Acquired Foot Deformities in Adults: Causes, Progression and Podiatric Therapy

What lies behind it

The human foot is a complex masterpiece of evolution. It consists of 26 bones, 33 joints, and more than 100 muscles, tendons, and ligaments. These structures work precisely together to support the entire body weight and cushion impacts with every step. The arch of the foot is divided into a longitudinal arch on the inside and a transverse arch in the midfoot region. These arch structures are supported by passive ligamentous structures such as the plantar aponeurosis, as well as by dynamic muscular guidance. The tibialis posterior muscle plays a central role in maintaining the longitudinal arch, while the short intrinsic foot muscles stabilize the transverse arch.

When structural changes occur in adulthood, specialists refer to an acquired foot deformity. In contrast to congenital malalignments, acquired deformities develop over the course of life due to impaired biomechanics. One of the most common forms is adult acquired flatfoot deformity, often referred to in international medical literature as Adult Acquired Flatfoot Deformity. This frequently involves insufficiency of the tibialis posterior tendon. The tendon loses its tension, the longitudinal arch flattens, and the calcaneus tilts inwards.

Another widespread structural change affects the transverse arch. When this arch flattens, it is referred to as splayfoot. The metatarsal bones fan outward, placing excessive load on metatarsal heads II to IV. Due to the altered line of pull of the tendons, a splayfoot frequently develops into a hallux valgus. In this deformity, the first metatarsal bone deviates medially, while the hallux angles laterally at the metatarsophalangeal joint toward the second toe. A prominent bunion forms, which is prone to inflammation.

On the lesser toes, an impaired muscular balance between the long and short toe flexors and extensors leads to characteristic toe deformities. In a hammer toe, the distal phalanx is extended while the middle phalanx is flexed at the interphalangeal joint. A claw toe, by contrast, exhibits dislocation or subluxation at the metatarsophalangeal joint with flexion at both the proximal and distal interphalangeal joints. A tailor's bunion, also known as a bunionette, involves an outward deviation of the fifth metatarsal bone, leading to painful pressure points on the outer margin of the foot.

Typical signs

Acquired changes in the foot often manifest initially through non-specific discomfort. At first, affected individuals frequently report a diffuse feeling of fatigue in the lower legs after prolonged standing or walking. As the condition progresses, the pain becomes localized. When the transverse arch collapses, metatarsalgic pain often occurs directly under metatarsal heads II to IV. Thicker plaques of callus, known as hyperkeratoses, form under the skin at these locations as a natural protective mechanism against increased pressure.

Another clear symptom is mechanical irritation at the toe joints. In hammer and claw toes, the skin rubs against the upper part of the footwear. Painful corns, known medically as clavi, develop where a central keratin plug penetrates deep into the dermis and presses against sensitive nerve endings. At the site of a hallux valgus, a subcutaneous bursitis frequently develops over the bony prominence. This area becomes red, swollen, and painful even under light touch.

These purely biomechanical complaints must be differentiated from inflammatory systemic diseases. A Morton's neuroma, for example, manifests as paroxysmal, burning pain radiating into the toes, caused by perineural fibrosis of the interdigital nerve. Rheumatoid arthritis also leads to toe deformities, but shows characteristic joint erosions on radiographs and is accompanied by systemic markers of inflammation. An acute attack of gout preferentially affects the first metatarsophalangeal joint, but occurs suddenly and is accompanied by extreme erythema and localized warmth.

A typical case from daily podiatric practice illustrates this presentation in a 54-year-old shop assistant. She complained of burning pain beneath her forefoot that had increased over several months, as well as friction points on the second toe. Physical examination revealed a completely flattened transverse arch, marked hyperkeratosis under the second metatarsal head, and early claw toe formation of the second toe. Only the combination of targeted callus reduction and individual pressure relief brought the desired pain relief in her daily working life.

Everyday causes

The development of acquired foot deformities is significantly influenced by daily factors and lifestyle habits. A major external driver is unsuitable footwear. Shoes that are too tight compress the toes and prevent the natural splaying movement during stance and push-off. High heels shift weight distribution drastically forward. With a heel height of five centimetres, up to 80 percent of the body weight is transferred to the forefoot. The transverse arch cannot biomechanically withstand this continuous load and inevitably collapses.

Alongside footwear, occupational strain plays a central role. Prolonged standing on hard industrial floors or tiles with minimal cushioning overloads the passive ligamentous support of the foot. As the strength of the fatigued foot muscles wanes over the course of the day, the ligaments absorb the loads. Over years, the long plantar ligament (ligamentum plantare longum) and the ligamentous apparatus of the tarsus stretch, resulting in an irreversible yielding of the arch structures.

Systemic factors and hormonal changes accentuate these processes. During menopause, falling oestrogen levels impair collagen synthesis and weaken connective tissue. Ligaments lose elasticity, rendering the arch of the foot more unstable. Excess body weight represents a continuous additional load, increasing the force of every step by a multiple of body weight. Furthermore, shortening of the calf musculature, particularly the gastrocnemius muscle, restricts dorsiflexion in the ankle joint. The foot compensates for this deficit through excessive pronation during the stance phase, accelerating the collapse of the longitudinal arch.

Improper foot care can also promote abnormal loading. If pain is avoided by incorrectly trimming toenails, affected individuals often unconsciously shift weight onto the outer border of the foot. This antalgic posture alters the gait pattern permanently and creates new biomechanical overload zones elsewhere.

When medical evaluation is required

Not every foot change requires immediate surgical intervention, but certain warning signs necessitate prompt specialist evaluation by an orthopaedic surgeon or dermatologist. A sudden collapse of the foot structure without adequate trauma may indicate a tendon rupture, such as a tear of the tibialis posterior tendon. In this situation, the stability of the longitudinal arch is rapidly lost, and conservative therapy alone is usually no longer sufficient.

Acute signs of inflammation also demand medical attention. If the area surrounding a deformity is severely reddened, hot, and swollen, a bacterial infection or acute bursitis must be ruled out. In individuals with diabetes mellitus or peripheral arterial disease, heightened caution is required. Painless pressure sores or open wounds (ulcerations) can be signs of diabetic foot syndrome and require immediate medical care.

Furthermore, weight-bearing radiographic examination is indicated when deformities become completely rigid. As long as a toe or the arch of the foot can be manually corrected passively, specialists refer to a flexible deformity. If the joint can no longer be moved into its anatomical position, a rigid deformity with arthritic remodeling is present. In such cases, medical clarification is needed to determine whether diagnostic imaging such as digital radiography or MRI is necessary to initiate surgical corrections or specific custom orthopaedic footwear provision.

What podiatric treatment can achieve

Podiatry plays a key role in the management of acquired foot deformities at the interface between dermatology, orthopaedics, and patient daily life. A thorough podologische Komplexbehandlung (comprehensive podiatric treatment) always begins with a detailed assessment. Skin condition, pressure distribution, joint mobility, and nail morphology are recorded in detail. This documentation enables progress monitoring over extended treatment periods.

Central to the treatment is the professional reduction of painful hyperkeratoses and corns. Using sterile scalpel blades and rotating instruments, cornified tissue layers are precisely removed. Podiatrists work here with micromotor rotational instruments under spray cooling to prevent thermal tissue damage. Following reduction, the localized pressure pain usually subsides immediately, providing instantaneous relief during walking. Information on exact treatment procedures can be found in the /en/services section of our website.

A key element of podiatric therapy is the fabrication of custom silicone orthoses. These tailor-made pressure- and friction-relief appliances are moulded directly on the patient's foot using medical-grade two-component silicones. Depending on the indication, different Shore hardness levels are applied. Soft silicones with low Shore hardness provide pure pressure relief on painful corns or tailor's bunions. Medium to hard silicones are used to gently correct flexible toe deformities or to prevent toes from overlapping. A well-fitted orthosis redistributes mechanical forces and protects the skin against the recurrent risk of ulcers or corns.

If the toe deformity leads to nail changes, for instance due to constant pressure of the toe apex against the toe cap of the shoe, refined techniques such as nail correction braces (orthonyxia) are employed. These corrective braces relieve the nail fold and prevent the nail plate from becoming ingrown. As a sektorale Heilpraktikerin (sectorally authorised practitioner for podiatry, available at /en/sectoral-practitioner), Helga Maria Freitag also holds the qualification to make independent podiatric diagnoses and initiate targeted therapy plans without a prior physician visit. Treatment intervals depend on findings and generally range between four and six weeks.

What you can do yourself

Affected individuals can positively influence the course of an acquired foot deformity through a consistent self-exercise program and targeted lifestyle adaptations. Activating the intrinsic foot muscles is the most crucial component.

• Perform Janda's short foot exercise daily, actively drawing the forefoot toward the heel without clawing the toes to lift the longitudinal and transverse arches.
• Regularly stretch the calf muscles using wall lunge exercises to reduce pull on the Achilles tendon and improve the roll-off motion of the foot.
• Pick up small objects such as marbles or a tissue with your toes to promote mobility in the metatarsophalangeal and interphalangeal joints.
• Walking barefoot on soft, uneven natural ground such as grass, sand, or forest soil stimulates proprioceptors and strengthens muscular stabilization.
• When buying shoes, ensure a sufficiently wide toe box, flat heels, and a flexible sole in the area of the metatarsophalangeal joints.
• Care for the skin daily with a urea-containing emulsion with a urea content of 10 to 15 percent to maintain the elasticity of the stratum corneum and prevent fissures.

Common mistakes

In clinical practice, well-intentioned but inappropriate measures frequently worsen the condition of acquired foot deformities.

• Self-treatment with razor blades, corn planes, or aggressive scissors carries an immense risk of injury and infection.
• Using over-the-counter corn plasters containing salicylic acid frequently causes chemical burns to the surrounding healthy tissue and deep wounds.
• Switching permanently to extremely soft, unstable plastic shoes without heel support exacerbates dynamic pronation and leads to even faster fatigue of the foot muscles.
• Wearing off-the-shelf insoles from supermarkets without individual biomechanical analysis often alters biomechanics in an uncontrolled manner and increases pressure at the wrong locations.
• Ignoring mild initial pain causes flexible, easily treatable deformities to become stiff and rigid.

Current evidence and classification

Medical research in recent years highlights the importance of conservative and podiatric interventions in acquired foot deformities. A systematic review demonstrates that custom orthopaedic appliances and professional pressure protection can significantly reduce pain intensity in plantar fasciitis and forefoot pain [1]. The combination of targeted muscle training and biomechanical offloading has been shown in clinical trials to slow the progression of moderate hallux valgus deformities [2].

Studies on adult acquired flatfoot deformity demonstrate that early non-surgical therapy in stages I and II can halt the progression of tendon degeneration [3]. Evidence studies show that regular podiatric reduction of hyperkeratoses not only leads to an immediate reduction in peak local pressure values under the metatarsal heads, but also sustainably improves gait pattern and step stability in older adults [4]. In addition, research shows that targeted training of the toe flexors noticeably reduces the risk of falls in older adults with foot deformities [5].

Treatment in Memmingen

For patients in the Memmingen area, the Unterallgäu, and the neighbouring regions of Upper Swabia and the Allgäu, FREITAG® Podologie GmbH provides a professional and specialized point of contact. In the modern treatment rooms at Kempterstr. 25, the team led by Helga Maria Freitag focuses on the preventive and therapeutic management of acquired deformities. The highest standards of hygiene are our top priority, as detailed on our /en/hygiene page. You can gain insight into our facilities and treatment options via the /en/practice section. An individual initial consultation can be arranged at any time.

Orthopaedic insoles and footwear modifications

Targeted orthopaedic insole provision not only corrects the collapsed arch, but also alters dynamic ground reaction forces during gait. Specialists generally distinguish between passive-supportive and sensorimotor insoles. Passive-supportive systems made of rigid cork-leather composites or thermoplastic polymers realign the calcaneus. They mechanically unload the sustentaculum tali as well as the plantar fascia. In managing an acquired splayfoot, a retrocapital or metatarsal pad is frequently used. This teardrop-shaped pad made of soft polyurethane foam is positioned directly behind metatarsal heads II to IV to elevate the transverse arch in a targeted manner.

Sensorimotor insoles, on the other hand, utilize targeted pressure prompts applied to the tendon insertions of the intrinsic and extrinsic foot muscles. Small elevations beneath the sustentaculum tali or the tendon of the peroneus longus muscle activate neuromuscular reflexes. The musculature responds with altered baseline tension. Insoles made of ethylene-vinyl acetate (EVA) offer various Shore hardness levels. For diabetic patients or sensitive pain patients, orthopaedic shoe technicians often select a soft Shore hardness of 15 to 20. Sporty, active individuals, by contrast, typically require material densities of 35 to 45 Shore to adequately support the arch dynamically.

Complementing the insole, orthopaedic shoe technology offers effective modifications to off-the-shelf footwear. A butterfly rocker relieves the central metatarsal heads through soft cushioning and a targeted recess in the outsole. The metatarsal roller shifts the roll-off point of the shoe backward behind the metatarsophalangeal joints. This noticeably unloads the forefoot during walking, as painful flexion in the first metatarsophalangeal joint is minimized.

Physical therapy and functional movement concepts

Alongside passive management, active physical therapy restructuring of foot geometry forms a fundamental cornerstone. The Spiraldynamik movement concept views the foot as a twisted spiral structure. During the roll-off motion, the hindfoot rotates outward while the forefoot rotates inward into a pronated position. Through targeted coordination and strength training, affected individuals learn to consciously recreate this anatomical torque in daily life. Exercises performed three times a week over at least twelve weeks demonstrate measurable success in clinical practice in restoring the longitudinal arch during early-stage tibialis posterior insufficiency.

Supporting structures tend to develop secondary inflammatory processes in chronic deformities. In concomitant plantar fasciitis or Achilles tendon irritation, focused or radial extracorporeal shockwave therapy (ESWT) is applied. High-energy acoustic transmitters convey mechanical pressure waves into the tissue. This stimulates neovascularization and promotes the release of growth factors such as TGF-beta1. Following three to five sessions at weekly intervals, many patients report a significant reduction in morning stiffness and start-up pain.

Functional taping offers effective support in the acute stage. Kinesiology tape is applied under tension fanned along the tibialis posterior tendon or transversely across the transverse arch. It mechanically relieves overstretched tissue while simultaneously enhancing proprioceptive awareness. A case from physical therapy practice illustrates the benefit: a 48-year-old female hiker from Upper Swabia reduced her medial malleolar discomfort through a three-week combination of taping applications and targeted eccentric calf muscle training to the extent that symptom-free walking distances of ten kilometres were achievable again.

Surgical correction procedures and postoperative care

If conservative therapies over a period of six to twelve months fail to yield adequate pain relief, or if a rigid, painful deformity is present, corrective surgical procedures are considered. In hallux valgus correction, osteotomies (bony realignments) are performed. The Chevron or Austin osteotomy is suitable for mild to moderate deformities. In this procedure, the surgeon performs a V-shaped cut through the distal end of the first metatarsal bone and shifts it laterally. For more pronounced findings, the Scarf osteotomy with a Z-shaped bone cut offers higher mechanical stability.

If instability is additionally present in the first tarsometatarsal joint, Lapidus arthrodesis represents the procedure of choice. The affected joint is fused and firmly fixed with plates or screws. To correct painful hammer toes or metatarsalgia, a Weil osteotomy of metatarsal bones II to IV is often performed. The metatarsal bone is slightly shortened and elevated to immediately reduce pressure beneath the metatarsal heads.

Postoperative care requires a strict rehabilitation protocol. Following surgery, patients wear a special forefoot offloading shoe for four to six weeks. This shoe prevents roll-off over the forefoot and protects bony healing. Podiatric follow-up care gains importance after suture removal. Scar tissue along incision lines must be mobilized to prevent adhesions with underlying tendons. Through gentle manual scar massage and the application of moisturizing silicone sheets, the tissue remains pliable, effectively preventing recurrent pain in the corrected foot.