Lump in Leg: Causes and When to Worry

What a leg lump can be

A lump in the leg can start in any layer. Where it sits and how it feels are the best early clues.

Common harmless causes of a lump on the leg

Lipoma

A lipoma is a slow-growing lump of fat cells. It feels soft and doughy, moves easily under the skin and is painless. Lipomas are common on the thigh. They are benign and only need removing if they bother you, grow quickly or are larger than about 5 cm, when an ultrasound or MRI is used to make sure it is not a fatty tumor of another kind.

Epidermoid and sebaceous cysts

These are small, round, firm bumps in the skin, often with a dark central dot (punctum). They can become red and painful if they rupture or get infected. Squeezing makes inflammation worse. Many people call them a sebaceous cyst.

Hematoma after an injury

A knock to the thigh or shin can leave a pocket of blood, a hematoma, that feels like a firm lump under a bruise. It usually softens and shrinks over 2 to 6 weeks. On the shin, where skin is thin, it can take longer. A deep thigh bruise that turns hard and painful weeks later may be myositis ossificans, where bone forms in the injured muscle. A hematoma with no injury, or one that keeps growing, needs checking.

Varicose veins and thrombophlebitis

Varicose veins are twisted, bulging veins, usually on the calf or inner thigh, that look worse after standing and flatten when you lie down. If a vein suddenly becomes a hard, red, tender cord, that is superficial thrombophlebitis (an inflamed vein with a small clot). It is usually managed with warm compresses and anti-inflammatories, but it can sit near a deeper clot, so an ultrasound is often advised.

Baker's cyst behind the knee

A Baker's cyst is a fluid-filled swelling in the hollow behind the knee. It is linked to arthritis or a cartilage tear and feels tight when the knee is straight. If it bursts, fluid tracks into the calf and causes pain and swelling that look exactly like a deep vein thrombosis, so an ultrasound is needed to tell them apart.

Insect bites, ingrown hairs and folliculitis

Small itchy or tender bumps on the shins and thighs are often bites or inflamed hair follicles, especially after shaving or waxing. They settle within days.

Muscle hernia

A bulge on the front or outer shin that appears when you stand or tense the muscle and disappears when relaxed is often a muscle hernia: muscle pushing through a small gap in its covering (fascia). It is harmless unless painful.

Causes that need prompt attention

Deep vein thrombosis

A deep vein thrombosis (DVT) is a clot in a deep leg vein. It causes swelling of the whole calf or leg rather than a discrete lump, along with aching, warmth and sometimes redness. Risk is higher after surgery, long flights, pregnancy, cancer, hormone pills and immobility. A clot can travel to the lungs, so same-day assessment is needed.

Abscess and cellulitis

An abscess is a collection of pus that forms a hot, red, painful, often fluctuant (squishy) lump. It may come to a head and drain. Spreading redness around it suggests cellulitis. Large abscesses need draining by a clinician. Recurrent abscesses on the legs and buttocks are common with MRSA.

Swollen lymph nodes in the groin

Lymph nodes in the upper inner thigh swell with infections of the leg, foot or genitals. Nodes that are hard, painless, fixed, larger than 1.5 to 2 cm or present for more than 2 to 3 weeks without a cause need assessment for lymphoma or spread of cancer.

Soft tissue sarcoma

Soft tissue sarcoma is a rare cancer of fat, muscle or connective tissue, and the thigh is the single most common site. It usually starts as a painless lump that grows over weeks or months. NICE advises an urgent ultrasound for any adult with an unexplained lump that is increasing in size. Features that raise concern:

• larger than 5 cm (about a golf ball)
• deep to the fascia, so it does not move freely and becomes fixed when the muscle is tensed
• growing
• painful, or recurring after a previous removal

Most lumps with one of these features still turn out benign. Scanning is how you find the rare one that is not.

Bone lumps

A hard lump fixed to the bone is often an osteochondroma, a benign bony outgrowth near the knee in teenagers and young adults. Bone pain that is deep, constant and worse at night, with or without a lump, needs an X-ray to rule out a bone tumor such as osteosarcoma, which peaks in adolescence.

Skin cancer

Melanoma is common on the legs, especially in women. A mole that is new, changing, irregular in shape or color, or bleeding needs checking. Nodular melanoma and squamous cell carcinoma can appear as a firm, growing bump.

Lump on leg by location

Thigh

Lipomas, hematomas, sebaceous cysts and sarcomas are the main thigh lumps. A lump in the crease of the upper thigh may be a lymph node or a femoral or inguinal hernia, which bulges when you cough. See groin mass for those.

Behind or around the knee

A Baker's cyst is the usual cause behind the knee. A soft swelling on the front of the kneecap is prepatellar bursitis. A pulsing lump behind the knee may be a popliteal artery aneurysm. More detail is on the knee lump page.

Shin

The shin has little padding, so knocks produce obvious lumps and bruises. Tender red nodules on both shins, often with fever or joint aches, suggest erythema nodosum, an inflammatory reaction to infections, medicines, pregnancy, sarcoidosis or bowel disease.

Calf

Calf lumps include varicose veins, thrombophlebitis, a ruptured Baker's cyst, muscle tears and lipomas. A whole calf that is swollen and tender is a DVT until proven otherwise.

Accompanying symptoms and what they suggest

When to worry about a lump in the leg

See a doctor promptly for any lump that is growing, hard, deep, fixed, painful without injury, or larger than 5 cm, and for any lump that has not settled after 2 to 3 weeks. Seek same-day care for a swollen, painful calf or a hot, spreading red lump.

How doctors diagnose a leg lump

Your doctor will ask:

• how long it has been there and whether it is growing
• whether it followed an injury, bite or infection
• whether it hurts, changes with standing or muscle tension, or comes and goes
• about fever, night sweats, weight loss, recent travel, surgery, pregnancy or hormone use

They will measure the lump, check whether it moves, whether it is in the skin or deeper, and examine the groin nodes and the circulation in the leg.

Tests depend on what they find:

• Ultrasound: the first test for most lumps. It shows whether the lump is solid or fluid and checks veins for a clot.
• D-dimer blood test and venous ultrasound: for suspected DVT.
• X-ray: for lumps on bone.
• MRI: for deep, large or uncertain lumps, before any biopsy.
• Biopsy: a core needle biopsy, ideally at a specialist sarcoma center, when cancer is possible. Removing a suspicious lump without a plan can make later cancer surgery harder.

Treatment depends on the cause

• Lipomas and cysts: often left alone. Removal under local anesthetic if painful, growing or bothersome. Inflamed cysts may need draining first.
• Hematoma: rest, ice for 15 to 20 minutes at a time in the first 48 hours, compression and elevation. Large ones may be drained.
• Abscess: incision and drainage, sometimes with antibiotics.
• Varicose veins: compression stockings, then options such as endovenous ablation or sclerotherapy.
• DVT: blood-thinning (anticoagulant) medicine, usually for at least 3 months.
• Baker's cyst: treat the knee problem behind it. Drainage or a steroid injection can ease symptoms.
• Sarcoma and bone tumors: specialist surgery, often with radiotherapy or chemotherapy.

Home care while you wait to be seen

For a lump that followed a knock or bite, rest, ice and elevation help, and acetaminophen (paracetamol) or ibuprofen can ease pain (follow the label dose). Do not squeeze or try to drain a lump. Take a photo and measure it with a ruler so you can tell whether it is changing.

Frequently asked questions

What causes a lump in the leg?

Most leg lumps are lipomas, skin cysts, hardened bruises, varicose veins, Baker's cysts or bites. Less often they are abscesses, swollen lymph nodes, blood clots or tumors. The lump's depth, texture, growth and any injury beforehand are the best clues to which.

When should I worry about a lump on my leg?

Worry if the lump is hard, deep, fixed, growing, painful without injury or larger than 5 cm (2 inches). Also seek prompt care for a swollen, hot, painful calf or a red lump with fever. These need a scan or same-day assessment.

Can a leg lump be cancer?

Rarely. Soft tissue sarcomas most often appear in the thigh as a painless, growing, deep lump. Skin cancers and lymphoma can also cause leg or groin lumps. An ultrasound or MRI tells most benign lumps apart from those that need a biopsy.

Is a lump in the calf a blood clot?

A clot usually causes swelling of the whole calf, warmth and aching rather than a small separate lump. A hard, tender cord along a surface vein is thrombophlebitis. Either needs a same-day check, usually with an ultrasound scan.

Why do I have a hard lump on my shin after hitting it?

That is usually a hematoma, a pocket of clotted blood under the skin. It can stay firm for weeks as it is reabsorbed. See a doctor if it grows, becomes red and hot, or has not shrunk after about 4 weeks.

Should a lipoma on my leg be removed?

Not necessarily. Small, soft, painless lipomas can be left alone. Removal is considered if one is painful, growing quickly, larger than 5 cm or uncertain on a scan, in which case imaging comes before surgery.