Read below about painful knee lump, including causes and common questions. Or get a personalized analysis of your painful knee lump from our A.I. health assistant. At Buoy, we build tools that help you know what’s wrong right now and how to get the right care.

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6 Potential Painful Knee Lump Causes

Disclaimer: The article does not replace an evaluation by a physician. Information on this page is provided as an information resource only, and is not to be used or relied on for any diagnostic or treatment purposes.

  1. 1.Skin Abscess

    A skin abscess is an infection of the deeper skin that's typically due to bacteria seen on the skin. Recently, infections are more frequently caused by Staph. Aureus (puts the "staph" in "staph infections").

    Good prognosis with treatment

    Rarity:
    Common
    Top Symptoms:
    large knee lump, painful knee lump, marble-size knee lump, pink or red knee bump, yellow or white knee bump
    Symptoms that never occur with skin abscess:
    fever
    Urgency:
    Primary care doctor
  2. 2.Pimple

    Acne, also known as pimples, occurs when hair follicles become clogged with oil & dead skin cells. Acne is extremely common and ranges from mild to severe.

    The severity of the acne dictates treatment-type and duration. With proper treatment, acne should resolve in weeks to months. In some cases, acne is a long-term condition.

    Rarity:
    Common
    Top Symptoms:
    pink or red knee bump, painful knee lump, marble-size knee lump, small knee lump
    Symptoms that always occur with pimple:
    pink or red knee bump
    Urgency:
    Self-treatment
  3. 3.Severe Skin Abscess

    A skin abscess is an infection of the deeper skin that's typically due to bacteria seen on the skin. Recently, infections are more frequently caused by Staph. Aureus (puts the "staph" in "staph infections"). If the infection begins to spread, urgent treatment is required.

    92-96% resolve with treatment within 7-10 days

    Rarity:
    Rare
    Top Symptoms:
    fatigue, fever, painful knee lump, pink or red knee bump, large knee lump
    Symptoms that always occur with severe skin abscess:
    pink or red knee bump, red bump
    Urgency:
    Hospital emergency room

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  4. 4.Boil (Furuncle)

    Boils are infections of a hair follicle that creates a small pocket of inflammation full of pus. It's typically caused by a common bacteria called S. Aureus.

    5-10 days

    Rarity:
    Uncommon
    Top Symptoms:
    pink or red knee bump, painful knee lump, marble-size knee lump, small knee lump
    Symptoms that always occur with boil (furuncle):
    pink or red knee bump
    Symptoms that never occur with boil (furuncle):
    fever
    Urgency:
    Self-treatment
  5. 5.Baker's Cyst (Popliteal Cyst)

    A Baker's cyst, also called as Popliteal cyst, is a fluid-filled mass that causes a bulge and a feeling of tightness behind the knee. The pain can get worse when the knee is fully flexed or extended.

    Recovery with nonsurgical treatment varies

    Rarity:
    Uncommon
    Top Symptoms:
    calf pain, swollen knee, knee pain that gets worse when squatting, knee instability, dull, achy knee pain
    Symptoms that always occur with baker's cyst (popliteal cyst):
    lump on the back of the knee, constant knee lump
    Urgency:
    Primary care doctor
  6. 6.Cherry Angioma

    A cherry angioma is a noncancerous (benign) skin growth made up of blood vessels.

    Indefinite

    Rarity:
    Rare
    Top Symptoms:
    small knee lump, cherry red knee bump, unchanged knee bump
    Symptoms that always occur with cherry angioma:
    small knee lump, cherry red knee bump, unchanged knee bump
    Symptoms that never occur with cherry angioma:
    painful knee lump
    Urgency:
    Wait and watch

Questions Your Doctor May Ask About Painful Knee Lump

  • Q.What color is the bump?
  • Q.Any fever today or during the last week?
  • Q.Is your bump getting bigger?
  • Q.Where is your knee pain?

If you've answered yes to one or more of these questions, try our painful knee lump symptom checker to find out more.

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Painful Knee Lump Symptom Checker Statistics

  • People who have experienced painful knee lump have also experienced:

    • 12% Knee Pain
    • 8% Knee That Clicks During Movement
    • 6% Moderate Knee Pain
  • People who have experienced painful knee lump had symptoms persist for:

    • 39% Over a Month
    • 26% Less Than a Week
    • 15% Less Than a Day
  • People who have experienced painful knee lump were most often matched with:

    • 35% Skin Abscess
    • 8% Pimple
  • Source: Aggregated and anonymized results from visits to the Buoy AI health assistant (check it out by clicking on “Take Quiz”).

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