Achilles Tendon Xanthoma

What Is An Achilles Tendon Xanthoma?

It’s a benign deposit of cholesterol-filled cells inside the Achilles tendon, the thick tendon joining the calf muscles to the heel bone. It shows up as a firm lump or a general thickening of the tendon, and it isn’t cancer.

The Achilles tendon is the most common site for tendon xanthomas. They form when LDL cholesterol from the blood enters the tendon, becomes oxidized, and is taken up by immune cells called macrophages, which fill with fat and build up into the lesion.^[3] Because the fat sits inside the tendon itself, the lump moves with the tendon and feels firm rather than soft.

Achilles tendon xanthomas belong to the wider family of xanthomas, fatty deposits that can form in the skin, tendons and elsewhere. Our guides to xanthomas and tendon xanthomas cover the family, and xanthoma of the Achilles tendon looks at the same condition from another angle.

Why Is An Achilles Tendon Xanthoma Linked To Familial Hypercholesterolemia?

Because familial hypercholesterolemia keeps LDL cholesterol very high from birth, and years of high LDL drive cholesterol into the tendons. Tendon xanthomas are one of its classic physical signs.

Familial hypercholesterolemia (FH) is an inherited condition in which the body can’t clear LDL cholesterol properly. It affects about 1 in 250 to 1 in 500 people, and it’s passed on in a dominant way, so each child of an affected parent has a 50% chance of inheriting it. Tendon xanthomas on the Achilles tendons, elbows, hands, knees and feet are among its typical signs, along with xanthelasma on the eyelids.^[1]

That’s why an Achilles tendon xanthoma is taken seriously. Without medical care, about half of men with FH had a coronary event by age 50, and about 30% of women by 60.^[1] Finding the lump can be the first clue that leads to a diagnosis and to care that protects the heart. Tendon xanthomas can occasionally occur with other conditions too, which are covered below.^[3]

How Common Are Achilles Tendon Xanthomas In Familial Hypercholesterolemia?

Fairly common. Research suggests about a third of people with heterozygous familial hypercholesterolemia have tendon xanthomas that can be felt or seen, and about 40% of adults have them when ultrasound is used.

A 2024 study of 377 people with genetically confirmed FH measured the thickness of the Achilles tendon by ultrasound. The median maximum thickness was 5.5 mm, ranging from about 3.4 to 16.6 mm. Thicker tendons were independently linked to older age, male sex, higher LDL cholesterol and higher lipoprotein(a), a blood fat particle that is largely inherited.^[2]

Interestingly, those four factors explained only about a fifth of the variation, so some people with FH develop large tendon xanthomas while others with similar cholesterol don’t. The type of gene change didn’t seem to explain the difference either.^[2] In short, the absence of a lump doesn’t rule out FH, and its presence is a strong reason to test.

What Does An Achilles Tendon Xanthoma Look And Feel Like?

Usually a firm, smooth thickening or nodule along the back of the heel, often on both legs. It moves with the tendon, is often painless, and the skin over it usually looks normal rather than yellow.

Unlike eyelid xanthelasma, which sits in the skin and looks yellow, an Achilles tendon xanthoma is inside the tendon, so you mainly notice it by feel or by the shape of the back of your ankle. Signs include:

• A thicker-looking tendon. The back of the ankle looks fuller or lumpier than usual.
• A firm nodule. One or more firm, smooth lumps along the tendon.
• Both sides. Often both Achilles tendons are affected.
• Other tendons. Similar lumps over the knuckles, elbows or knees can appear too.^[1]

Early xanthomas can be subtle and are sometimes found only on ultrasound.^[2] Our guides to tendon xanthoma and xanthoma tendon show where else they form.

Can An Achilles Tendon Xanthoma Cause Pain Or Tendon Problems?

It can. Many are painless, but people with high cholesterol appear more prone to tendon injury and slower healing, and a large xanthoma can rub on footwear or make the tendon stiffer.

A review of tendon problems in high cholesterol and FH concluded that people with hypercholesterolemia are more prone to tendon injury and impaired healing. Inflammatory signals and enzymes that break down tendon tissue are thought to make tendons stiffer, though the exact mechanisms aren’t fully understood.^[4]

Read moreXanthoma Achilles Tendon

In everyday terms, some people notice aching at the back of the heel after activity, discomfort from shoe backs, or episodes that feel like tendinitis. Any new pain, swelling or a sudden “snap” at the back of the ankle needs prompt medical attention, whatever the cause.

How Is An Achilles Tendon Xanthoma Diagnosed?

With an examination, a family history, a fasting lipid profile and, usually, an ultrasound of the tendon. Genetic testing can confirm familial hypercholesterolemia, and lipoprotein(a) is worth measuring too.

1. Examination. The doctor feels both Achilles tendons and checks other tendons and the eyelids.
2. Family history. High cholesterol, early heart attacks or strokes in close relatives point toward FH.^[1]
3. Lipid profile. A blood test for total cholesterol, LDL, HDL and triglycerides.
4. Ultrasound. The method of choice in everyday practice to confirm and measure tendon xanthomas.^[3]
5. Lipoprotein(a). Linked with thicker tendons in FH and worth checking.^[2]
6. Genetic testing. Can confirm FH and helps when testing relatives.^[1]

MRI is sometimes used when the picture is unclear, for example to look at the rest of the tendon. If the results don’t fit FH, other causes are considered.

What Else Can Cause Achilles Tendon Xanthomas?

FH is the most common cause, but tendon xanthomas can occur with other lipid conditions. A rare inherited one is cerebrotendinous xanthomatosis, which can cause tendon xanthomas even with normal cholesterol.

Cerebrotendinous xanthomatosis (CTX) is a rare inherited disorder of bile acid production. Its pattern is distinctive: diarrhea in infancy, cataracts in childhood in about 75% of people, tendon xanthomas in the teens or twenties, and nerve and brain problems in adulthood. Early care with a bile acid called chenodeoxycholic acid appears to prevent symptoms, which is why recognizing it early matters.^[5]

A young person with Achilles lumps and normal cholesterol, or with a history of childhood cataracts, should be checked for CTX. Our guide to xanthomatosis covers widespread and inherited xanthomas, and tuberous xanthoma covers lumps over the elbows and knees.

How Is An Achilles Tendon Xanthoma Managed?

By lowering LDL cholesterol, which is the main cause. Statins are the first-line medicine for FH, with other options such as LDL apheresis for severe cases. Surgery on the tendon is rarely needed.

Because the lump is driven by high LDL, management targets the cholesterol rather than the lump. Statins are the first-line approach for FH, alongside a heart-healthy diet, activity and not smoking.^[1] For people whose cholesterol stays very high, approaches such as LDL apheresis, which filters LDL out of the blood, have also been used.^[3]

Will the lump shrink? Lowering LDL can help, but the effect of statins on tendon changes isn’t fully clear, and established xanthomas may not disappear.^[4] Doctors are cautious about operating on the Achilles because it’s a weight-bearing tendon, so surgery is usually kept for large, painful lumps that affect walking. This is always doctor-led care; creams and home remedies have no role. For an overview, see our guide to managing xanthomas.

What Does An Achilles Tendon Xanthoma Mean For Your Heart?

It’s a warning sign worth acting on. FH without medical care carries a high risk of early heart disease, and tendon xanthomas have been linked to about three times the risk of premature coronary heart disease in people with FH.

Without medical care, about half of men with FH had a coronary event by 50 and about 30% of women by 60.^[1] Researchers have linked tendon xanthomas to roughly a threefold higher risk of premature coronary heart disease in FH, though that link weakens once LDL cholesterol and other risk factors are taken into account.^[2] In the 2024 study, people who’d already had heart or artery disease tended to have thicker tendons.^[2]

The positive side is that FH responds well to early care. Finding an Achilles tendon xanthoma can be what prompts the diagnosis and the cholesterol-lowering that protects your heart for decades.^[1]

What Does An Achilles Tendon Xanthoma Mean For Your Family?

If it’s caused by FH, your parents, brothers, sisters and children may have it too. Each child of an affected parent has a 50% chance of inheriting FH, so doctors often recommend testing close relatives.

Because FH is passed on in a dominant way, finding it in one person often uncovers it in others.^[1] Testing relatives, sometimes called cascade screening, means they can start cholesterol-lowering early too, before any heart problems develop. Genetic testing makes this simpler once the family’s gene change is known.^[1]

Children with FH can start care young, which is why diagnosis in a parent matters so much. Our guide on whether xanthelasma is genetic covers the family side of the eyelid type too.

When Should You See A Doctor About An Achilles Tendon Lump?

Always. Any firm lump or thickening in the Achilles tendon deserves a doctor’s assessment and a cholesterol test, and sudden pain or a snapping feeling needs urgent attention.

Read moreWhat's Xanthelasma

Your family doctor can start the tests and refer you to a lipid clinic if FH is suspected. Our guides to xanthoma of the Achilles tendon and tendon xanthomata have more.

What If You Were Looking For The Eyelid Type?

Yellow plaques on the eyelids are xanthelasma, a different and usually simpler matter. It’s the most common type of xanthoma, and about half of people with it have a blood fat disorder, so a cholesterol check is still worthwhile.

Xanthelasma affects around 1.1% of women and 0.3% of men and sits in the eyelid skin rather than a tendon.^[6] It can also be a sign of FH, so if you have both eyelid plaques and tendon lumps, mention both to your doctor. Our main guide to xanthelasma covers the eyelid type, and xanthoma explains how all the types fit together.

What’s The Bottom Line On Achilles Tendon Xanthoma?

An Achilles tendon xanthoma is a benign cholesterol deposit in the heel tendon, but it’s a classic sign of familial hypercholesterolemia, which raises the risk of early heart disease and runs in families. See a doctor for a lipid test and, usually, an ultrasound.

The lump itself is rarely the problem; the cholesterol behind it is. Early diagnosis, cholesterol-lowering care and testing your relatives make a real difference. If you were looking for yellow plaques on the eyelids instead, see our xanthelasma guide, and browse all our xanthelasma guides.

Common Questions About Achilles Tendon Xanthoma

Read Next

Tendon XanthomasEvery tendon site Xanthoma Of Achilles TendonAnother angle XanthomataWhat each type means XanthomasThe whole family XanthomatosisWidespread xanthomas XanthelasmaThe eyelid type