The sound of your knee popping may be alarming, but in most cases, it isn’t anything serious. You may experience knee pops when walking, bending the joint, or extending the knee to sit or do an exercise. Sounds coming from the knee joint are not unusual, and can be caused by several things. If the popping causes pain or limits mobility, see an orthopedic knee specialist.

The Anatomy of the Knee Joint

To better understand what’s happening inside the joint when it pops and clicks, get to know the anatomy of the knee:

 A soccer player sits on the ground holding his knee in pain.

  • Bones. The knee joint exists at the meeting point between the femur in the upper leg, and the tibia (often called the shinbone) in the lower leg. The patella or kneecap is a shield-like bone that sits in front of the intersection of the femur and tibia.
  • Cartilage. Cartilage is elastic connective tissue. Cartilage coats the ends of the tibia and femur to lubricate movement between the bones. There are also two pieces of cartilage, an inner and outer meniscus, on either side of the patella for shock absorption.
  • Tendons. Tendons connect bones of the joint to the leg muscles.
  • Ligaments. Ligaments connect bones to other bones, and provide stability in the knee joint. The medial and lateral collateral ligaments stabilize the inside and outside of the knee. The anterior cruciate ligament (ACL) keeps the joint from moving too far forward, while the posterior cruciate ligament (PCL) prevents too much backward movement.
  • Synovium. A joint capsule surrounds the knee structure. The inner layer is called the synovium, and it releases synovial fluid to lubricate the joint.

Why Is My Knee Popping?

The knee joint includes several different components. Their movements with respect to each other can lead to a host of different sounds. Crepitus is the medical term for this, and there are many potential causes. This is true whether you hear knee popping when walking, or while engaging in more vigorous activities.

Gas Bubbles

Bubbles of gas often form in the synovial fluid around the joint. When you move or bend the joint, these bubbles burst, causing popping sounds. This is completely normal, and not a concern.

Unique Joint Physiology

Everyone is different, and some people have structural abnormalities in their knees that make them noisier. For instance, if you have a small protrusion on a bone, one of the ligaments may stretch over it and then snap back into place, creating a sound.

Meniscus Tear

One of the most common knee injuries to cause popping is a tear in the meniscus ligament. Active people are susceptible to these small tears that can be noisy as the joint bends and extends.

Patellofemoral Pain Syndrome

PFS, or runner’s knee, is damage and pain behind the kneecap. It may cause popping or cracking sounds in the joint. It can occur if you run a lot of miles, especially if you increase your mileage too quickly. PFS can also result from other activities, like squatting and jumping.


Osteoarthritis is the type of arthritis usually caused by wear and tear. It is more likely to begin around the age of 50 or older, but people who participate in sports for many years can develop it earlier.

Osteoarthritis is the breakdown of cushioning cartilage in the joint. As the cartilage deteriorates, bone rubs on bone, causing pain, inflammation, and clicking, cracking, or popping sounds.

Knee Popping and Pain – When to See a Doctor

Most of the causes of knee popping are not serious and don’t require treatment. The main criteria for determining if you need to see a doctor are pain and mobility. If you experience pain with the sound, or have limited mobility, get it checked out.

A sudden knee popping sound during activity, accompanied by pain, could be a ligament tear. The most common ligament injury in the knee is to the ACL, usually during a sudden twisting or turning motion. You might tear your ACL playing basketball or soccer, getting tackled in a football game, or turning wrong or stopping suddenly during a run.

A pop with immediate pain, swelling, or difficulty moving or putting weight on the joint warrants emergency or urgent care. You can wait but should still see a doctor if a popping sound occurs with mild or occasional pain or limits your mobility only minimally. It’s possible to manage minor injuries at home, but if the issue persists, you need professional care.

The good news about those annoying clicks and pops is that they are likely not serious. If you need more information or have troubling additional symptoms, don’t hesitate to reach out. Request an appointment, self-schedule an appointment, or call 984.279.3642 to get in touch with the knee specialists at EmergeOrthoTriangle Region.

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