Bilateral pes planus, commonly known as flat feet, is an orthopedic condition characterized by the collapse of the foot’s natural arch. The medical term “pes planus” describes a flattened foot structure where the sole makes almost complete contact with the ground. When the condition is termed “bilateral,” this structural change affects both feet simultaneously. This is a common foot posture that can exist without causing symptoms, though it often leads to discomfort and biomechanical issues over time.
Understanding the Anatomy and Types
The human foot contains several arches, but the most important for shock absorption and support is the medial longitudinal arch, which runs along the inside of the sole. This arch is formed by the interlocking of tarsal and metatarsal bones, held in place by strong ligaments and tendons. When this structure loses integrity, the arch lowers, the heel bone may tilt outward, and the foot rolls inward, a motion called overpronation. This architectural change shifts the body’s weight distribution, affecting the mechanics of the entire lower limb.
The two main classifications of pes planus are defined by their flexibility when not bearing weight. Flexible pes planus is the most common presentation. The medial arch is visible when the person is sitting or standing on their toes, but it flattens out entirely upon standing. This type is associated with hypermobility or laxity in the ligaments and may be painless for many individuals.
In contrast, rigid pes planus involves a foot that remains completely flat whether the person is standing or sitting, meaning the arch never reappears. This structural rigidity often suggests a fixed bone deformity, such as a tarsal coalition (an abnormal connection between two bones in the foot). Because the foot cannot absorb shock or adapt to different surfaces, this type of flatfoot is more frequently associated with chronic pain.
Why the Arches Collapse
The failure of the medial arch structure is often multifactorial, resulting from a combination of inherited traits and acquired conditions. A genetic predisposition leads to natural ligamentous laxity for some individuals, meaning the supporting soft tissues are looser and allow the arch to descend more easily. This inherited flexibility can result in the common flexible flatfoot that persists from childhood into adulthood.
Age is a significant factor in the development of acquired flatfoot, often referred to as “fallen arches,” especially in adults over 40. The most frequent cause is dysfunction of the posterior tibial tendon (PTT), which is a primary stabilizer of the medial arch. Chronic inflammation or cumulative wear and tear weakens this tendon until it is no longer able to support the foot’s structure, leading to progressive collapse.
Increased mechanical stress accelerates this structural failure. Excess body weight places greater strain on the tendons, ligaments, and joints that maintain the arch, contributing to accelerated degeneration. Direct trauma, such as a fracture or severe ligament sprain, can destabilize the midfoot and lead to arch collapse. Underlying systemic conditions, including rheumatoid arthritis or diabetes-related nerve damage (Charcot foot), also compromise the integrity of the foot’s supportive tissues.
Identifying the Signs
While many people with bilateral pes planus experience no discomfort, symptoms often arise when biomechanical changes lead to overuse injuries or joint strain. The most common complaint is pain, localized in the arch, heel, or along the inner side of the ankle where the posterior tibial tendon runs. This discomfort is typically aggravated by prolonged standing, walking, or high-impact activities.
The structural change leads to visible alterations in foot and ankle alignment. The heel bone often tilts outward, causing the ankle to roll inward, a motion known as overpronation. This altered foot posture can change the walking pattern, sometimes causing an awkward or uneven gait.
Since the condition is bilateral, patients frequently experience symmetrical symptoms, noticing that both feet tire easily and feel fatigued after minimal activity. The change in alignment transmits abnormal stress up the leg, leading to secondary pain in the shin (shin splints), knee, hip, and lower back. Swelling along the inside of the ankle, correlating with a strained posterior tibial tendon, is also an observable sign.
Approaches to Relief and Correction
Management strategies for bilateral pes planus focus primarily on reducing pain, improving function, and preventing the progression of deformity. Non-surgical intervention is the initial approach and often provides significant relief for flexible flatfoot. Custom-made or over-the-counter arch supports, known as orthotics, are a foundational treatment, working to mechanically support the fallen medial arch and limit excessive pronation during standing and walking.
Physical therapy plays a significant role in improving the foot’s intrinsic support system. Specific exercises often target strengthening the muscles responsible for dynamic arch support, particularly the posterior tibial tendon. Stretching exercises for the calf and Achilles tendon are also commonly prescribed, as tightness in these areas increases the forces that flatten the arch.
Lifestyle modifications are recommended to decrease the overall load placed on the foot’s supporting structures.
Non-Surgical Treatments and Lifestyle Changes
- Maintaining a healthy body weight to decrease the overall load placed on the foot’s supporting structures.
- Wearing supportive footwear with a sturdy heel counter and adequate arch support.
- Avoiding shoes like sandals or those with minimal structure.
- Using non-steroidal anti-inflammatory drugs (NSAIDs) temporarily for managing acute pain and inflammation.
Surgical correction is generally reserved for rigid flatfoot or severe acquired cases that have failed to respond to extensive conservative management. These procedures are complex and may involve repairing or transferring a damaged tendon, such as the posterior tibial tendon. Other surgical options include osteotomies, which involve cutting and repositioning bones to restore the arch’s natural shape, or in cases of severe arthritis, joint fusion (arthrodesis) to stabilize the hindfoot.