Quick Answer: Adult flat feet occur when the arch collapses and the foot makes full contact with the ground. The most common cause in adults is posterior tibial tendon dysfunction. Treatment ranges from orthotics and physical therapy to surgery, depending on the stage and severity of the condition.
Flat feet in childhood often resolve on their own, but when the arch falls in adulthood, it is a different problem with different causes and different consequences. Adult-acquired flatfoot, also called adult flatfoot deformity or flexible flatfoot, affects a meaningful portion of the adult population and is one of the most common conditions treated by foot and ankle specialists across the Inland Empire, Pomona Valley, and Southern California. Summer activity levels, including increased walking, hiking, and time on your feet, often bring this condition to a head.
What Causes Flat Feet in Adults?
The arch of the foot is maintained by a combination of bones, ligaments, and, most importantly, the posterior tibial tendon (PTT). This tendon runs from the calf muscle, around the inside of the ankle, and attaches to multiple bones on the bottom of the foot. Its job is to support the arch and help the foot push off during walking.
When the posterior tibial tendon degenerates, stretches, or tears, the arch progressively collapses. This is called posterior tibial tendon dysfunction (PTTD) and is the most common cause of adult acquired flatfoot. Without tendon support, the soft tissues on the inside of the foot stretch, the heel shifts outward, and the forefoot rotates away from the body.
Other Contributing Factors
Several factors increase the risk of developing adult flatfoot:
- Obesity, which increases the mechanical load on the arch and posterior tibial tendon
- Hypertension and diabetes, which impair tendon tissue quality
- Previous foot or ankle injuries
- Inflammatory arthritis such as rheumatoid arthritis
- Age-related tissue changes that reduce tendon elasticity and strength
Symptoms: How to Recognize Adult Flatfoot
Many people with flat feet have no symptoms at all. But when symptoms do develop, they typically include:
- Pain along the inside of the foot and ankle, following the course of the posterior tibial tendon
- Swelling on the inner ankle that may be mistaken for a sprain
- Difficulty standing on the toes on one foot (a key clinical test)
- Arch and heel pain that worsens with prolonged standing or walking
- Outer ankle pain in more advanced cases, as the foot collapses and the outer bones compress
- Visible inward roll of the ankle and loss of arch height
Pain that is isolated to the outer ankle in a patient with a flat foot pattern often indicates that the deformity has progressed to a more advanced stage, as the calcaneus (heel bone) impinges on the fibula. This should prompt prompt orthopedic evaluation.
Stages of Adult Flatfoot
Orthopedic specialists classify PTTD into four stages that guide treatment decisions:
- Stage 1: Tendon inflammation without significant deformity. Pain and swelling present, but arch height preserved and single-heel-rise possible.
- Stage 2: Tendon stretched or partially torn. Arch has partially collapsed. Single-heel-rise is difficult or impossible on the affected side.
- Stage 3: Fixed deformity with rigid flat foot. Subtalar joint arthritis has developed.
- Stage 4: Ankle joint involvement with tilting of the ankle mortise.
Most patients seen in our Claremont practice are at Stage 1 or Stage 2, where non-surgical treatment has the best opportunity to succeed.
Treatment Options
Conservative Care (Stage 1 and Early Stage 2)
Non-surgical treatment is appropriate and effective for most patients with early-stage PTTD:
- Immobilization: A short period in a walking boot allows the inflamed tendon to rest and begin healing.
- Orthotics: Custom or prefabricated arch supports with medial heel wedging unload the posterior tibial tendon and provide arch support during daily activity.
- Physical therapy: Eccentric calf strengthening and posterior tibial tendon-specific exercises address the underlying tendon weakness.
- Weight management: Reducing excess body weight significantly decreases tendon load and can slow progression.
- Anti-inflammatory medication: Short-term NSAIDs reduce pain and swelling during acute flare-ups.
Surgical Treatment (Advanced Stage 2, Stage 3, Stage 4)
When conservative treatment fails or the deformity has progressed, surgery is recommended. Surgical options vary by stage and include tendon transfer procedures (using an adjacent tendon to augment or replace the failed posterior tibial tendon), calcaneal osteotomy (cutting and repositioning the heel bone to restore arch alignment), and joint fusion for rigid or arthritic deformities.
Foot and ankle surgery at Garey Orthopedic Medical Group uses current minimally invasive techniques where appropriate to achieve durable correction with efficient recovery. The right surgical procedure depends on a thorough evaluation including standing X-rays and, in some cases, MRI of the tendon.
Can Flat Feet Be Prevented From Getting Worse?
For patients with early-stage flat feet or risk factors, proactive measures can slow progression significantly:
- Wear supportive footwear with good arch support, particularly during high-activity periods in summer
- Avoid prolonged walking or standing on hard, unsupportive surfaces without orthotics
- Maintain a healthy body weight to reduce mechanical load on the tendon and arch
- Seek evaluation early if you notice inner ankle pain or swelling, rather than waiting for significant functional loss
If you're experiencing arch pain, inner ankle pain, or if you have noticed your foot becoming flatter over time, the team at Garey Orthopedic Medical Group is here to help. We offer same-day and next-day appointments for new patients. Visit gareyortho.com or call us to schedule today.