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

Identified risk factors for plantar fasciitis include excessive running, standing on hard surfaces for prolonged periods of time, high arches of the feet, the presence of a leg length inequality, and flat feet. The tendency of flat feet to excessively roll inward during walking or running makes them more susceptible to plantar fasciitis. Obesity is seen in 70% of individuals who present with plantar fasciitis and is an independent risk factor.

Studies have suggested a strong association exists between an increased body mass index and the development of plantar fasciitis in the non-athletic population; this association between weight and plantar fasciitis has not been observed in the athletic population. Achilles tendon tightness and inappropriate footwear have also been identified as significant risk factors.

Plantar fasciitis is the most common type of plantar fascia injury and is the most common reason for heel pain, responsible for 80% of cases. The condition tends to occur more often in women, military recruits, older athletes, the obese, and young male athletes.

Plantar fasciitis is estimated to affect 1 in 10 people at some point during their lifetime and most commonly affects people between 40–60 years of age. In the United States alone, more than two million people receive treatment for plantar fasciitis. The cost of treating plantar fasciitis in the United States is estimated to be $284 million each year.

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.

Bone mineral density decreases with increasing age. Osteoporotic bone loss can be prevented through an adequate intake of vitamin C and vitamin D, coupled with exercise and by being a non-smoker. A study by Cheng et al. in 1997, showed that greater bone density indicated less risk for fractures in the calcaneus.

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.

Calcaneal fractures are often attributed to shearing stress adjoined with compressive forces combined with a rotary direction (Soeur, 1975). These forces are typically linked to injuries in which an individual falls from a height, involvement in an automobile accident, or muscular stress where the resulting forces can lead to the trauma of fracture. Overlooked aspects of what can lead to a calcaneal fracture are the roles of osteoporosis and diabetes.

Unfortunately, the prevention of falls and automobile accidents is limited and applies to unique circumstances that should be avoided. The risk of muscular stress fractures can be reduced through stretching and weight-bearing exercise, such as strength training. In addition, footwear can influence forces that may cause a calcaneal fracture and can prevent them as well. A 2012 study conducted by Salzler showed that the increasing trend toward minimalist footwear or running barefoot can lead to a variety of stress fractures including that of the calcaneus.

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

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.

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.

More than 70% of cases are recorded in people with at least one of the following clinical situations: immunosuppression, diabetes, alcoholism/drug abuse/smoking, malignancies, and chronic systemic diseases. For reasons that are unclear, it occasionally occurs in people with an apparently normal general condition.

The infection begins locally at a site of trauma, which may be severe (such as the result of surgery), minor, or even non-apparent.

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 organisms include Group A "Streptococcus" (group A strep), "Klebsiella", "Clostridium", "Escherichia coli", "Staphylococcus aureus," and "Aeromonas hydrophila", and others. Group A strep is considered the most common cause of necrotizing fasciitis.

The majority of infections are caused by organisms that normally reside on the individual's skin. These skin flora exist as commensals and infections reflect their anatomical distribution (e.g. perineal infections being caused by anaerobes).

Sources of MRSA may include working at municipal waste water treatment plants, exposure to secondary waste water spray irrigation, exposure to run off from farm fields fertilized by human sewage sludge or septage, hospital settings, or sharing/using dirty needles. The risk of infection during regional anesthesia is considered to be very low, though reported.

Vibrio vulnificus, a bacterium found in saltwater, is a rare cause.

An accessory navicular bone is an accessory bone of the foot that occasionally develops abnormally in front of the ankle towards the inside of the foot. This bone may be present in approximately 2-21% of the general population and is usually asymptomatic. When it is symptomatic, surgery may be necessary.

Surgery can be performed at any age because it does not alter any other bones.

Symptoms of an accessory navicular bone may include plantar fasciitis, bunions and heel spurs.

Cellulitis in 2015 resulted in about 16,900 deaths worldwide, up from 12,600 in 2005.

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.

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.

Typical age of onset is around 40 to 50 years. It is not clear whether it is more common in women than men - patient numbers are small and some studies report a preponderance of men and others women. It is also found in children.

Heel pad syndrome, also known as heel fat pad syndrome, heel pad atrophy and heel fat pad atrophy, is a pain that occurs in the center of the heel. It is typically due to atrophy of the fat pad which makes up the heel. Risk factors include obesity. Other conditions with similar symptoms include plantar fasciitis. Treatment includes rest, pain medication, and heel cups. It becomes more common with age.

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 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.

Eosinophilic fasciitis (), also known as "Shulman's syndrome", is a form of fasciitis, the inflammatory diseases that affect the fascia, the connective tissues surrounding muscles, blood vessels and nerves. Unlike other diseases in that category, it is limited to the arms and legs, and usually resolves itself, although some cases require corticosteroids, and some cases are associated with aplastic anemia.

The presentation of eosinophilic fasciitis is similar to scleroderma or systemic sclerosis. However, unlike scleroderma, it affects the fascia, not the skin (dermis). The characteristic and severe effects of scleroderma and systemic sclerosis, such as Raynaud's syndrome, involvement of the extremities, prominent small blood vessels (telangiectasia), and visceral changes such as swallowing problems, are absent.

It was first characterized in 1974, and it is not yet known whether it is actually a distinct condition or just a different presentation. However, it remains used for diagnostic purposes.

Several cases have been reported after strenuous exercise.

Morton's Toe is a minority variant of foot shape. Its recorded prevalence varies in different populations, with estimates from 2.95% to 22%.

There are few good estimates of prevalence for pes cavus in the general community. While pes cavus has been reported in between 2 and 29% of the adult population, there are several limitations of the prevalence data reported in these studies. Population-based studies suggest the prevalence of the cavus foot is approximately 10%.

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%.