Plantar Fasciitis vs Achilles Tendonitis – Similarities and Differences

Got pain in your feet? Specifically in your heel? You’re most likely wondering if you have plantar fasciitis vs Achilles tendonitis.

The two conditions have some overlapping symptoms, so it may be difficult to figure it out. This article aims to eliminate that confusion and help you clearly identify the difference.

First, we’ll give an overview of each condition, including what it is and its symptoms. Then, we’ll compare the common symptoms and explain how to figure out which one is the cause of your foot pain.

What Is Plantar Fasciitis?

Plantar fasciitis is an inflammatory condition that affects the plantar fascia—the thick band of tissue that runs underneath your foot, from your heel to just underneath your toes.

This band of tissue serves the purpose of shaping the arch and holding the foot bones in place, it also provides some shock absorption on every step.

When this strip becomes inflamed, it’s called plantar fasciitis. This can happen for a variety of reasons, including overuse, overstretching, or an injury that occurs to the underside of the foot.

Symptoms of Plantar Fasciitis

These are the most common symptoms associated with plantar fasciitis. In most cases, you will experience most, if not all of them when you have the condition.

Swelling In the Heel

You’ll probably notice the inflammation in your heel first, as it swells slightly. There’s not a lot of swelling in the rest of the foot, due to the foot’s structure, but it’s likely to be noticeable in your heel.

Pain In the Heel

Along with minor swelling, you’re likely to have pain underneath your heel that occurs mostly after rest—that is, first thing in the morning or when standing after being seated for a lengthy period.

This happens because the plantar fascia tenses up when it’s not in use, like a muscle after a gym session. When it’s stretched out again, it can often lead to micro-tears in the tissue, which increases the pain.

You may notice a dull ache in the heel throughout the day. But the sharp, shooting morning pain or pain after rest is the telltale sign of plantar fasciitis. The pain may actually diminish slightly when you exercise and stretch the foot.

Pain In the Arch

Although it won’t be as sharp and noticeable as the pain in your heel, you may also experience pain in the arch of your foot.

This is because the tissue is inflamed from heel to toe and its shock-absorbing properties are compromised. This can leave you sore as impact takes its toll.

It can also occur because of micro-tears that happen in the arch when stretching the plantar fascia after it’s been at rest.

Most often, pain in the arch occurs later in the day, after you’ve been on your feet for some time.

Tightness In the Achilles Tendon

The Achilles tendon connects to the plantar fascia at the heel. When the plantar fascia is tight, it can put strain on the Achilles tendon as well.

This is one of the reasons it can be so difficult to distinguish which condition you have!

Less Pain During Exercise

While you’re exercising, the pain in your plantar fascia may improve, provided you’re wearing shoes that offer arch support.

However, your plantar fascia may begin to ache after exercise, if micro-tears have occurred during the activity.

What Is Achilles Tendonitis?

Achilles tendonitis is inflammation of the Achilles tendon—the thick, strong tendon that connects your lower calf muscle to your heel.

This tendon works with the calf muscle to help you perform movements that involve the bending of your feet at the ankle, like running or jumping.

Achilles tendonitis—also called tendinopathy—most commonly caused by overuse of the tendon, usually during exercise that places strain on that particular part of the body.

As such, those who are active and partake in activities that involve a significant load on the Achilles tendon—runners, walkers, athletes—are at a higher risk of developing this condition.

It can also occur when the tendon begins to degenerate, which can happen as a result of an injury or simply as we age.

Symptoms of Achilles Tendonitis

Here are some of the common symptoms of Achilles tendonitis to consider. Some of them are quite similar to plantar fasciitis, but others are quite different.

Swelling In the Back Of the Heel

You may notice inflammation—swelling—either at the back of your heel or at either side of your heel, above your ankle bones.

The swelling may get worse throughout the day. You may also notice redness and warmth in the area, which is a sign of inflammation.

Thickening of the tendon may also occur, so you could have a lump or misshapen mass at the back of your heel even when the swelling has gone down.

Pain In the Back Of the Heel

As well as swelling in the back of your heel, you may feel pain in this area as well. It may be a burning, stretching, or aching pain.

This pain could extend from the heel into the calf muscle, especially when walking or running. It could also be tender to the touch, or feel more painful at the back of the heel when you have your shoes on.

Pain In the Arch

As the Achilles tendon tightens, it can place strain on the plantar fascia as they meet at the heel bone. This may cause the plantar fascia to tense, leading to pain in the arch.

Stiffness In the Morning

Your lower legs—from calf to heel—may feel stiff in the morning or after inactivity. This should improve as your muscles warm up and you begin to do your everyday activities.

Tight Calf Muscles

Although the stiffness will most likely improve, you may still have tight calf muscles throughout the day.

Inflammation in the Achilles tendon may cause the tendon to shorten, which can place strain on the calf muscle, leading to tightness and irritation.

Restricted Range of Motion

Tight calf muscles and inflammation may lead to restricted range of motion in the foot. You may find that you’re unable to flex your heel—lift your toes in the air or stand up on your toes—or that you can do the action but not without pain.

Increased Pain During and After Exercise

Activity that involves the legs and feet—walking, running, jumping, squatting, and more—will cause the pain to increase.

You may feel it during your activity and the pain and stiffness may worsen after your activity. Even non-exercise activities like climbing stairs may aggravate your Achilles tendon and cause the pain to flare up.

What Are Common Symptoms of Both Conditions?

Symptoms that are common to both plantar fasciitis and Achilles tendonitis include:

  • Swelling in the heel area
  • Pain in the heel area in the morning
  • Pain in the arch area
  • Tightness in the Achilles tendon

However, the differences are significant enough to differentiate which condition is causing your pain.

How Do I Know Which Condition I Have?

Consider these factors to determine if your foot pain is plantar fasciitis vs Achilles tendonitis. An accurate diagnosis is essential in order to figure out how best to treat your foot condition!

Pain Location

Where in the heel do you experience the pain? This is a telltale sign of each condition.

Pain underneath your heel—on or inside the pad that you step onto—is a sign that your condition is most likely plantar fasciitis.

However, if your pain is in the back of your heel—not underneath your foot—and extends into your lower calf, then it’s indicative of Achilles tendonitis.

When Pain Occurs

Another important factor that can distinguish one condition from the other is when the pain occurs.

You have plantar fasciitis if you feel sharp, shooting pain in your heel in the morning, when you get out of bed, or when getting back on your feet after sitting or lying down for an extended period.

On the other hand, pain that remains relatively mild and can go unnoticed until you get active—during and after exercise—is more likely to be Achilles tendonitis.

Remember to pair the “when” with the “where” for the most accurate diagnosis!

Response to Activity

Plantar fasciitis, apart from flaring up when first becoming active after being at rest, tends to improve during activity.

If you wear supportive shoes and walk often during the day, you may notice that your feet feel fine. It’s far more likely to occur when you haven’t been active.

Achilles tendonitis tends to feel fine while you’re resting but worsen with more strenuous activity. For example, you can feel great while you’re walking around the office, but start to feel aching in your lower leg and heel 5 minutes into your evening run.

Quick Summary

Here’s a quick checklist of symptoms so you can finally nail down whether you have plantar fasciitis vs Achilles tendonitis!

Plantar Fasciitis

  • Pain and swelling underneath the heel
  • Sharp, shooting pain in the morning or after rest
  • Tightness in the Achilles/calf
  • Arch pain (sometimes)
  • Pain improves with exercise

Achilles Tendonitis

  • Pain and swelling at the back of the heel
  • Stiffness in the morning
  • Tightness in the Achilles/calf
  • Arch pain (sometimes)
  • Pain worsens with exercise

Ackermann, P. W., Phisitkul, P., & Pearce, C. J. (2022). Achilles tendinopathy – pathophysiology: state of the art. Journal of ISAKOS: Joint Disorders & Orthopaedic Sports Medicine, 3(5), 304–314. 

Latt, L. D., Jaffe, D. E., Tang, Y., & Taljanovic, M. S. (2020). Evaluation and Treatment of Chronic Plantar Fasciitis. Foot & Ankle Orthopaedics, 5(1), 247301141989676. 

Medina, M. A., & Usker Naqvi. (2019, April 8). Achilles Tendonitis.; StatPearls Publishing.