Flat Feet & Arch Pain: The Tibialis Posterior Connection
When people notice that their arch appears lower on one foot or that their foot seems to be “collapsing,” they often assume that flat feet are the way they were built. In reality, a previously normal arch can gradually flatten over time due to weakness or injury of an important muscle and tendon known as the tibialis posterior.
The tibialis posterior muscle originates deep within the calf and attaches to several bones on the inside of the foot. Every time you walk, run, jump, change direction, or push off the ground, this muscle works to stabilize the foot and support the arch. Many people are surprised to learn that the arch is not held up by ligaments alone. While ligaments contribute to stability, the arch relies heavily on active muscular support. The tibialis posterior acts like a dynamic suspension system, helping the foot absorb force, control motion, and efficiently transfer energy up the leg.
When the tendon becomes overloaded from something like running, sports participation, prolonged standing, weight gain, footwear changes, or years of accumulated stress, it can weaken. As this occurs, the arch may gradually lose support and flatten. For some people, this process happens slowly over several years. Others may notice a relatively rapid change in their foot shape following a period of increased activity or injury.
Why It Is Frequently Mistaken for Other Conditions
One of the reasons posterior tibial tendon dysfunction is commonly overlooked is that the symptoms often mimic several other foot and ankle conditions.
Patients frequently describe pain along the inside of the ankle, pain underneath the arch, heel pain when walking, shin discomfort during running, swelling around the inside ankle bone, foot fatigue after prolonged standing, difficulty walking long distances, and a feeling that the foot is becoming weaker. Because these symptoms overlap with other diagnoses, patients are often told they have plantar fasciitis, shin splints, achilles tendonitis, a strain in the foot, arthritis, or normal “flat feet.” The underlying issue may be a tendon that is gradually losing its ability to support the foot.
A common story we hear in the clinic is that someone has been stretching their plantar fascia, rolling their foot on a ball, or purchasing increasingly supportive shoes for months without significant improvement. When we examine the foot more closely, weakness of the tibialis posterior is often a major contributor.
Why the Foot Matters to the Rest of the Body
The foot is the foundation of the entire lower extremity. When the arch begins to collapse excessively, the mechanics of the ankle, knee, hip, and even lower back can change. As the foot rolls inward, the shin tends to rotate inward as well. This can change the way the knee feels during activity and may place additional stress on structures throughout the leg. For this reason, individuals with significant arch collapse may experience recurrent shin splints, patellofemoral pain syndrome (runner’s knee), IT band irritation, achilles tendon problems, calf tightness, hip pain, or lower back pain.
This does not mean that flat feet automatically cause these conditions. However, poor foot mechanics can be one contributing factor within a much larger movement system. That is why a comprehensive assessment should never focus solely on the foot. Evaluating strength, balance, mobility, gait mechanics, and overall movement patterns often provides a clearer picture of why symptoms developed in the first place.
The Four Stages of Posterior Tibial Tendon Dysfunction
Like many tendon-related conditions, posterior tibial tendon dysfunction tends to progress gradually rather than appearing overnight.
Stage 1: Tendon Irritation and Early Pain
The tendon becomes inflamed or irritated, but the overall structure of the foot remains relatively normal. Patients commonly experience mild pain on the inside of the ankle, discomfort after exercise, morning stiffness, and tenderness along the tendon. At this stage, the condition often responds well to conservative treatment.
Stage 2: Early Arch Collapse
As the tendon weakens, the arch loses support. Patients may notice a visibly flatter foot, increased inward rolling of the ankle, difficulty balancing on one leg, reduced calf strength, and difficulty performing a single-leg heel raise. This is often the stage at which people first realize something more significant is occurring.
Stage 3: Progressive Flatfoot Deformity
The flattening becomes more pronounced and the foot starts to stiffen. Symptoms may include ongoing pain during walking, reduced walking tolerance, difficulty participating in sports, noticeable changes in foot shape, and increased reliance on supportive footwear.
Stage 4: Advanced Dysfunction
In advanced cases, the deformity can affect the ankle joint itself. At this point, patients may experience significant stiffness, pain, inflammation, and difficulty walking. Fortunately, most individuals seek help long before reaching this stage.
Strength Is Often the Missing Piece
Perhaps the biggest misconception surrounding flat feet is that support alone will solve the problem. While supportive footwear and orthotics can be helpful, they do not replace strength. Imagine wearing a sling for a weak shoulder forever without ever strengthening the muscles. The shoulder might feel supported, but the underlying weakness would remain. The same principle applies to the foot. The goal of rehabilitation is not to prop up the arch. It is to improve the capacity of the muscles and tendons responsible for supporting it.
Single-Leg Heel Raises
Single-leg heel raises remain one of the most effective exercises for assessing and strengthening the tibialis posterior. A healthy tendon should allow an individual to repeatedly rise onto their toes while maintaining good control and balance. Difficulty performing this movement is often an early indicator of dysfunction.
Foot Doming (Short Foot Exercise)
The foot doming exercise teaches patients to activate the intrinsic muscles of the foot. Rather than gripping with the toes, the goal is to gently shorten the foot and elevate the arch through muscular control. Although the movement appears straightforward, it can be surprisingly challenging for individuals who have relied on passive support for years.
Eccentric Calf Strengthening
By slowly lowering through the calf raise movement, the tendon is exposed to controlled loading that helps stimulate adaptation and improve its ability to tolerate activity. Over time, this can improve strength, endurance, and resilience.
When Orthotics, Shockwave Therapy, and Laser Therapy Can Help
Although exercise is often the foundation of treatment, additional therapies may help reduce symptoms and accelerate recovery.
Orthotics
Orthotics can reduce stress on irritated tissues and improve comfort during daily activities. For some patients, an over-the-counter insert is sufficient. Others may benefit from a custom orthotic depending on the severity of the collapse and their activity demands. Importantly, orthotics should be viewed as a tool rather than a cure.
Shockwave Therapy
Shockwave therapy has become increasingly popular in the treatment of chronic tendon conditions. The treatment delivers mechanical energy into the affected tissue, which may stimulate healing responses and help reduce persistent pain. Shockwave therapy is often considered when symptoms have been present for several months or have not responded adequately to exercise alone.
Laser Therapy
Laser therapy may be used as part of a broader rehabilitation program to help reduce pain and support tissue recovery. While it should not replace strengthening, it can be a useful adjunct for some patients during the early stages of rehabilitation.
The Bottom Line
Not all flat feet are a matter of genetics or foot structure. In many cases, a painful or progressively collapsing arch may be related to dysfunction of the tibialis posterior tendon, the primary muscular support system of the arch. The earlier this condition is identified, the easier it is to manage. Waiting until the arch has significantly collapsed often makes treatment more complicated and recovery more prolonged.
If you are experiencing arch pain, inner ankle pain, recurring plantar fasciitis symptoms, chronic shin splints, or a noticeable change in your foot shape, it may be worthwhile to undergo a professional assessment. Often, the solution is not finding a more supportive shoe. It is identifying why the arch is struggling in the first place and restoring the strength, control, and function needed to keep you active for years to come.
Frequently Asked Questions Flat Feet
Can flat feet develop in adults who didn’t have them as children?
Yes. Adult-acquired flatfoot is most often related to dysfunction of the tibialis posterior tendon, which can gradually lose its ability to support the arch over time. People who had a normal arch for most of their life can notice their foot shape changing in their 40s, 50s, or beyond.
How do I know if my arch pain is the tibialis posterior or something else?
The distinguishing feature is usually pain along the inside of the ankle and underneath the arch, often combined with difficulty performing a single-leg heel raise on the affected side. Plantar fasciitis tends to cause sharp heel pain with the first few steps in the morning, while tibialis posterior dysfunction tends to worsen with prolonged standing or activity. An in-person assessment is the best way to confirm which structure is involved.
Will arch supports or orthotics fix the problem on their own?
Orthotics can reduce stress on the tendon and improve day-to-day comfort, but they do not strengthen the muscles responsible for supporting the arch. Most people benefit from combining supportive footwear or orthotics with a progressive strengthening program targeting the tibialis posterior, intrinsic foot muscles, and calf.
How long does it take to recover from posterior tibial tendon dysfunction?
Recovery depends on the stage at which the condition is identified. Early-stage cases caught in the irritation phase often improve within several weeks of focused rehabilitation. More advanced cases with significant arch collapse can take several months and may require a combination of strengthening, orthotic support, and additional therapies. Catching it early makes a meaningful difference.
Should I stop running or exercising if I have this condition?
Not necessarily. Total rest is rarely the answer for tendon-related conditions. Modifying load, adjusting the type of activity, and introducing targeted strengthening is usually more effective than stopping altogether. A clinician can help guide which activities to scale back and which to continue safely.
Questions about this article? Sore feet? Give us a call, we can help.
