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from the American Academy of Orthopaedic Surgeons

Diseases & Conditions

Treatment

Recovery

Staying Healthy

Why Do Knees Make Noise?

The knee is a complex joint made up of a variety of structures, including bone, cartilage, ligaments, tendons, and muscles. These structures work together to create a functioning joint that bears weight, bends, and straightens.  

When your knees are healthy, you likely do not think much about them; they quietly do their job, enabling you to stand, walk, work, and participate in the activities you enjoy, including sports.

normal knee anatomy

Normal knee anatomy. The knee is made up of bones, cartilage, ligaments, and tendons.

However, when you suffer damage to one or more of the structures in your knee, from an injury or due to degeneration (wear and tear over time), you may suddenly or gradually start to notice unusual noises or feelings in the knee. This can be worrisome, especially if you are also having pain or difficulty moving around.

To help you better understand what you may be hearing, feeling, and seeing, here is a breakdown of the 9 most common causes of crackling, popping, snapping, creaking, and other symptoms in the knees — including when you should see a doctor to have them checked out.

1. Arthritis

What you might hear:

  • Cracking
  • Popping
  • A creaky Velcro-like sound (this is called crepitus)

What you might feel or see:

  • Painful stiffness or tightness in the knee
  • A temperature change where your knee feels either hot or cold
  • Possibly, weakness or buckling when standing or walking

These symptoms may worsen in the morning or after sitting for a long period of time.

(Left) Healthy knee. (Right) Knee with osteoarthritis.

Common causes of knee arthritis:

  • Degenerative changes (wear and tear over time) in older patients
  • In younger patients, being overweight or experiencing trauma to the knee joint

Learn more: Arthritis of the Knee

2. Meniscus Tears

What you might hear:

  • A cracking or clicking sound at the time the injury happens and afterward while moving the knee

What you might feel or see:

  • Locking or buckling of the knee that worsens when walking and squatting; this may feel like something is catching inside the knee
  • Pain when getting out of a car or standing up from a chair or sofa
  • Painful swelling and a feeling that the knee is unstable when walking or attempting to move the knee through a full range of motion

Meniscus injuries and all other soft tissue injuries cause similar symptoms of instability, painful swelling, and a locking or catching sensation while walking or exercising. If you have these symptoms, it is important to have your knee evaluated by an orthopaedic surgeon so you can get the proper diagnosis and treatment.

MRI scans show (left) a normal meniscus and (right) a torn meniscus. The tear can be seen as a white line through the dark body of the meniscus.

Common causes of meniscus tears:

  • Sports injuries in younger patients
  • Degenerative changes (wear and tear over time) in older patients

Learn more: Meniscus Tears

3. Ligament Injuries

What you might hear:

  • A sudden popping sound when the ligament ruptures

What you might feel or see:

  • Painful swelling and buckling or catching in the knee when walking and/or pivoting
  • For some ligament injuries, a feeling of instability when moving

A complete tear of the anterior cruciate ligament (ACL).

Common causes of ligament injuries:

  • Pivoting or landing incorrectly from a jump while playing a sport (non-contact injuries)
  • A traumatic injury, like a motor vehicle accident or football tackle when the knee suffers a hard blow from the front, back, or side

Learn more: Anterior Cruciate Ligament (ACL) Injuries, Collateral Ligament Injuries, Combined Knee Ligament Injuries

4. Tendon Tears

What you might hear:

  • A popping sound when the tendon is ruptured

What you might feel or see:

  • Painful swelling and the knee buckling with an inability to straighten the knee
  • An indentation at the bottom of the kneecap, and/or the kneecap is moving into the thigh (signs that the patellar tendon is likely torn and is no longer anchored, or attached, to the shinbone)
  • An indentation (dent) at the top of the kneecap, and the kneecap is sagging or drooping (signs that the quadriceps tendon has been torn)

A complete tear of the quadriceps tendon.

Common causes of tendon tears:

  • Pivoting or landing incorrectly from a jump while playing a sport (non-contact injuries) with the foot planted and knee partially bent
  • A traumatic injury, like a laceration (cut) or a football tackle where the knee suffers a direct hard blow to the front of the knee

Learn more: Patellar Tendon Tear, Quadriceps Tendon Tear

5. Iliotibial (IT) Band Syndrome

What you might hear:

  • A popping or snapping sound from the outside (lateral side) of the knee

What you might feel or see:

  • Pain on the side of your knee that worsens with running, cycling, or performing any activity that involves repeated bending and straightening of your knee

Common causes of IT band syndrome:

  • Irritation of the iliotibial band after repeatedly rubbing against the bones of the hip or knee
  • Running (this condition is common in runners)

6. Plica Syndrome

What you might hear:

  • A popping or snapping sound from the medial side of the knee (the inside of the knee, or the side closest to the other knee)

What you might feel or see:

  • Painful catching from the inside of your kneecap
  • Tenderness on the middle side of your knee right above the joint
  • Some instability when walking
  • Possibly some swelling of the knee; you might be able to feel the swollen plica when touching your kneecap as a tender band just below the skin

Common causes of plica syndrome:

  • A traumatic injury where the knee suffers a direct hard blow to the front of the knee
  • In young athletes, running, biking, or activities that involve repetitive motion

7. Loose Bodies in the Knee Joint

What you might hear:

  • A popping or cracking sound from the inside of your knee

What you might feel or see:

  • A painful locking or catching of your knee, usually while walking; it may feel like something is blocking your knee from fully straightening out or bending

Common causes of loose bodies:

8. Patellar (Kneecap) Fractures

What you might hear:

  • Cracking at the time of the injury

What you might feel or see:

  • Painful swelling and bruising, with tenderness to touch
  • Possibly a sensation of two bones rubbing together
  • The knee looks deformed or out of place, with the injured leg appearing shorter or rotated differently (turned in a different direction) than the other leg

Illustration and X-ray show a vertical, stable fracture of the patella.

Common causes of knee fractures:

  • A high-energy injury, such as a motor vehicle collision or falling from a height onto a hard surface

Learn more: Patellar (Kneecap) Fractures

9. Prior Joint Replacement

What you might hear:

  • A clunking sound coming from the knee when you walk

What you might feel or see:

  • Possibly, nothing; it’s not uncommon after knee replacement to hear a clunking sound when you walk but not experience pain or other symptoms

Cause of joint replacement clunking:

  • The metal and plastic components (parts) of the joint replacement implant making contact when the knee moves between flexion (bending) and extension (straightening)

Learn more: Total Knee Replacement

When To See a Doctor for Knee Noises

In general, you should seek treatment as soon as possible, especially after a traumatic event or fall, or if you notice any of the following:

  • A popping noise and the feeling of the knee giving out at the time of an injury
  • Severe pain or swelling at the site of the injury
  • You cannot move the knee
  • You are limping or feel unable to bear weight on the leg

Your doctor will recommend treatment based on several factors, including the severity of your injury, and your age, general health, and activity level. Possible treatments include:

Last Reviewed

July 2023

Contributed and/or Updated by

Shreya M. Saraf, MS, BAWendell W. Cole, MDVictoria Katherine Ierulli, MS

Peer-Reviewed by

Mary K. Mulcahey, MD, FAAOSThomas Ward Throckmorton, MD, FAAOS

AAOS does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific orthopaedic advice or assistance should consult his or her orthopaedic surgeon, or locate one in your area through the AAOS Find an Orthopaedist program on this website.