Month: September 2026

Adult-Acquired Flatfoot: How Posterior Tibial Tendon Dysfunction Affects the Foot

x-ray of a person with flat foot

Reviewed by Kevin L. Kirk, D.O., F.A.O.A.

Flat feet can occur for many reasons, and not everyone with a low or flattened arch experiences pain. Some people have flexible flat feet from childhood and remain active without limitations. Others develop a progressively collapsing arch as adults because the posterior tibial tendon, the tendon that helps support the arch and control foot movement—becomes stretched, inflamed, weakened, or torn.

This condition is commonly known as adult-acquired flatfoot deformity or posterior tibial tendon dysfunction (PTTD). The American Orthopaedic Foot & Ankle Society (AOFAS) also describes this condition as progressive collapsing foot deformity. Without appropriate evaluation and treatment, the foot may gradually lose its arch, roll inward, and become painful or unstable.

At TSAOG Orthopaedics and Spine Foot & Ankle Institute’s experienced foot and ankle surgeons can evaluate painful or progressive flatfoot and recommend treatment based on the condition’s severity, cause, and effect on your daily activities.

What Is Adult-Acquired Flatfoot?

Adult-acquired flatfoot occurs when the arch gradually collapses after it previously developed normally. One of the most common causes is dysfunction of the posterior tibial tendon.

The posterior tibial tendon runs along the inside of the ankle and attaches to bones in the foot. It helps support the arch and assists with turning the foot inward while walking. When the tendon becomes damaged or stops functioning properly, the arch may gradually flatten, and the heel may shift outward.

This can change the alignment of the entire foot. In addition to tendon dysfunction, the ligaments and joints that support the arch may also become strained or damaged over time.
Adult-acquired flatfoot is different from the flexible flat feet that many people have since childhood. It is more likely to progress and cause pain, weakness, instability, or difficulty walking.

What Causes Posterior Tibial Tendon Dysfunction?

Posterior tibial tendon dysfunction may result from gradual wear and tear, overuse, an injury, or conditions that place additional stress on the foot. Risk factors may include:

  • Increasing age, particularly after age 40
  • Being overweight or obese
  • Diabetes
  • High blood pressure
  • Previous ankle or foot injuries
  • Repetitive walking, standing, or high-impact activity
  • Inflammatory conditions such as rheumatoid arthritis
  • A naturally flat or poorly aligned foot

The condition is more common in women and in adults over 40, although it can affect anyone.

What Are the Symptoms of Adult-Acquired Flatfoot?

Symptoms may develop gradually and become more noticeable with prolonged standing, walking, or physical activity. Common signs include:

  • Pain or tenderness along the inside of the ankle or arch
  • Swelling along the posterior tibial tendon
  • A flattening or loss of the arch
  • The heel shifting outward
  • The foot rolling inward while standing or walking
  • Weakness when trying to stand on the toes
  • Difficulty walking on uneven ground
  • Reduced balance or foot stability
  • Fatigue in the foot or leg
  • Pain that worsens with activity and improves with rest
  • A change in shoe fit or uneven shoe wear

As the condition progresses, pain may spread to the outside of the ankle or the top and middle portions of the foot. Some patients eventually develop stiffness or arthritis in the joints of the hindfoot.

A simple sign of posterior tibial tendon dysfunction is difficulty performing a single-leg heel raise. A patient may be unable to rise onto the toes of the affected foot or may experience pain and weakness while attempting to do so.

How Is Adult-Acquired Flatfoot Diagnosed?

Diagnosis begins with a medical history and physical examination. A foot and ankle surgeon may assess:

  • The shape of the arch while standing and sitting
  • Foot and ankle alignment
  • Tenderness or swelling along the posterior tibial tendon
  • The ability to perform a heel raise
  • Strength and range of motion
  • Walking pattern and balance
  • Flexibility or stiffness in the foot
  • Signs of arthritis or other structural problems

Weight-bearing X-rays may be recommended because they show how the bones and joints align while the foot is supporting the body. Additional imaging, such as magnetic resonance imaging (MRI), may be useful when the condition of the posterior tibial tendon or other soft tissues needs further evaluation.

An accurate diagnosis helps determine whether the flatfoot is flexible or rigid and whether the deformity is primarily related to tendon dysfunction, arthritis, injury, or another cause.

How Does Posterior Tibial Tendon Dysfunction Progress?

Adult-acquired flatfoot may progress through several phases. Early in the condition, the tendon may be inflamed or weakened, but the arch may still be maintained. As dysfunction progresses, the arch can collapse and the heel can move outward. Over time, the foot may become less flexible, and arthritis or significant deformity may develop.

The severity and flexibility of the deformity influence treatment. Early evaluation is important because nonsurgical care is generally most effective before the foot becomes rigid or substantial joint damage occurs.

What Treatments Are Available for Adult-Acquired Flatfoot?

Treatment depends on the severity of symptoms, the condition of the tendon, the flexibility of the foot, and whether arthritis or other deformity is present.

Nonsurgical Treatment

Many patients initially improve with a combination of conservative treatments, such as:

  • Supportive shoes with a firm heel counter
  • Over-the-counter or custom orthotics
  • An ankle-foot orthosis or other supportive brace
  • Temporary immobilization in a walking boot
  • Activity modification
  • Ice and elevation for swelling
  • Physical therapy
  • Exercises to improve calf flexibility, balance, and tendon function
  • Weight management when appropriate
  • Anti-inflammatory medication when recommended by a healthcare professional

Orthotics and braces may help support the arch and reduce stress on the posterior tibial tendon. Physical therapy can improve strength and flexibility, but exercises should be selected by a qualified professional because the appropriate program depends on the severity of the condition.

Surgical Treatment

Surgery may be considered when pain and functional limitations continue despite appropriate nonsurgical treatment or when significant deformity develops.

The specific procedure depends on the structures involved. Surgical treatment may include removing the diseased posterior tibial tendon and tendon transfer, lengthening a tight calf or Achilles tendon, realigning the heel or other bones, repairing supporting ligaments, or addressing arthritis in damaged joints.

The goals of surgery are to reduce pain, improve alignment, restore stability, and preserve or improve foot function. Not every patient requires surgery, and treatment should be individualized after a thorough examination and discussion of expected benefits and risks.

When Should You See a Foot and Ankle Specialist?

A low arch does not automatically require treatment. However, evaluation is recommended when you notice:

  • New or worsening pain along the inside of the ankle or arch
  • Swelling around the ankle
  • A recently flattened arch
  • A change in the position of the heel
  • Difficulty standing on one foot or rising onto the toes
  • Increasing difficulty walking or exercising
  • Foot or ankle symptoms that do not improve with rest and supportive shoes

Early assessment may help identify posterior tibial tendon dysfunction before the deformity becomes more difficult to manage.

Adult-Acquired Flatfoot Treatment at TSAOG Orthopaedics & Spine

Flat feet are not always painful, but a newly flattened or progressively changing arch in an adult may be a sign of posterior tibial tendon dysfunction. Prompt evaluation can help distinguish a stable, flexible flatfoot from a progressive collapsing foot deformity.

TSAOG’s Foot & Ankle specialists provide individualized care for adults and children with flatfoot conditions. Treatment recommendations are based on your symptoms, physical examination, imaging findings, activity level, and long-term goals.

If pain, swelling, changes in foot shape, or difficulty with daily activities are affecting you, schedule an appointment with TSAOG to learn more about your condition and treatment options.

This information is for educational purposes only and is not a substitute for professional medical evaluation or treatment.

References

What is Patellar Instability? Symptoms, Causes, and Treatment Options

Doctor testing a knee for stability

Reviewed By Jeffrey Shroff, M.D.

Patellar instability occurs when the kneecap repeatedly shifts, partially dislocates, or completely dislocates from its normal position within the groove at the front of the knee. At TSAOG, our Sports Medicine Center and comprehensive sports medicine doctors help patients identify the cause of knee instability and recommend treatment based on the severity of the injury and each patient’s activity level.

Patellar instability either develops as a result of a traumatic injury or sometimes because of differences in the shape or alignment of the knee that make the kneecap more likely to slip out of place. While some people experience only one episode, others develop recurring instability that affects sports participation, exercise, and everyday activities.

What is Patellar Instability and Why Does it Occur?

The patella, or kneecap, normally glides within a groove at the end of the thigh bone as the knee bends and straightens. Patellar instability occurs when the kneecap moves outside this groove, either partially or completely.

A patellar subluxation is a partial shift in which the kneecap moves out of position but returns on its own. A patellar dislocation occurs when the kneecap completely leaves its groove and often requires reduction to restore normal alignment. Patellar instability describes the broader condition that includes both recurrent subluxations and dislocations.

Several factors can contribute to patellar instability. A direct blow to the knee, sudden twisting movement, or awkward landing during sports may cause the kneecap to dislocate. Some people are also born with anatomical differences, such as a shallow groove for the kneecap, rotational or angular deformity of their legs or ligament laxity, that increase the likelihood of instability.

What are the Signs and Symptoms of Patellar Instability?

Symptoms vary depending on the severity of the injury and whether instability has occurred before. During an initial dislocation, patients often experience sudden pain, swelling, and difficulty bearing weight. Some describe feeling or seeing the kneecap shift out of place, then return to its normal position.

As instability becomes recurrent, symptoms may become less dramatic but more persistent. Patients commonly report a feeling that the kneecap is slipping, catching, or giving way during activities such as running, squatting, climbing stairs, or changing direction quickly. Ongoing swelling, tenderness around the kneecap, and reduced confidence in the knee are also common.

Some people experience only one episode of patellar instability, while others develop repeated episodes that interfere with sports, exercise, and everyday activities. Recurrent patellar instability can also increase the risk of cartilage damage within the knee joint, making early orthopedic evaluation important when the kneecap continues to shift out of place.

How Is Patellar Instability Diagnosed and Evaluated?

Diagnosis begins with a detailed discussion of how the injury occurred, previous episodes of instability, and current symptoms. A physical examination allows the physician to evaluate the kneecap movement, ligament stability, alignment, swelling, and range of motion.

Because patients sometimes confuse patellar instability with a knee dislocation, careful evaluation is important to determine which structures have been injured and whether additional damage has occurred.

Imaging studies often play an important role in diagnosis. Weight-bearing X-rays help evaluate bone alignment and identify fractures that may occur after a dislocation. MRI may be recommended to assess cartilage injuries, ligament damage, or other soft tissue structures that help stabilize the kneecap.

A thorough evaluation helps determine whether the injury represents a first-time dislocation or chronic instability, allowing treatment to be tailored to each patient’s condition.

What Treatment Options are Available for Patellar Instability?

Treatment depends on the severity of the injury, how often instability occurs, and whether damage to the surrounding cartilage or ligaments has developed.

For many first-time dislocations, conservative treatment is recommended. Rest, ice, bracing, activity modification, and physical therapy can help reduce pain while improving strength and stability around the knee. Rehabilitation focuses on restoring the range of motion, improving muscle control, and reducing the risk of future instability.

If you’re experiencing persistent knee pain or repeated instability, you may require additional evaluation to determine whether more advanced treatment is appropriate. When instability continues despite conservative care or repeated dislocations place the knee at risk for additional damage, surgical stabilization may be considered.

Surgical treatment is designed to restore normal kneecap tracking by repairing or reconstructing injured soft tissues, correcting underlying alignment problems, or addressing anatomical factors contributing to instability. The most appropriate procedure depends on the patient’s anatomy, activity level, and history of recurrent dislocations.

Schedule a Knee Evaluation With TSAOG Orthopaedics & Spine

A kneecap that repeatedly slips out of place is more than an inconvenience. Left untreated, recurrent instability can affect daily activities, limit athletic performance, and increase the risk of additional damage within the knee joint.

TSAOG’s Sports Medicine specialists provide comprehensive evaluation and treatment for patellar instability, helping patients return to work, sports, and everyday activities with greater confidence and stability.

If your kneecap feels unstable, repeatedly shifts out of place, or continues causing pain after an injury, book an appointment with TSAOG to learn more about your treatment options.

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