medication involves usage of nonsteroidal anti-inflammatory drugs, or steroids (taken orally or injected) to decrease inflammation. Physical therapy can be prescribed in order to strengthen the muscles and help decrease inflammation. Physical therapy can also help prevent the symptoms from returning. Orthotic devices (arch support devices that fit in a shoe) can help prevent future symptoms. Occasionally, the orthotic device will dig into the edge of the accessory navicular and cause discomfort. For this reason, the orthotic devices made for the patient should be carefully constructed.

In those who have previously had cellulitis, the use of antibiotics may help prevent future episodes. This is recommended by CREST for those who have had more than two episodes.

Evaluating soft-tissue involvement is the most important aspect of the clinical examination because of its association with patient outcome. Skin blisters may become infected if medical attention is delayed, which can lead to necrotizing fasciitis or osteomyelitis, causing permanent damage to muscle or bone. Ligament and tendon involvement should also be explored. Achilles tendon injury can be seen with posterior (Type C) fractures. Since calcaneal fractures are related to falls from height, other concomitant injuries should be evaluated. Vertebral compression fractures occur in approximately 10% of these patients. A trauma-focused clinical approach should be implemented; tibial, knee, femur, hip, and head injuries should be ruled out by means of history and physical exam.

Plantar calcaneal bursitis is a medical condition in which there is inflammation of the plantar calcaneal bursa, a spongy fluid filled sac that cushions the fascia of the heel and the calcaneus (heel bone). It is characterized by swelling and tenderness of the central plantar heel area. It is sometimes called 'Policeman's heel'. It sometimes was, and should not be, confused with plantar fasciitis, which is inflammation of the plantar fascia and can affect any part of the foot.

Plantar fasciitis is a common cause of calcaneal spurs. To quote Edward Kwame Agyekum, "When stress is put on the plantar fascia ligament, it does not cause only plantar fasciitis, but cause[s] a heel spur... where the plantar fascia attaches to the heel bone. Generally, a calcaneal spur develops when proper care is not given to the foot and heels. People who are obese, have flat feet, or who often wear high-heeled shoes are most susceptible to heel spurs.

The key to diagnosis is skin changes combined with blood eosinophilia but the most accurate test is a skin, fascia and muscle biopsy.

In medicine, an enthesopathy refers to a disorder involving the attachment of a tendon or ligament to a bone. This site of attachment is known as the entheses.

If the condition is known to be inflammatory, it can more precisely be called an enthesitis.

The main differential diagnosis of heel pad syndrome is plantar fasciitis. In heel pad syndrome all parts of the heel are tender while in plantar fasciitis typically only the part of the heel closer to the toes is sore.

While recent case series (n=9-80) studies have found a mortality rate of 20-40%, a large (n=1641) 2009 study reported a mortality rate of 7.5%.

The Geist classification divides the accessory navicular bones into three types.

- Type 1: An os tibiale externum is a 2–3 mm sesamoid bone in the distal posterior tibialis tendon. Usually asymptomatic.

- Type 2: Triangular or heart-shaped ossicle measuring up to 12 mm, which represents a secondary ossification center connected to the navicular tuberosity by a 1–2 mm layer of fibrocartilage or hyaline cartilage. Portions of the posterior tibialis tendon sometimes insert onto the accessory ossicle, which can cause dysfunction, and therefore, symptoms.

- Type 3: A cornuate navicular bone represents an enlarged navicular tuberosity, which may represent a fused Type 2 accessory bone. Occasionally symptomatic due to bunion formation.

In some cases, foot diseases and painful conditions can be treated. Synovium hydrates the cartilage in the heal and can bring pain relief quickly. Synovium gel looks as well as strongly smells like urine, straying some consumers away. However this only occurs after expiration. Blood thinners can also work however are deemed as bad relievers by medical practitioners due to the fact that they can contribute to headaches and in some cases increase foot pain afterwards.

Enthesopathies may take the form of spondyloarthropathies (joint diseases of the spine) such as ankylosing spondylitis, plantar fasciitis, and Achilles tendinitis. Enthesopathy can occur at the elbow, wrist, carpus, hip, knee, ankle, tarsus, or heel bone, among other regions. Further examples include:

- Adhesive capsulitis of shoulder

- Rotator cuff syndrome of shoulder and allied disorders

- Periarthritis of shoulder

- Scapulohumeral fibrositis

- Synovitis of hand or wrist

- Periarthritis of wrist

- Gluteal tendinitis

- Iliac crest spur

- Psoas tendinitis

- Trochanteric tendinitis

Fournier gangrene is usually diagnosed clinically, but laboratory tests and imaging studies are used to confirm diagnosis, determine severity and predict outcomes. X-rays and ultrasounds may show the presence of gas below the surface of the skin. A CT scan can be useful in determining the site of origin and extent of spread.

Atherosclerotic restriction to the arterial supply in peripheral artery occlusive disease may result in painful arterial ulcers of the ankle and foot, or give rise of gangrene of the toes and foot. Immobility of a person may result in prolonged pressure applied to the heels causing pressure sores.

Impaired venous drainage from the foot in varicose veins may sequentially result in brown haemosiderin discolouration to the ankle and foot, varicose stasis dermatitis and finally venous ulcers.

Other disorders of the foot include osteoarthritis of the joints, peripheral neuropathy and plantar warts.

Common treatments include corticosteroids such as prednisone, though other medications such as hydroxychloroquine have also been used.

The prognosis is usually good in the case of an early treatment if there is no visceral involvement.

Asymptomatic anatomical variations in feet generally do not need treatment.

Conservative treatment for foot pain with Morton's toe may involve exercises or placing a flexible pad under the first toe and metatarsal; an early version of the latter treatment was once patented by Dudley Joy Morton. Restoring the Morton’s toe to normal function with proprioceptive orthotics can help alleviate numerous problems of the feet such as metatarsalgia, hammer toes, bunions, Morton's neuroma, plantar fasciitis, and general fatigue of the feet. Rare cases of disabling pain are sometimes treated surgically.