Flat Feet

Pes planus: loss or reduction of the medial longitudinal arch of the foot, usually with hindfoot valgus and forefoot abduction.

• Types:
  • Flexible flatfoot: the arch is lost on standing and reappears when the patient stands on tiptoe or when the great toe is dorsiflexed, with a normal range of subtalar movement. It is physiological in infants and toddlers (most arches develop by 6 to 10 years), is present in about 15 to 25% of adults, and is usually painless.
  • Rigid flatfoot: the arch is absent in all positions and subtalar movement is restricted, due to tarsal coalition (a bony or fibrous bridge between the calcaneus and navicular or the talus and calcaneus, in about 1 to 2% of people), congenital vertical talus, inflammatory arthritis, post-traumatic or neuropathic (Charcot) deformity.
  • Adult acquired flatfoot deformity (posterior tibial tendon dysfunction): progressive collapse in middle aged and older adults, more often women, with obesity, hypertension, diabetes, inflammatory arthritis, steroid use and previous trauma as risk factors.
• Other contributors: ligamentous laxity (Marfan, Ehlers-Danlos, Down syndrome), tight Achilles tendon, obesity, pregnancy, and neuromuscular disease (cerebral palsy).
• Most flexible flat feet in children need no treatment. In adults, symptoms arise from tendon overload, plantar fascia strain, sinus tarsi impingement, medial column strain and later arthritis.

• Children: usually asymptomatic. Some have fatigue, aching in the foot and leg, clumsy gait, or shoe wear on the inner border. Pain or a limp is unusual and needs assessment.
• Adults: arch collapse, foot and ankle pain (medial, along the posterior tibial tendon behind the medial malleolus, or lateral, from sinus tarsi and fibular impingement), swelling over the medial ankle, fatigue after standing, and progressive deformity.
• Examination (standing and walking): hindfoot valgus ("too many toes" sign, where more toes are seen lateral to the heel from behind), forefoot abduction, flattened arch, heel not rising into varus on single leg heel raise (a sign of posterior tibial tendon failure, or inability to perform it), tenderness along the posterior tibial tendon, and tight gastrocnemius or Achilles tendon (equinus). The arch re-forms with great toe dorsiflexion in flexible disease.
• Rigid flatfoot: limited subtalar movement, peroneal spasm (painful, rigid spastic flatfoot in tarsal coalition, in adolescents at 8 to 16 years), and frequent ankle sprains.
• Differential diagnosis: tarsal coalition, congenital vertical talus, neuromuscular disease (cerebral palsy, spina bifida), ligamentous laxity syndromes, accessory navicular, posterior tibial tendon rupture, tibialis posterior tenosynovitis, rheumatoid arthritis, Charcot neuroarthropathy, and post-traumatic deformity.
• Red flags: a rigid foot, severe pain or limp in a child, rapid progression, unilateral flat foot of recent onset in an adult, neurological signs, and diabetic neuropathy with a warm swollen foot.
• Complications: posterior tibial tendon rupture, progressive deformity, ankle valgus and deltoid ligament failure, arthritis of the subtalar, talonavicular and ankle joints, plantar fasciitis, bunion, knee and hip pain, and ulceration over the collapsed midfoot in neuropathic feet.

• Clinical examination standing, walking, on tiptoe and seated, with assessment of subtalar movement, ankle dorsiflexion (for equinus), tendon function and neurovascular status.
• Weight bearing X-rays (anteroposterior and lateral of the foot, and ankle) show arch height (lateral talar to first metatarsal angle), talonavicular uncoverage, hindfoot alignment and arthritis. A hindfoot alignment view for hindfoot valgus.
• CT for tarsal coalition (bony bars) and complex deformity. MRI for posterior tibial tendon tears, spring ligament injury, fibrous or cartilaginous coalition, and sinus tarsi pathology. Ultrasound for tendon sheath fluid and tears.
• In adults with new unilateral flat foot, check for tendon rupture, trauma, diabetes (neuropathic collapse), and inflammatory arthritis (CRP, ESR, rheumatoid markers).

• Asymptomatic flexible flatfoot in children and adults: no treatment is needed. Explain that most children develop an arch by 6 to 10 years and that orthoses and special footwear do not change the natural history.
• Symptomatic flexible flatfoot:
  • Supportive, well fitting shoes with a firm heel counter and good arch support.
  • Prefabricated or custom orthoses (a medial arch support with a deep heel cup and medial heel wedge) worn at all times when standing or walking, which reduce pain in most patients and slow progression.
  • Calf and Achilles stretching (30 seconds, 3 times, twice daily), strengthening of the tibialis posterior and intrinsic foot muscles (heel raise with inversion, band resisted inversion, short foot exercises, 3 sets of 10 to 15), and hip and core strengthening.
  • Weight loss, activity modification, and avoidance of barefoot walking on hard surfaces.
  • Analgesia: paracetamol 1 g orally 6 hourly, ibuprofen 400 mg orally 8 hourly with food (or naproxen 500 mg 12 hourly) for 1 to 2 weeks, and topical diclofenac 1% gel 2 to 4 g 3 to 4 times daily.
• Posterior tibial tendon dysfunction (staged by flexibility and deformity):
  • Early (tenosynovitis, flexible, tendon intact): immobilisation in a walking boot or short leg cast for 6 to 8 weeks, then a custom orthosis or an ankle foot orthosis, with physiotherapy for 3 to 6 months. About 60 to 70% improve without surgery.
  • Corticosteroid injection around the tendon sheath is avoided because of rupture risk.
  • Flexible deformity with tendon failure: surgery (debridement, flexor digitorum longus tendon transfer to the navicular, medial displacement calcaneal osteotomy, with or without lateral column lengthening and spring ligament reconstruction), with 6 to 12 weeks of non-weight bearing or protected weight bearing and about 80 to 90% good results.
  • Rigid deformity with arthritis: arthrodesis (subtalar, double or triple arthrodesis), and for ankle valgus, deltoid reconstruction or tibiotalar procedures.
• Tarsal coalition: rest, a walking boot or short leg cast for 3 to 6 weeks, orthoses and NSAIDs for initial treatment. Surgery for persistent pain (bar resection with interposition of fat or muscle for coalitions involving less than 50% of the joint without arthritis, and fusion for extensive coalition or arthritis).
• Children with pathological flatfoot (rigid, painful, or neuromuscular): refer to paediatric orthopaedics. Surgery (calcaneal lengthening or subtalar arthroereisis) is considered for symptomatic, flexible deformity that fails 6 to 12 months of non-operative care.
• Diabetic Charcot foot: total contact casting and non-weight bearing until stable, followed by custom footwear and surgical correction for unstable or ulcerated deformity.
• Special groups:
  • Pregnancy: arch collapse and swelling are common and often settle after delivery. Use supportive shoes, orthoses and paracetamol. Avoid NSAIDs after 20 weeks.
  • Obesity and diabetes: weight loss and glucose control, and daily foot checks.
  • Elderly: assess for tendon rupture and arthritis, and use ankle foot orthoses when surgery is not suitable.
  • Athletes: orthoses, footwear adjustment, and graded return.
  • Renal impairment and gastrointestinal disease: avoid oral NSAIDs.
• Follow up: children every 6 to 12 months during growth if symptomatic. Adults review at 6 to 12 weeks, then every 3 to 6 months while deformity or pain progresses. Refer to orthopaedics or podiatry for rigid foot, pain in a child, progressive adult deformity, tendon rupture, or failure of 3 to 6 months of treatment.