Read below about pop in the knee, including causes and common questions. Or get a personalized analysis of your pop in the knee 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 Pop in the Knee 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.Patellofemoral Pain Syndrome

    The kneecap (patella) is located directly in front of the thigh bone (femur), and should normally glide freely up and down. In this condition, called patellofemoral pain syndrome, the kneecap may rub against the thigh bone instead of gliding smoothly, causing damage and pain.

    Most people get better within weeks to months of physical therapy.

    Rarity:
    Common
    Top Symptoms:
    knee pain, pain in one knee, knee pain that gets worse when going up stairs, dull, achy knee pain, knee pain that gets worse when squatting
    Symptoms that always occur with patellofemoral pain syndrome:
    knee pain
    Urgency:
    Primary care doctor
  2. 2.Repeated Kneecap Dislocation (Patellar Subluxation)

    Recurrent patellar subluxation is the continued instability of the kneecap, which causes anterior knee pain and usually occurs laterally. It occurs unpredictably with varying durations.

    Recovery timeline is dependent on treatment type.

    Rarity:
    Uncommon
    Top Symptoms:
    pain in one knee, dull, achy knee pain, pain in the front of the knee, pain in the inside of the knee, swollen knee
    Symptoms that always occur with repeated kneecap dislocation (patellar subluxation):
    kneecap dislocation
    Urgency:
    Primary care doctor
  3. 3.Dislocated Kneecap

    The kneecap connects the muscles in the front of the thigh to the shinbone (tibia). When the kneecap slips out of the groove, problems and pain often result.

    Resolves upon reduction of dislocation.

    Rarity:
    Uncommon
    Top Symptoms:
    pain in one knee, knee pain from an injury, knee injury, swollen knee, knee instability
    Symptoms that always occur with dislocated kneecap:
    kneecap sliding out to the side, knee pain from an injury
    Urgency:
    In-person visit

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  4. 4.Acl Injury

    The ACL (anterior cruciate ligament) is a super-important tendon that connects the femur (thigh bone) to the tibia (shin), keeping the tibia from flying forward every time a step is taken. Tearing happens in a lot of accidents and sports, unfortunately.

    Full recovery may take months of physical therapy.

    Rarity:
    Rare
    Top Symptoms:
    knee pain, pain in one knee, knee instability, swollen knee, knee pain from an injury
    Symptoms that always occur with acl injury:
    knee pain
    Symptoms that never occur with acl injury:
    mild knee pain
    Urgency:
    Hospital emergency room
  5. 5.Osteochondritis Dissecans

    At joints where bones meet, bones are covered with a layer of cartilage which provides shock absorbance and lubrication. Osteochondritis dissecans is a condition where a piece of cartilage with a thin layer of bone detach from the larger bone, causing pain.

    Conservative treatment should resolve the problem in 3-6 months.

    Rarity:
    Rare
    Top Symptoms:
    pain in one knee, knee stiffness, knee instability, knee pain that gets worse during a run, pop in the knee
    Urgency:
    Primary care doctor
  6. 6.Pigmented Villonodular Synovitis

    The synovium is a thin layer of tissue that surrounds joints, providing a small amount of fluid to lubricate the joint and aid in movement. In pigmented villonodular synovitis (PVNS), the synovium thickens and overgrows. This mass typically only affects one joint, is not cancerous, and does not spread to other parts of the body.

    Recovery from arthroscopic (minimally invasive surgery) is quick and can take a few weeks to a month.

    Rarity:
    Rare
    Top Symptoms:
    joint pain, pain in the outside of the hip, pain in one knee, groin pain, deep, throbbing hip pain
    Symptoms that never occur with pigmented villonodular synovitis:
    knee instability
    Urgency:
    Primary care doctor

Questions Your Doctor May Ask About Pop in the Knee

  • Q.Which of the following describes your physical fitness:
  • Q.While you are standing, take a look at your knees. Do they appear to bend towards each other, rather than follow a straight line along your legs? (Knock-kneed)
  • Q.Do you often feel your knees buckling?
  • Q.Is your knee pain:

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

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Pop in the Knee Symptom Checker Statistics

  • People who have experienced pop in the knee have also experienced:

    • 21% Knee Locking
    • 21% Knee That Clicks During Movement
    • 13% Knee Pain
  • People who have experienced pop in the knee were most often matched with:

    • 63% Patellofemoral Pain Syndrome
    • 15% Repeated Kneecap Dislocation (Patellar Subluxation)
    • 2% Dislocated Kneecap
  • 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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