An Article By Cecilia Brennan, Podiatrist – New Step Podiatry.
Progressive Collapsing Foot Deformity: When a Lowering Arch is More Than Ageing
Have you noticed your foot getting flatter as you get older? Maybe your arch isn’t as high as it used to be. Perhaps your shoes fit differently, or you’ve noticed that one foot looks flatter than the other.
So, is this a normal part of getting older?
Our feet do change as we age, and some flattening can occur. But if your foot is becoming noticeably flatter over time, particularly if you are also developing pain or weakness, there may be more going on.
One possible cause is a condition called Progressive Collapsing Foot Deformity (PCFD).
It sounds complicated, but the name actually describes it quite well: the shape of the foot gradually changes and collapses over time.
What is Progressive Collapsing Foot Deformity?
PCFD is a condition where the structures that normally support and stabilise the foot gradually become less effective.
As this happens, the foot can slowly change shape and position.
The arch becoming lower is usually the most obvious change, but it’s only one part of what can happen.
You may also notice:
- the heel leaning further outwards
- the ankle appearing to roll inwards
- the front of the foot turning or drifting outwards
- the foot becoming wider
- one foot looking noticeably different from the other
These changes can develop gradually, which means people don’t always notice them straight away.
Some people first notice that their shoes are fitting differently. Others develop pain or swelling around the inside of the foot or ankle, difficulty walking longer distances, or a feeling that the foot is becoming weaker or less stable.
Why do we now Call it Progressive Collapsing Foot Deformity?
The way we understand this condition has changed considerably. For many years, an arch that became flatter during adulthood was commonly described as adult-acquired flatfoot.
Another medical term commonly used was Posterior Tibial Tendon Dysfunction (PTTD). The posterior tibial tendon runs behind the inside of the ankle and into the foot. It has an important job: it helps support the arch and control the foot when we stand and walk.
Because problems with this tendon were frequently seen alongside an increasingly flat foot, it was once thought that failure of the posterior tibial tendon was the main cause of the condition. We now know it’s not that simple. Not everyone with this type of foot collapse has posterior tibial tendon failure as the main problem. Other ligaments, tendons, muscles and joints can be involved, and different people can develop different combinations of changes.
One particularly important structure is the spring ligament. This ligament sits deep inside the foot and acts a little like a strong hammock, helping to support the arch. The spring ligament, posterior tibial tendon and several other structures work together to support and stabilise the foot. If one part becomes less effective, other structures may have to work harder to compensate. Over time, they too can become overloaded.
So rather than thinking of this condition as one damaged tendon causing a flat arch, we now understand it as a problem involving the support and alignment of the foot as a whole.
That’s why the newer term Progressive Collapsing Foot Deformity was introduced. It might be a mouthful, but the name actually describes the condition quite well:
Progressive – the changes can develop and worsen over time.
Collapsing – the structures supporting the foot are no longer maintaining its previous position.
Foot deformity – more than just the height of the arch can change. The position of the heel, front of the foot and, in some cases, the ankle can also be affected.
What Actually Supports Your Arch?
Your inside arch (medial longitudinal arch) isn’t held up by one tendon or ligament. Instead, think of it as being supported by a team. Some structures actively help control the foot as you move. These include muscles and tendons such as the posterior tibial tendon.
Others provide more passive support. These include:
- the spring ligament
- other ligaments around the foot and ankle
- the plantar fascia
- the joints of the foot
- the shape and position of the bones
The spring ligament is particularly important. It helps support one of the major bones forming the arch, the talus, and can be thought of somewhat like a hammock underneath it.
When these different structures work together, the foot is able to be flexible enough to adapt to the ground when we land, but then become firmer again when we push off to take our next step.
With PCFD, this system becomes less effective. Instead of the arch simply moving downwards, different sections of the foot begin moving out of their usual alignment. This is why PCFD is now considered a three-dimensional change in the foot, rather than simply a “fallen arch”.
But Don’t Feet Naturally get Flatter as we age?
They can. Our feet aren’t expected to look exactly the same at 70 as they did at 20. As we age, muscles can lose some strength and tendons and ligaments can change. Our feet may become a little longer or wider, and the arch can become somewhat lower. So seeing a lower arch doesn’t automatically mean you have PCFD.
There also isn’t one perfect arch height everyone should have. Some people naturally have very low arches their entire lives and never have any problems.
What we’re more interested in is whether your foot is progressively changing.
Things that may warrant a closer look include:
- one foot becoming noticeably flatter than the other
- your arch continuing to lower over time
- your heel or ankle changing position
- your foot becoming wider or changing shape
- new pain or swelling around the inside of the foot or ankle
- pain developing around the outside of the ankle
- difficulty walking or standing for as long as you previously could
- weakness when trying to rise onto your toes
So rather than asking only: “Do I have flat feet?” A more useful question can be: “Has the shape or function of my foot changed?”
Why Does Progressive Collapsing Foot Deformity Happen?
There isn’t always one single cause. PCFD is more commonly seen in middle-aged and older adults and develops when the structures supporting the foot are no longer able to adequately manage the forces being placed through them. Age can therefore be part of the picture, but it isn’t necessarily the whole explanation.
A number of factors may contribute, including:
- your natural foot shape and alignment
- previous injuries to the foot or ankle
- increased body weight
- inflammatory conditions
- changes in the quality of tendons and ligaments over time
- weakness or imbalance in the muscles controlling the foot
- tightness through the calf and Achilles
Often, it is likely to be a combination of factors rather than one single event.
Why can Progressive Collapsing Foot Deformity Become a Problem?
One of the most important things we assess with PCFD is whether the foot is still flexible. In the earlier stages, the foot may look quite flat when you’re standing on it, but the joints can still move and the foot can be brought back towards a better position. As PCFD progresses, however, the altered position of the foot places different stresses through the joints, tendons and ligaments.
Over time, the foot can become increasingly stiff. Eventually, the changed position can become fixed or rigid, meaning the foot can no longer easily be returned towards its previous alignment. Arthritis can also develop in affected joints as the condition becomes more advanced.
In some people, the changes can eventually extend as far as the ankle. This is why we don’t just look at how flat a foot is. We also look at where the change is occurring and whether the foot is still flexible.
How do we Classify Progressive Collapsing Foot Deformity?
There are a couple of different ways we can describe PCFD. The traditional system is useful for understanding how far the condition has progressed, while the newer PCFD classification helps us describe which parts of the foot are actually changing.
The traditional classification was developed when the condition was largely understood as Posterior Tibial Tendon Dysfunction. Although our understanding of PCFD has moved on, these stages can still be a useful way of describing the severity of the condition.
Stage I – Tendon symptoms without a change in foot shape: The posterior tibial tendon may be painful or irritated, but there isn’t yet a significant change in the shape or alignment of the foot.
Stage II – The foot has changed shape, but remains flexible: At this stage, the arch has started to lower and the position of the foot has changed, but importantly, the deformity is still flexible.
Stage III – The foot has become rigid: The changed position of the foot is now fixed or much more difficult to correct. Arthritis may also develop in some of the affected joints.
Stage IV – The ankle becomes involved: In more advanced cases, the changes extend beyond the foot and begin to affect the alignment and stability of the ankle.
One limitation of the traditional stages is that they suggest everyone follows a similar pathway from tendon problems through to increasing collapse. We now know PCFD doesn’t always behave that neatly. Different structures can be affected, and different parts of the foot can change independently or at the same time.
The newer PCFD classification therefore asks: Which parts of the foot are actually changing?
It divides the changes into five main areas:
- Class A – Heel: the heel increasingly leans outwards.
- Class B – Midfoot and forefoot: the front of the foot moves outwards.
- Class C – Arch and inner side of the foot: there is instability through the arch and inner side of the foot.
- Class D – Joints around the back of the foot: the joints around the talus shift out of their usual alignment.
- Class E – Ankle: the alignment and stability of the ankle are affected.
Importantly, you don’t have to fit neatly into just one class. Several different changes can occur in the same foot. Each area is also described as either flexible or rigid.
The two classification systems therefore give us slightly different information. The traditional stages give us a useful picture of severity and progression, particularly whether the foot remains flexible or has become rigid. The newer classification gives us a more detailed picture of where the changes are actually occurring. Together, they can help us understand an individual’s foot rather than simply describing it as “flat”. The classification systems help us Podiatrists determine the treatment plan.
How do we Assess Progressive Collapsing Foot Deformity?
Assessment starts by looking at your feet both sitting and standing.
We may look at:
- the height of your arch
- the position of your heel
- whether the front of your foot has moved outwards
- whether one foot looks different from the other
- where you have pain or tenderness
- the strength of the muscles and tendons supporting your foot
- your ability to perform a heel raise
- how flexible the foot and ankle are
- your calf and ankle flexibility
- how your foot moves when you walk
One of the key questions we’re trying to answer is whether the changes are still flexible or have become fixed.
In some cases, imaging can provide additional information. Weight-bearing X-rays allow us to assess how the bones and joints align while you’re standing. Ultrasound or MRI may be used to look more closely at soft tissues such as the posterior tibial tendon and spring ligament. More advanced imaging, including weight-bearing CT, can sometimes be useful because PCFD is a three-dimensional condition. Looking at the foot while it is actually carrying your body weight can provide information that isn’t always obvious on other forms of imaging.
How do we Manage Progressive Collapsing Foot Deformity?
There isn’t one treatment for every person with PCFD. This is particularly important now that we understand how many different structures and areas of the foot can be involved.
Management depends on:
- which parts of the foot are changing
- how much the foot has changed
- whether the changes are flexible or rigid
- which structures appear to be under stress
- where you are experiencing symptoms
- your activity levels
- your footwear
- your overall health and goals
Treatment may include footwear changes, activity modification, exercises, foot orthoses, bracing, shockwave therapy and medical laser.
Exercises may be used to improve the strength and control of the muscles supporting the foot and address contributing factors such as calf tightness.
Foot orthoses can provide additional support and help manage the forces travelling through the foot. When greater support is required, an ankle brace or ankle-foot orthosis may be considered.
The aim isn’t necessarily to create a perfectly shaped arch. Instead, treatment focuses on reducing symptoms, improving function, supporting the structures that are under stress and trying to limit further progression where possible.
If the deformity is significant, has become rigid, is associated with arthritis, or symptoms continue despite conservative treatment, referral to an orthopaedic foot and ankle surgeon or surgical podiatrist may be appropriate.
The Important Thing Isn’t how Flat Your Foot is – it’s Whether it’s Changing
Plenty of people have naturally flat feet and never need treatment. A foot that has always been flat is very different from a foot that used to have an arch and is progressively changing shape.
If you’ve noticed your arch becoming lower, your heel or ankle changing position, one foot looking different from the other, or you’re developing new pain or weakness, it’s worth having it assessed. It doesn’t necessarily mean you have Progressive Collapsing Foot Deformity. But understanding why your foot is changing, which parts of the foot are involved and whether those changes are still flexible can help determine whether it simply needs monitoring or whether it would benefit from additional support.
Noticed Your Foot or Arch Changing Shape?
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