This comprehensive podiatric glossary defines over 100 foot and ankle medical terms used by podiatrists, physical therapists, insurance companies, and patients. Each term includes a plain-English definition written by Dr. Tom Biernacki DPM, board-certified podiatric surgeon at Balance Foot & Ankle in Michigan. Where applicable, each term links to the relevant condition or treatment page for more detailed information.

Jump to letter: A | B | C | D | E | F | G | H | I | L | M | N | O | P | R | S | T | U | V | W | X | Y

A

Achilles Tendon

The largest tendon in the body, connecting the calf muscles to the heel bone (calcaneus). The Achilles tendon enables plantarflexion — pushing the foot downward during walking, running, and jumping. It is susceptible to tendinopathy, rupture, and insertional disorders in active and sedentary patients alike.

Ankle Arthritis

Deterioration of cartilage within the tibiotalar (ankle) joint, causing pain, stiffness, and reduced range of motion. Most ankle arthritis is post-traumatic, developing years after ankle fractures or ligament injuries. Treatment ranges from custom orthotics and injections to ankle fusion or total ankle replacement.

Ankle Sprain

A stretching or tearing of one or more ankle ligaments, most commonly the anterior talofibular ligament (ATFL) on the lateral side. Graded I–III by severity. Proper rehabilitation is essential to prevent chronic ankle instability.

Arthrodesis

Surgical fusion of two bones across a joint, eliminating joint motion to relieve arthritis pain. Common sites include the ankle (tibiotalar), subtalar, midfoot (tarsometatarsal), and toe (interphalangeal) joints. Used when joint replacement is not appropriate.

Arthroplasty

Joint replacement surgery in which damaged articular surfaces are replaced with prosthetic components. In the foot and ankle, total ankle arthroplasty (TAR) is the primary arthroplasty procedure, preserving ankle motion while relieving arthritis pain.

Athlete’s Foot (Tinea Pedis)

A fungal skin infection of the foot caused by dermatophytes, most commonly Trichophyton rubrum. Presents as interdigital maceration, plantar scaling, or vesicles. Treated with topical antifungals; oral therapy for extensive or resistant cases.

Avulsion Fracture

A fracture in which a small fragment of bone is pulled away from its main body by an attached tendon or ligament. Common in the foot at the base of the fifth metatarsal (peroneus brevis avulsion) and the ankle during sprains.

B

Bunion (Hallux Valgus)

A progressive structural deformity at the first metatarsophalangeal (MTP) joint in which the big toe drifts toward the second toe and the first metatarsal head displaces medially. Causes a prominent bony bump, pain, and difficulty with footwear. Treated conservatively with orthotics and footwear modification, or surgically with an osteotomy (bone realignment).

Bursitis

Inflammation of a bursa — a fluid-filled sac that cushions between tendons, bones, and skin. In the foot, common bursitis locations include the retrocalcaneal bursa (behind the heel), the plantar heel bursa, and between the metatarsal heads (intermetatarsal bursitis).

C

Calcaneus

The heel bone — the largest bone in the foot. The calcaneus bears the brunt of impact loading during walking and running. Common pathologies include plantar fasciitis at its inferior attachment, Achilles tendinopathy at its posterior insertion, and calcaneal fractures from high-energy falls.

Callus (Tyloma)

A diffuse, flat area of thickened hyperkeratotic skin that develops over bony prominences in response to repeated friction or pressure. Unlike a corn (heloma), a callus lacks a discrete central core. Managed with professional debridement and pressure redistribution via orthotics or padding.

Charcot Arthropathy (Charcot Foot)

A progressive destructive arthropathy affecting the bones and joints of the foot and ankle in patients with peripheral neuropathy, most commonly from diabetes. Characterized by painless fractures, dislocations, and collapse of the midfoot or hindfoot. Requires urgent off-loading to prevent severe deformity.

Claw Toe

A toe deformity involving hyperextension at the metatarsophalangeal (MTP) joint and flexion at both interphalangeal (IP) joints, causing a claw-like appearance. Associated with neuromuscular imbalance, peripheral neuropathy, and compartment syndrome. More severe than hammertoe deformity.

Corn (Heloma)

A well-defined, conical hyperkeratotic lesion with a central core that points inward. Hard corns (heloma durum) form on bony prominences over the toes; soft corns (heloma molle) form in the moist web spaces. The core creates point pressure that is exquisitely painful. Treated with professional enucleation and addressing the underlying bony prominence.

Custom Orthotics

Prescription medical devices fabricated from a 3D model of an individual’s foot to modify force distribution and correct biomechanical abnormalities during gait. Functional orthotics control motion (rigid materials); accommodative orthotics cushion and offload pressure (soft materials). Covered by many Michigan insurance plans when medically necessary.

D

Diabetic Foot

A spectrum of foot complications occurring in people with diabetes mellitus, including peripheral neuropathy (nerve damage), peripheral arterial disease (poor circulation), skin and soft tissue infections, and diabetic foot ulcers. Preventive podiatric care is essential to reduce amputation risk.

Diabetic Foot Ulcer

A full-thickness skin wound on the plantar surface of the foot occurring in patients with diabetes, caused by repetitive pressure on insensate skin over a bony prominence. Classified by depth and infection status using the Wagner or University of Texas grading systems. Treatment involves off-loading, debridement, infection control, and wound care.

DPM (Doctor of Podiatric Medicine)

The professional degree earned by licensed podiatrists after completing a 4-year podiatric medical school program followed by a 3-year surgical residency. Podiatrists are licensed to diagnose and treat all conditions of the foot, ankle, and related lower extremity structures, including performing surgery.

DVT (Deep Vein Thrombosis)

A blood clot forming within a deep vein of the calf or leg, causing unilateral swelling, calf pain, and redness. DVT can dislodge and cause pulmonary embolism — a potentially fatal complication. Unilateral foot and ankle swelling with calf tenderness after surgery or immobility requires urgent vascular ultrasound evaluation.

E

Equinus Deformity

Limitation in ankle dorsiflexion (upward foot movement) due to tightness of the gastrocnemius muscle, Achilles tendon, or ankle joint capsule. Equinus forces compensatory pronation, contributing to plantar fasciitis, metatarsalgia, and Achilles tendinopathy. Treated with stretching, orthotics, or surgical gastrocnemius recession.

ESWT (Extracorporeal Shockwave Therapy)

A non-invasive treatment modality that delivers acoustic energy to chronically injured tissue, triggering a healing response via increased vascularity and growth factor release. FDA-approved for plantar fasciitis. Also used for insertional Achilles tendinopathy, calcific tendinitis, and stress fractures. Typically 3–5 sessions, outpatient.

F

Flat Foot (Pes Planus)

An abnormally low or absent medial longitudinal arch. Flexible flat feet are present only during weight bearing; rigid flat feet persist with the foot non-weight-bearing. Adult acquired flatfoot deformity (AAFD) develops from posterior tibial tendon dysfunction and is the most clinically significant flatfoot variant in adults.

FHL (Flexor Hallucis Longus)

A muscle of the posterior calf compartment whose tendon passes behind the medial ankle and beneath the first metatarsal to flex the big toe. The FHL tendon is commonly used in reconstructive surgery — transferred to reinforce Achilles tendon repairs, substitute for the posterior tibial tendon in AAFD reconstruction, or augment sesamoid area repairs.

Foot Drop

An inability to dorsiflex (lift) the foot, causing a steppage gait as the patient must lift the knee excessively to clear the foot during swing phase. Caused by weakness of the tibialis anterior muscle from peroneal nerve injury, lumbar disk herniation, stroke, or neuromuscular disease. Managed with ankle-foot orthoses (AFOs) or surgical nerve repair.

Fracture

A break in the continuity of a bone. Foot and ankle fractures range from minor stress fractures (microscopic bone cracks from repetitive loading) to high-energy trauma fractures requiring surgical fixation. Treatment depends on fracture location, displacement, articular involvement, and patient factors.

G

Ganglion Cyst

A benign, fluid-filled cyst arising from a joint or tendon sheath. In the foot, ganglion cysts commonly occur on the dorsum (top) of the foot or ankle and may compress adjacent nerves or tendons, causing pain. Treated with aspiration or surgical excision when symptomatic.

Gastrocnemius Recession

A surgical procedure that lengthens the gastrocnemius muscle’s contribution to the Achilles tendon by dividing or lengthening the gastrocnemius aponeurosis at the musculotendinous junction. Used to treat equinus deformity contributing to plantar fasciitis, metatarsalgia, and diabetic foot ulcers.

Gout

A form of inflammatory arthritis caused by deposition of monosodium urate (MSU) crystals in joints and periarticular tissues, resulting from chronic hyperuricemia. The big toe MTP joint is affected in approximately 70% of first attacks (podagra). Managed acutely with NSAIDs, colchicine, or corticosteroids; long-term with urate-lowering therapy (allopurinol, febuxostat).

H

Haglund’s Deformity

An enlargement of the posterosuperior aspect of the calcaneus that irritates the retrocalcaneal bursa and Achilles tendon insertion. Also called ‘pump bump’ because of its association with rigid-backed shoes. Treated with footwear modification, heel lifts, and surgical calcaneal resection in refractory cases.

Hallux

The medical term for the big toe — the first digit of the foot. The hallux bears approximately 40–60% of body weight during the push-off phase of gait. Common hallux pathologies include bunion (hallux valgus), hallux rigidus (stiff big toe), and sesamoiditis.

Hallux Rigidus

Osteoarthritis of the first metatarsophalangeal (MTP) joint causing progressive stiffness and pain, particularly during dorsiflexion (as required for push-off in walking). Treated conservatively with stiff-soled shoes, orthotics, and injections; surgically with cheilectomy (bone spur removal) or arthrodesis in severe cases.

Hammertoe

A flexion contracture at the proximal interphalangeal (PIP) joint of a lesser toe, causing a hammer-like shape. Flexible hammertoes can be passively corrected; rigid hammertoes cannot. Causes dorsal corns, painful footwear, and plantar metatarsal calluses. Treated surgically with PIP arthroplasty or fusion.

Heel Pain

Pain in the plantar, posterior, or medial heel region. The most common cause is plantar fasciitis; other causes include insertional Achilles tendinopathy, calcaneal stress fracture, Baxter’s nerve entrapment, and fat pad atrophy. Accurate diagnosis determines appropriate treatment.

Hyperuricemia

Elevated serum uric acid (above 6.8 mg/dL), the underlying metabolic abnormality driving gout crystal formation. Caused by overproduction of uric acid, reduced renal excretion, or both. Treated with dietary modification and urate-lowering drugs when gout attacks are recurrent.

I

Ingrown Toenail (Onychocryptosis)

A condition in which the edge of a toenail penetrates the adjacent skin fold, creating a wound that may become infected. Treated definitively with partial nail avulsion and phenol matrixectomy — an in-office procedure with a 95%+ permanent cure rate.

Insertional Achilles Tendinopathy

Degeneration and pain at the point where the Achilles tendon attaches to the posterior calcaneus. Associated with Haglund’s deformity and calcification within the tendon at its insertion. Managed differently from mid-tendon Achilles tendinopathy — eccentric heel drops are contraindicated.

L

Lisfranc Injury

Fracture or ligament disruption at the tarsometatarsal (Lisfranc) joint complex of the midfoot. Frequently missed on non-weight-bearing X-rays. Unstable injuries require surgical fixation (ORIF or primary arthrodesis) to prevent midfoot collapse and post-traumatic arthritis. The Lisfranc ligament connects the medial cuneiform to the second metatarsal base.

Lymphedema

Chronic accumulation of protein-rich lymphatic fluid causing progressive, non-pitting swelling — most commonly in the legs and feet. Results from primary lymphatic malformation or secondary damage (surgery, radiation, infection). Treated with complete decongestive therapy, compression garments, and manual lymphatic drainage.

M

Mallet Toe

A flexion contracture at the distal interphalangeal (DIP) joint only (compared to hammertoe, which affects the PIP joint). Causes a downward-curving toe tip with distal corn formation. Treated with flexor tenotomy or DIP arthroplasty.

Matrixectomy

Surgical or chemical destruction of the nail matrix (nail root cells) to prevent regrowth of a nail edge. Phenol matrixectomy is the most common technique — 88% phenol is applied to the exposed matrix after partial nail avulsion to permanently prevent regrowth of the ingrown nail edge. Recurrence rate less than 5%.

Metatarsalgia

Pain in the ball of the foot (plantar metatarsal region), typically beneath one or more metatarsal heads. Caused by excessive plantar pressure from biomechanical abnormalities, hammer- or claw-toe deformities, Morton’s neuroma, or stress fractures. Treated with metatarsal pads, orthotics, or surgery.

Metatarsal

One of five long bones in the midfoot connecting the tarsal bones proximally to the phalanges (toe bones) distally. Numbered 1 (medial, adjacent to big toe) through 5 (lateral). Common pathologies include metatarsal stress fractures, Jones fracture (fifth metatarsal), and elevated metatarsal causing metatarsalgia.

Morton’s Neuroma

A perineural fibrosis (nerve thickening) of the interdigital nerve, most commonly between the third and fourth metatarsal heads. Causes burning, electric, or stabbing pain in the ball of the foot, often with the sensation of walking on a pebble. Treated with wide-toe-box footwear, metatarsal pads, corticosteroid injections, or surgical neurectomy.

MTP Joint (Metatarsophalangeal Joint)

The articulation between a metatarsal head and the proximal phalanx base of a toe. There are five MTP joints in each foot. The first MTP joint is particularly important clinically — it is the site of bunion deformity, hallux rigidus, and sesamoiditis.

N

Neuropathy (Peripheral)

Damage or dysfunction of peripheral nerves causing sensory loss, burning pain, tingling, or motor weakness in a stocking-glove distribution in the feet and legs. The most common cause is diabetes mellitus. Loss of protective sensation dramatically increases the risk of unrecognized foot injury and ulceration.

Neuroma

An abnormal growth or thickening of nerve tissue. In the foot, Morton’s neuroma (interdigital neuroma) is the most common type. True neuromas (traumatic neuromas) form after nerve injury or surgery. Treatment depends on size and symptoms — from injections to surgical excision.

O

Onychomycosis (Nail Fungus)

A fungal infection of the toenails caused by dermatophytes (most commonly Trichophyton rubrum), yeasts, or molds. Causes nail discoloration (yellow, brown, white), thickening, brittleness, and onycholysis (nail separation). Treated with topical antifungals, oral terbinafine, or laser therapy. The most prevalent nail condition in adults.

Orthotic

See Custom Orthotics. A custom-fabricated or prefabricated insole placed in the shoe to control biomechanical abnormalities, redistribute plantar pressure, or accommodate foot deformity. Prescribed by podiatrists for conditions ranging from plantar fasciitis to diabetic foot ulcer prevention.

Osteotomy

A surgical procedure in which bone is cut and repositioned to correct alignment, length, or angulation. In foot and ankle surgery, osteotomies are used to correct bunion deformity (first metatarsal), hammertoe (proximal phalanx), flatfoot (calcaneal medializing osteotomy), and high-arched foot (calcaneal lateral closing wedge).

P

PAD (Peripheral Arterial Disease)

Atherosclerotic narrowing of arteries supplying the lower extremities, causing reduced blood flow to the feet. Symptoms include claudication (calf pain with walking), rest pain, and non-healing wounds. The ankle-brachial index (ABI) is the primary screening test. PAD dramatically increases the risk of diabetic foot ulcer progression to amputation.

Peroneal Tendons

Two tendons (peroneus longus and peroneus brevis) running along the outer (lateral) ankle that evert the foot and provide dynamic lateral stability. Peroneal tendon tears, subluxation, and tendinopathy are common causes of lateral ankle pain, particularly after ankle sprains.

Plantar Fascia

A thick band of fibrous connective tissue running from the calcaneal tuberosity (heel bone) to the bases of the toes along the sole of the foot. It supports the medial longitudinal arch and acts as a tension cable during gait. Chronic microtrauma at its calcaneal origin causes plantar fasciitis.

Plantar Fasciitis

The most common cause of heel pain, resulting from degeneration and micro-tearing of the plantar fascia at its calcaneal origin. Characteristic first-step morning pain that improves with activity but worsens with prolonged loading. Treated with stretching, orthotics, night splints, shockwave therapy, PRP, and rarely surgery.

Plantar Wart (Verruca Plantaris)

A wart on the sole of the foot caused by human papillomavirus (HPV types 1, 2, 4). Appears as a hyperkeratotic lesion with black pinpoint dots (thrombosed capillaries) that interrupts normal skin lines. Treated with salicylic acid, cryotherapy, Candida antigen injection, laser, or surgical excision.

Podiatrist

A licensed Doctor of Podiatric Medicine (DPM) trained to diagnose, treat, and prevent conditions of the foot, ankle, and related lower extremity structures. Podiatrists complete 4 years of podiatric medical school, 3 years of surgical residency, and may obtain board certification from the American Board of Foot and Ankle Surgery (ABFAS).

Posterior Tibial Tendon (PTT)

The primary arch-supporting tendon of the foot, running behind the medial malleolus (inner ankle) to insert broadly across the plantar midfoot. PTT degeneration causes adult acquired flatfoot deformity (AAFD) — the most common cause of progressive flatfoot in adults.

PRP (Platelet-Rich Plasma)

An autologous blood concentrate containing a high concentration of platelets and growth factors, injected into chronic tendon, ligament, or soft tissue injuries to stimulate tissue regeneration. Used in podiatry for chronic plantar fasciitis, Achilles tendinopathy, and recalcitrant wound healing.

R

Retrocalcaneal Bursitis

Inflammation of the bursa between the Achilles tendon and the posterior heel bone, causing pain, swelling, and tenderness at the back of the heel. Associated with Haglund’s deformity and insertional Achilles tendinopathy. Treated with heel lifts, ice, NSAIDs, corticosteroid injection into the bursa (not the tendon), and shockwave therapy.

Rheumatoid Arthritis (RA)

A systemic autoimmune inflammatory arthritis that preferentially affects small joints including those of the feet and toes. Causes symmetrical MTP joint pain and swelling, hallux valgus, lesser toe deformities, and forefoot collapse. Managed with disease-modifying antirheumatic drugs (DMARDs) in coordination with rheumatology.

S

Sesamoid

One of two small bones (medial and lateral sesamoids) embedded within the flexor hallucis brevis tendon beneath the first metatarsal head. The sesamoids reduce friction, protect the tendon, and function as fulcrums for hallux flexion. Sesamoid pathology includes sesamoiditis, stress fractures, and avascular necrosis.

Sever’s Disease

Calcaneal apophysitis — a traction injury at the growth plate of the heel bone in children and adolescents aged 8–15 during periods of rapid growth. The most common cause of heel pain in this age group. Self-limiting (resolves at skeletal maturity) but managed with heel lifts, stretching, activity modification, and supportive footwear.

Stress Fracture

A microscopic bone crack resulting from cumulative repetitive loading that exceeds the bone’s rate of remodeling. In the foot, common sites are the second and third metatarsals, navicular, fifth metatarsal (Jones zone), and calcaneus. Diagnosed by MRI (plain X-rays often normal initially). Treatment depends on fracture location and risk classification.

Subtalar Joint

The articulation between the talus (ankle bone) and calcaneus (heel bone), which allows the foot to invert and evert. Subtalar motion compensates for lower limb rotation during gait. Subtalar arthritis (often post-traumatic) causes hindfoot pain and stiffness and may ultimately require subtalar fusion.

T

Talus

The ankle bone — the middle bone of the ankle joint, which articulates with the tibia above and the calcaneus below. The talus has no muscle attachments, receiving its blood supply from surrounding periosteum. This makes talar fractures and avascular necrosis particularly serious.

Tarsal Tunnel Syndrome

Compression of the tibial nerve as it passes through the tarsal tunnel — the fibro-osseous canal behind and below the medial malleolus. Causes burning, tingling, and electric pain along the inner ankle and sole. Treated with custom orthotics to correct overpronation, corticosteroid injection, or surgical tarsal tunnel release.

Tendinopathy

Chronic degeneration of a tendon — a broader, more accurate term than ‘tendinitis,’ which implies acute inflammation. Tendinopathy features disorganized collagen fibers, neovascularization, and pain. Common sites in the foot and ankle: Achilles tendon (mid-tendon and insertional), posterior tibial tendon, and peroneal tendons.

Toenail Fungus

See Onychomycosis. A fungal infection causing nail discoloration, thickening, and brittleness. The most prevalent nail condition in adults, with higher rates in diabetics, patients with peripheral arterial disease, and older individuals.

Tophus (Tophi)

A deposit of monosodium urate crystals in soft tissues, occurring in patients with chronic, poorly controlled gout. Tophi appear as firm, chalky nodules under the skin, commonly around the joints, olecranon bursa, and ear helix. Large tophi can cause joint destruction, skin ulceration, and nerve compression.

U

Ulcer (Diabetic Foot Ulcer)

See Diabetic Foot Ulcer. A full-thickness plantar foot wound in a diabetic patient, classified by depth (Wagner grades 0–5) and vascular status. The annual incidence of diabetic foot ulcers in the United States is approximately 1–4% of diabetic patients, with a 25% lifetime risk. Multidisciplinary care is required for complex ulcers.

V

Verruca Plantaris

See Plantar Wart. Latin term for a wart on the plantar surface of the foot caused by HPV. Distinguished from a callus by the interruption of skin lines and presence of black pinpoint capillary dots on paring.

Venous Insufficiency

Inadequate return of blood from the leg veins to the heart due to incompetent venous valves, causing chronic venous hypertension. Presents with bilateral ankle swelling, varicosities, skin pigmentation (lipodermatosclerosis), and venous leg ulcers above the medial ankle. Treated with compression stockings and venous ablation procedures.

W

Weil Osteotomy

A distal metatarsal osteotomy that shortens and depresses an elevated metatarsal head to relieve metatarsalgia and assist in correcting MTP joint dislocations (crossover toes). Named after Dr. Lowell Weil Sr.

Wound VAC (Vacuum-Assisted Closure)

A negative pressure wound therapy (NPWT) device that applies controlled suction to an open wound through a foam interface and airtight dressing. Removes exudate, reduces edema, promotes granulation tissue formation, and accelerates healing. Used for complex diabetic foot ulcers, surgical wounds, and dehiscent wounds.

X

X-Ray (Radiograph)

Standard plain film imaging used as the first-line imaging modality for most foot and ankle conditions. Weight-bearing X-rays are essential for accurate assessment of deformity, joint space narrowing, and stress fracture. Weight-bearing views are required for evaluating flatfoot, bunion severity, Lisfranc injuries, and ankle arthritis.

Y

YMYL (Your Money or Your Life)

A Google search quality evaluator category designating content that could significantly impact readers’ health, safety, or financial decisions. Medical content including podiatric health information falls under YMYL, requiring especially high standards for expertise, authoritativeness, and trustworthiness (E-E-A-T).

About This Glossary

This glossary was written and reviewed by Dr. Tom Biernacki DPM, board-certified podiatric surgeon and founder of Balance Foot & Ankle in Howell and Bloomfield Hills, Michigan. All definitions reflect current podiatric medical practice and are written for patient education purposes.

For questions about any of these conditions or terms, or to schedule an appointment at Balance Foot & Ankle, call (810) 206-1402 or book online. We serve patients in Howell, Brighton, Hartland, Milford, South Lyon, and all of Livingston County, Michigan.

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