Why Do My Knees Crack?

Cracking knees are actually a pretty common phenomenon. You may also hear this referred to as joint noise or crepitus, which is the medical term for crackling and grinding sounds and grating sensations in the joints. This sound or sensation is only considered serious if it is accompanied by a loss of function and/or by pain.

Crepitus is caused by a buildup of carbon dioxide in the synovial fluid of the knee joint. This fluid is a very thick liquid that can be found between the components of all joints. It provides cushioning and reduces friction between bone ends. When the joint moves, carbon dioxide is released causing a cracking sound, just like cracking your knuckles.

As long as there’s no pain associated with cracking, grinding or popping knees, there’s really no cause for alarm. Although some people believe that the presence of this sound is an indication that arthritis will eventually develop, there is actually no scientific basis for that hypothesis.

These sounds are often present throughout a person’s entire life. As long as there is no pain, they are not really a reason for concern.

What Triggers Crepitus?

Knee cracking or grinding may be caused by a number of different triggers, such as:

Tight quadriceps muscles: If your knees make noise when you are walking or running, it may be that your thigh muscles are tight. This causes tension on the kneecap and prevents it from gliding smoothly as you move. This will cause a cracking sound. Add stretching to your exercise routine and be sure to warm up before exercising to help loosen up tight muscles at the front of your thigh.
Large kneecaps: If you have very large kneecaps, they may just make noise as a normal matter of course. This is because they may not fit precisely into the groove in your knee joint. If the noise doesn’t hurt, don’t worry.
Worn or damaged cartilage or meniscus: Damaged or worn down soft tissues (i.e. meniscus or cartilage) can result in rough spots that cause noisy knees (often most noticed when squatting). This is quite common as we grow older. While it can lead to pain as time goes by, this is not necessarily a given.

If pain is present, it may mean that bits of cartilage are floating around in the knee joint. It may also mean that the meniscus, which is the cushion or shock absorber for your knee, may have become torn. In either case, you should see your doctor for treatment.

Floating cartilage and meniscus tears can often be treated very effectively through very minimally invasive surgery.
Misaligned joint surfaces: If the surfaces of the joint which form the knees become displaced, it can cause a vacuum. This leads to joint compression, which causes more synovial fluid flow to the joint. When this happens, the gas bubbles contained in the gas tend to collapse and this can cause a cracking sound.

Noisy Knees Q&A

What if the cracking is very loud?

Even if your knees are quite noisy, you needn’t worry unless there is pain associated with the sound.

What if the cracking starts after an injury?

If you injure your knee, you should see your doctor, with or without cracking. Knees are tricky things and may not heal properly after an injury without medical treatment.

While you are waiting to see your doctor, practice RICE. This stands for

Rest
Ice
Compression
Elevation

The sooner you can put these protocols in place, the sooner you will feel relief from pain. RICE helps promote rapid healing and recovery for all sorts of joint, muscle, tendon and ligament injuries.

If knee noise is triggered by specific activities, should I stop doing those activities?

Again, if the popping doesn’t hurt, don’t worry about it. If there is a change in comfort level, see your doctor.

What if my knee is swollen or hot?

Any change in the size of your knee joints, any swelling or any sign of fever or infection should be seen to by a doctor.

If my knees crack, do I have arthritis?

Cracking knees may mean exactly the opposite. Motion usually causes lubrication with synovial fluid, which leads to cracking. If you have arthritis, you may lose mobility in your knees, have reduced lubrication and no cracking.

How can I stop my knees from cracking?

Talk with a physical therapist to determine exactly what movements are causing noisy knees. Follow your PTs advice, which may include adding to or modifying your current exercise regimen to strengthen your knees. If your knees are misaligned, you may be advised to tape them or wear a knee brace during exercise.

Be Smart & Fit To Protect And Strengthen Your Knees

Maintaining your ideal body weight is an excellent way to keep your knees in good shape. Being just a couple of pounds overweight can cause strain on your knees. This is because each pound of body weight represents a four pound load for your knees.

Develop an active lifestyle that includes activities such as cycling, swimming and walking. All of these help strengthen your quadriceps muscles in the front of your thigh as you tone up, lose weight and gain health.

Toned quadriceps muscles stabilize your knee joints. Additionally, wearing the right shoes (in good condition) for your chosen activities helps keep your knees well aligned and stable.

Establish a regular and realistic exercise routine. If you are out of shape, start out very slowly and add incrementally as you become stronger. Remember to warm up before setting out and cool down when you are done exercising.

Resource:

Physical Activity Guidelines for Americans
https://health.gov/sites/default/files/2019-09/Physical_Activity_Guidelines_2nd_edition.pdf