Knees which snap and pop will bring many patients in the door. Some patients have painful popping or grinding of their knee. Most simply have grinding, popping or snapping without pain. Some of you might recall an injury, but most of you will not remember being injured. In many cases your knee simply started popping or snapping one day. Not all cases of knee popping require treatment, but some do.
The vast majority of people with grinding or popping in their knee do not have pain, and do not need to worry. There are some interesting scientific studies which show that people whose knees grind, and click become very fearful. They worry that the clicking or grinding in their knee means that they are wearing away their cartilage. They worry that this means that they will develop osteoarthritis of the knee. For the vast majority of you, your knees are grinding or clicking (what we refer to as knee crepitus) because of normal structures moving around in the joint. That means that this will not cause osteoarthritis. There are MRI studies which showed that the sound when we crack our knuckles is caused by gas bubble expansion. That is not dangerous. There are studies which show that normal joint fluid moving within our knees can cause clicking. Again, that is normal.
Now, there are those of you who might have painful clicking, snapping or popping in your knee. Let’s explore some of the more common reasons for painful knee clicking, popping and snapping.
What Makes Our Knees Snap and Pop?
Our knee joint is composed of three bones — the end of the femur or thigh bone; the top of the tibia or shinbone, and the patella, or kneecap. The knee is supported or held together by a number of ligaments. The knee moves because of a number of large strong muscles and tendons. Our two meniscus discs provide shock absorption.
All of these structures can be damaged by activity, trauma, injury or simple degeneration. Many injuries to the knee structures mentioned above can cause snapping and popping of your knee.
Most common cause of knee popping, snapping or grinding:
- Chondromalacia: Is a condition where the cartilage under your kneecap is starting to degenerate. As the cartilage degenerates the surface can become rough. That rough surface will rub against the femur and cause snapping, clicking or popping. Click here to read more about chondromalacia.
- Meniscus tears: The two menisci are stuck between the end of the femur and top of the tibia. They are C-shaped discs that help support the knee and protect the cartilage surfaces. Because a meniscus is between the two bones, a torn meniscus with a loose flap can easily cause the knee to snap, pop or crack with turning, twisting and squatting. Click here to learn more about meniscus tears?
- Cartilage Defects:
The bones of our knee are covered by a thick smooth layer of “articular cartilage”. Injuries and certain diseases like Osteochondritis Dessicans (OCD) can cause defects or holes to occur in the cartilage layer. If you have a cartilage defect then the surfaces of your knee are no longer smooth, and your knee is likely to pop, snap or grind.This is an uncommon cause of painful snapping in the knee. Procedures such as MACI are making it easier to heal cartilage defects or injuries. Click here to learn more about cartilage defects.
- Kneecap Dislocations: Dislocations of the kneecap or patella are far more common than we used to believe. If you were participating in a sport, twisted and felt a pop then there is a chance that your kneecap dislocated. The patella or kneecap sits in a groove on the front of your femur. It should sit perfectly centered within that groove. Sometimes the patella tilts to one side, or sometimes it slides out of the groove completely. We cover patella dislocations and malalignment as a cause of knee popping in this post. This is a very complex issue that requires an evaluation by an Orthopedist who specializes in disorders of the patella and mal-tracking or instability disorders.
- Plica syndrome: A plica is a small fold of tissue inside your knee. Many people have a plica, but very few have snapping or pain. Over time and with chronic repetitive stress a plica may become thicker and more inflamed. If a plica becomes thick and inflamed it may cause painful snapping on the inner side of your knee. Read this post on plica syndromes for more.
- Osteoarthritis: By definition, osteoarthritis implies a degeneration or “thinning” of the cartilage you have on the ends of your bones. Normal cartilage is incredibly smooth. As arthritis progresses the cartilage will undergo changes that cause significant roughness to the surfaces of the knee. Sometimes the cartilage can even peel off the bone leaving a defect or crater in the cartilage. As the ends of your bones move on one another, any irregularity in the surface can cause snapping and popping within the knee. Many find that wearing a compression sleeve significantly diminishes the pain of arthritis.
If simple remedies such as a compression knee sleeve, stretching, and time for recovery do not result in relief, consider seeing your doctor if you are concerned.
There are many less common causes of knee snapping and popping. The issues mentioned above usually cause painful snapping and popping within the knee. If you have painful popping, snapping and swelling you should see your doctor.
Many of you will have painless knee popping and snapping. Sometimes our knee pops or snaps for no known reason. In many situations it is simply “normal” and no treatment is necessary.
Orthopedic Surgery and Sports Medicine
Dr. Howard Luks, MD – Hawthorne, NY
Fax: (914) 789-2743