Read below about knee injury, including causes, treatment options and remedies. Or get a personalized analysis of your knee injury 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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Knee Injury Symptoms

The anatomy of the knee is complicated, with multiple structures that are vulnerable to injury. Many athletes will experience a knee injury at some time or another. The knee is particularly likely to be injured in contact sports or sports that require rapid changes in speed and direction, like soccer. A knee injury can also occur via other types of trauma. Some injuries will heal on their own or respond to non-surgical treatment, while others require surgery to prevent further complications and ensure that healing occurs.

In addition to acute injuries, overuse of the knee due to athletic activity or daily wear and tear can cause accumulated damage over time.

Associated knee injury symptoms include:

  • Pain
  • Swelling
  • Bruising
  • Popping sound at the time of injury
  • Inability to bear weight
  • Clicking sound
  • Inability to fully extend the knee
  • Inability to fully flex the knee
  • Feeling that the knee is giving way

Knee Injury Causes Overview

Acute traumatic knee injury causes:

  • Sports injury: A direct blow to the knee, such as during a football tackle, can cause damage to one or more structures in the knee. The knee can also be injured by certain movements that don't involve a blow, such as a quick twisting motion.
  • Non-sports injury: Traumatic injury to the knee may occur in a car accident, such as if your knee hits the dashboard when the car comes to a sudden stop. Hitting your knee during a fall can also cause a serious injury.

Overuse knee injury causes:

  • Sports overuse injury: Certain sports, such as running, involve repetitive motions that can result in an overuse injury to the knee.
  • Non-sports overuse injury: Repeated use of the knee joint over time, such as kneeling for extended periods on a daily basis, can result in accumulated damage to the knee joint.

Knee injury causes in children and teenagers:

  • Some types of knee injuries are primarily seen in kids and adolescents. For example, chronic pain and injury can be associated with conditions that are caused by a sudden growth spurt.
  • Certain hip problems that occur in children cause referred pain to the knee and can be misdiagnosed as knee injuries.

9 Potential Knee Injury Causes

  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.Knee Bruise

    A knee contusion (bruise) is damage to the blood vessels (veins and capillaries) of the knee, which keeps blood from coming back out from the injured area. It is the second most common type of knee injury, behind a knee sprain.

    Less than 3 weeks

    Rarity:
    Common
    Top Symptoms:
    knee pain, constant knee pain, knee injury, knee pain from an injury, moderate knee pain
    Symptoms that always occur with knee bruise:
    knee injury, knee pain from an injury, constant knee pain
    Urgency:
    Self-treatment
  3. 3.Skin Infection of the Knee

    Cellulitis is an infection of the skin and tissues underneath it. It is most commonly caused by Group A strep and typically enters the body through a break in the skin.

    Dependent on severity of infection

    Rarity:
    Uncommon
    Top Symptoms:
    fever, knee pain, knee redness, knee injury, painful knee swelling
    Symptoms that always occur with skin infection of the knee:
    knee redness, area of skin redness
    Urgency:
    Primary care doctor
  4. 4.Infrapatellar Bursitis

    Bursae are small fluid-filled sacks located around the body in strategic locations to provide a cushion and help reduce friction. There is a pair of bursae below each kneecap (patella). Infrapatellar bursitis is a condition where these bursae are inflamed. It is a common cause of knee pain in people whose work involves frequent kneeling on hard surfaces.

    Condition goes away on its own in a few weeks.

    Rarity:
    Uncommon
    Top Symptoms:
    pain in one knee, spontaneous knee pain, dull, achy knee pain, knee pain that gets worse when going up stairs, knee pain that gets worse when squatting
    Urgency:
    Self-treatment

    Knee Injury Checker

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  5. 5.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
  6. 6.Knee (Mcl) Sprain

    The medical collateral ligament (MCL) links the thigh bone and the shin bone on the inner side of the knee joint. An MCL sprain is any damage done to this ligament (usually through twisting/force during sports).

    From 2 weeks (first-degree sprains) to between 6 to 8 weeks (second-degree sprains)

    Rarity:
    Uncommon
    Top Symptoms:
    pain in one knee, knee pain from an injury, knee injury, pain in the inside of the knee, sports injury
    Symptoms that always occur with knee (mcl) sprain:
    pain in one knee, knee pain from an injury
    Symptoms that never occur with knee (mcl) sprain:
    mild knee pain
    Urgency:
    Primary care doctor
  7. 7.Severe Kneecap Dislocation

    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.

    Physical therapy may be needed, but people usually resolve normal activities within 1 to 3 months.

    Rarity:
    Rare
    Top Symptoms:
    constant knee pain, pain in one knee, knee pain from an injury, knee injury, swollen knee
    Symptoms that always occur with severe kneecap dislocation:
    knee pain from an injury, kneecap dislocation, constant knee pain
    Urgency:
    Hospital emergency room
  8. 8.Knee Sprain (Lcl)

    The LCL is the ligament on the outside of the knee, keeping it from bending away from the body. It is most commonly injured while playing sports (ouch!) when a force is placed on the knee from the inner half of the knee.

    Days to 6-12 months, depending on severity

    Rarity:
    Rare
    Top Symptoms:
    pain in one knee, knee pain from an injury, knee injury, pain in the outside of the knee, sports injury
    Symptoms that always occur with knee sprain (lcl):
    pain in one knee, knee pain from an injury
    Symptoms that never occur with knee sprain (lcl):
    mild knee pain
    Urgency:
    Hospital emergency room
  9. 9.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

Knee Injury Treatments and Relief

Some types of knee injury symptoms require immediate imaging and treatment.

If the knee injury is severe or if blood vessels in the knee are damaged, you may even need urgent surgical or non-surgical repair. Seek emergency treatment if:

  • You are unable to bear weight on the injured knee or can only take a few steps.
  • The injury occurred via blunt trauma, such as in a car accident.
  • Your leg below the knee feels tingly, cold, or numb.
  • You have an open injury (bone, muscle, or other structures exposed).
  • Your kneecap has moved from its normal position.

Many types of knee injury symptoms require medical evaluation, even if emergency treatment isn't necessary. You will likely undergo physical exam maneuvers and possibly imaging to diagnose the injury and determine the best course of treatment.

Make an appointment with your medical provider if:

  • You had an acute knee injury, such as during an athletic event.
  • Your knee is significantly swollen.
  • You are unable to flex and/or extend your knee as much as usual.
  • You continue to have pain despite resting the knee and using over the counter pain medication.
  • Your knee feels like it is going to give way when you walk.

Your medical provider may prescribe one or more of the following knee injury treatments, depending on the type of knee injury:

  • Physical therapy, which can help relieve pain, maintain range of motion, and strengthen the knee and surrounding structures.

  • Steroid injection to reduce inflammation and relieve pain.

  • A knee brace to stabilize the knee.

  • Referral to an orthopedic surgeon for surgical management.

Some home knee injury treatments may help:

  • Try RICE treatment: Resting and Icing the knee, as well as applying Compression (such as with an ace bandage) and Elevating the knee to prevent or reduce swelling.
  • Anti-inflammatory pain relievers: NSAIDs such as ibuprofen can help. If the pain persists for more than a week, see a medical provider.
  • Weight Loss: If you are overweight, losing weight can help with overuse injuries.

FAQs About Knee Injury

Here are some frequently asked questions about knee injury.

How do you know if you have a torn meniscus in your knee?

One or both of the cartilagenous menisci in your knee can be torn in an acute injury, such as when playing sports (usually without a direct blow to the knee). A meniscus tear can also occur via damage over a long period of time. You will notice pain when flexing and extending the knee, and may also have the sensation of “locking” where you are unable to extend the knee completely. A medical provider can diagnose a torn meniscus using physical exam maneuvers and possibly imaging.

Why do I have knee pain while bending?

Pain that primarily occurs when the knees are bent, such as when sitting for a long time or when climbing stairs, may indicate a problem with the kneecap (patella) such as patellofemoral pain syndrome or patellar tendinopathy. These conditions are commonly caused by overuse, such as in sports like running, that involve frequent bending of the knees.

What is causing my sudden knee pain?

Sudden knee pain may be caused by an acute sports injury or a traumatic event like a car accident. The knee has several structures that can be injured, including the ligaments that stabilize the joint and the cartilage that protects your leg bones. Rapidly developing knee pain could also be a sign of infection, particularly if there was a previous injury to the skin over the knee and if swelling and fever are present.

Why do my knees hurt when I walk?

Knee pain when walking can be a sign of osteoarthritis, where accumulated wear and tear damage to the joint progresses over time to manifest as cartilage and bone damage. This condition is common in people over the age of 50. Knee pain with walking can also indicate a problem with the patella (kneecap), particularly if the pain tends to occur when walking up or down stairs.

Why are my knees stiff in the morning?

Knee stiffness in the morning is typically a sign of arthritis, meaning cartilage damage in the joint. There are multiple types of arthritis, which can be divided into two categories: inflammatory and non-inflammatory. With an inflammatory arthritis, such as rheumatoid arthritis or ankylosing spondylitis, pain and stiffness are worst in the morning and eventually get better with activity. With a noninflammatory arthritis, like osteoarthritis, stiffness is worse after activity rather than in the morning.

Questions Your Doctor May Ask About Knee Injury

  • Q.Did you just suffer from a high impact injury (e.g., a fall, collision, accident or sports trauma)?
  • Q.Do you feel like your knee is unstable, weak, or giving out?
  • Q.Is the knee pain affecting one or both knees?
  • Q.Where is your knee pain?

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

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Knee Injury Symptom Checker Statistics

  • People who have experienced knee injury have also experienced:

    • 15% Knee Pain
    • 10% Swollen Knee
    • 7% Knee Bruise
  • People who have experienced knee injury were most often matched with:

    • 58% Patellofemoral Pain Syndrome
    • 9% Knee Bruise
  • Source: Aggregated and anonymized results from visits to the Buoy AI health assistant (check it out by clicking on “Take Quiz”).

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.

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