Adult pes planus — also known as flat foot or fallen arches — is a condition in which the inner (medial) arch of the foot collapses, so that more of the sole comes into contact with the ground when standing.

When the supporting tendons, ligaments, and bones lose their alignment, the arch flattens, the heel drifts outwards (hindfoot valgus), and the forefoot rotates outwards (forefoot abduction). Adult-acquired flat foot is now also described as Progressive Collapsing Foot Deformity (PCFD), a term that recognises the multi-planar nature of the problem.

Specialist assessment by a Consultant Foot & Ankle Surgeon — such as Mr Matthew Welck in London — gives patients with flat foot, fallen arches, or sports-related arch pain access to the widest range of joint-preserving and reconstructive treatment options.

Some degree of flat foot is present in approximately 20–30% of UK adults, although many remain entirely asymptomatic. Symptomatic adult-acquired flat foot affects an estimated 3–10% of adults, with prevalence rising sharply over the age of 40 and a higher incidence in women.

Risk factors include obesity, hypertension, diabetes, and inflammatory arthritis. Sports injuries — particularly running, racquet sports, football, and high-impact pivoting activities — can also accelerate posterior tibial tendon failure, which is why early specialist review is important for active patients across London, North London, and Hertfordshire.

The leading cause is Posterior Tibial Tendon Dysfunction (PTTD), now grouped under Progressive Collapsing Foot Deformity (PCFD). The posterior tibial tendon is the key dynamic stabiliser of the medial arch; when it becomes inflamed, elongated, or torn, the spring ligament and other static stabilisers come under increasing strain and gradually fail.

Other recognised causes include:

• Spring ligament tears and deltoid ligament insufficiency
• Trauma — fractures of the calcaneus, talus, or midfoot (particularly Lisfranc injuries)
• Inflammatory arthritis, including rheumatoid arthritis
• Charcot neuroarthropathy in patients with diabetes
• Tarsal coalition and untreated paediatric flat foot progressing into adulthood
• Iatrogenic causes following previous foot surgery
• Neuromuscular causes such as cerebral palsy

Symptoms of adult pes planus typically progress through clinical stages. Patients in the early stages often describe inner ankle and hindfoot pain that is mistaken for a sports injury, while later stages cause outer sided pain, then obvious deformity and stiffness.

Common symptoms include:

• Pain and swelling along the inner ankle, behind the medial malleolus, along the posterior tibial tendon
• Visible flattening of the arch, with the heel drifting outwards
• The “too many toes” sign when viewed from behind
• Difficulty performing a single-leg heel raise on the affected side
• Lateral (outer) ankle pain in advanced disease, due to impingement of outer structures
• Fatigue, calf tightness, and reduced sporting performance
• Stiffness and arthritis as the deformity becomes rigid in late stages

Accurate staging of adult flat foot is essential because treatment depends on whether the deformity is flexible or rigid, and on whether arthritis has developed. Mr Welck routinely uses the following investigations:

• Weight-bearing X-rays of the foot and ankle to assess alignment and any arthritis
• Weight-bearing CT (WBCT) — increasingly the gold standard for understanding three-dimensional deformity, including subtalar and subfibular impingement. It is Mr Welck’s imaging of choice.
• MRI to evaluate the posterior tibial tendon, spring ligament, deltoid ligament, and articular cartilage
• Ultrasound for dynamic assessment of the tendon
• Blood tests where inflammatory or metabolic conditions are suspected

Most patients with flat foot or fallen arches are managed without surgery, particularly in the early stages. The aim is to support the arch, offload the failing tendon, and treat any underlying contributors.

Non-surgical options include:

• Custom orthotics with medial arch support and heel posting. Mr Welck works closely with orthotists to make bespoke orthotics. They tend to work well with flexible deformities that can be corrected, but are less helpful with stiff, rigid ones.
• Bracing for more advanced flexible deformity
• Activity modification and footwear advice (supportive trainers, avoidance of unsupportive shoes)
• Targeted physiotherapy — eccentric tibialis posterior strengthening, calf stretching, intrinsic foot muscle training
• Weight management
• Image-guided injections (steroid is generally avoided within the tendon itself but can be helpful on the outside of the foot)
• Optimisation of co-existing conditions such as diabetes or inflammatory arthritis

When non-surgical treatment fails, or when deformity is progressing, surgery is offered to restore alignment, offload the failed tendon, and prevent progression to arthritis. Procedures are tailored to the stage of disease and to the patient’s functional goals.

Joint-Preserving Reconstruction (flexible deformity):

Each deformity and patient is different and an individualised plan is required tailored to your deformity and examination. Some of the options that can be used include:

• Flexor Digitorum Longus (FDL) tendon transfer to the navicular, to pull up the inner arch, give it support, and take over the role of the failing inner tendons.
• Medialising Calcaneal Osteotomy (MCO), to surgically break the heel and shift it from an outward to a normal position.
• Lateral Column Lengthening (Evans osteotomy)
• Arthroreisis screw — a special screw placed on the outside of the hindfoot to help push the foot inwards, which Mr Welck is keen to use in flexible deformities.
• Cotton osteotomy (medial cuneiform plantar-flexion osteotomy) — used if the foot remains twisted after correction of the hindfoot.
• Spring ligament repair or reconstruction
• Gastrocnemius recession (Strayer / Silverskilold procedure), if the heel cord is tight.

Joint-Sacrificing Surgery (rigid deformity or established arthritis):

• Subtalar arthrodesis
• Double or triple arthrodesis
• Lisfranc / midfoot fusion when midfoot collapse predominates

Mr Welck performs the full spectrum of these procedures at the Royal National Orthopaedic Hospital and at his private clinics across London, North London, and Hertfordshire.

Mr Matthew Welck is a Consultant Orthopaedic Foot & Ankle Surgeon at the Royal National Orthopaedic Hospital (RNOH) Stanmore — the UK’s largest specialist orthopaedic hospital — and Honorary Associate Clinical Professor at UCL. He is widely recognised as one of the leading foot and ankle surgeons in London, North London, and Hertfordshire, with subspecialty expertise across the full breadth of foot and ankle surgery, including:

• Total ankle replacement and complex ankle reconstruction
• Adult flat foot (pes planus) reconstruction and posterior tibial tendon surgery
• Sports injuries of the foot and ankle, including tendon, ligament, and cartilage problems
• Hallux rigidus, bunions, and forefoot reconstruction
• Cartilage repair and joint-preserving surgery of the ankle
• Revision foot and ankle surgery and management of complex deformity

With over 50 peer-reviewed publications, double fellowship training, and a regular tertiary referral practice, Mr Welck offers patients across London, North London, and Hertfordshire access to the latest joint-preserving and reconstructive techniques, including weight-bearing CT planning, total ankle replacement, and modern fixation systems. Tertiary referrals are accepted from GPs, physiotherapists, podiatrists, and consultant colleagues nationally.

Areas We Cover

Mr Welck consults at multiple private clinic locations and accepts patients from across the following areas. The Royal National Orthopaedic Hospital (RNOH) Stanmore sits on the border of North London and Hertfordshire, providing convenient access for patients from both regions.

• Central London — including Harley Street, Marylebone, the City, and surrounding areas
• North London — including Stanmore, Edgware, Barnet, Finchley, Hampstead, Highgate, Mill Hill, Enfield, and Wood Green
• Hertfordshire — including Watford, Bushey, Borehamwood, Radlett, Elstree, St Albans, Hertford, Hatfield, Rickmansworth, and surrounding towns
• Greater London and the Home Counties — by referral for complex foot and ankle problems

Mr Welck consults at multiple private clinic locations across London and North London, as well as the Royal National Orthopaedic Hospital. To arrange a consultation for flat foot, fallen arches, posterior tibial tendon problems, or sports injuries of the foot and ankle, please get in touch.

• Phone: 07547 395 270
• Web: matthewwelck.com
• Practice: Stanmore Foot & Ankle Specialists  ·  Royal National Orthopaedic Hospital, Stanmore  ·  UCL

Medical Disclaimer: This page is intended as general information for patients with adult pes planus, flat foot, fallen arches, or related foot and ankle problems. It is not a substitute for individual medical advice. Please consult a qualified Consultant Orthopaedic Foot & Ankle Surgeon for assessment and treatment recommendations specific to you.