What Causes Knee Cracking & How Do You Stop it?

It is quite common for everyone to hear a cracking sound whenever there is any movement in their knees, especially after getting up from a seated position for a prolonged period of time like in an airplane, going up and down stairs, walking for long distance. All these things cause the knee joint to become stiff and tight. When you hear the knee crack it gives a feeling of relaxation and pleasure and makes the knee a bit more flexible.

There are two questions that come to mind when the knees crack. The first question is why does this happen and the second question is whether it may cause some harm or injury to the knee joint. The answer to the first question has been delineated in detail below and the answer to the second question is that when there is Knee Cracking it is not the bones that are actually cracking as then it would lead to intense pain and you will not be able to move your knee. Thus, generally Knee Cracking do not cause any injury nor does it predispose you to any medical conditions, except when you already have a known diagnosis of a degenerating knee joint.

Now we go into the details of what actually produces the cracking sound with any movement of the knee. For this, we need to first understand about a fluid which is present in the body called the synovial fluid. This fluid is present between the joints in the body and acts as a lubricant or shock absorber. This synovial fluid is present in the synovial membrane which encompasses the end of our bones.

The synovial fluid prevents the bone from rubbing against each other such that there is increased friction between bones which may lead to degeneration of the bones, a condition called as arthritis.

Coming to the cracking sound, when we move a tight or stiff knee, the space between the bones gets expanded which results in a gap being created between the bones where synovial fluid rushes in to fill the gap.¹ The movement of the synovial fluid in this gap is what that produces cracking Sound.

There are certain other causes for “Knee Cracking” as well and these are:

• The cracking sound occurs when the joints are moved apart from each other creating a gap where synovial fluid forms a bubble. This bubble when it collapses or bursts causes the cracking sound.
• Another cause for Knee Cracking is believed to be over stretching of ligaments that surround the synovial membrane which produce the cracking sound.
• These causes have been hypothetically suggested as possible causes of Knee Cracking but the cause which is believed the most in medical science is the one in which the synovial fluid gushes in to fill the gap that is created when the joint is moved or stretched producing the Cracking Sound in the Knee.

As discussed above, Knee Cracking is nothing but the synovial fluid producing the sound.¹ There is no involvement of the bones or ligaments and hence there is no chance of an injury to the ankles. The only exception to this being people who have a known diagnosis of arthritis of the knee joint or an unstable knee which has a tendency to frequently dislocate. An individual with these conditions comes off a long plane ride or hikes for a significant distance can experience Knee Cracking along with pain. Apart from this, there is no data to suggest that Knee Cracking can result in any form of injury to the knee joint.

Thus, it is recommended for people who have a history of arthritis of the knees or have a weak joint which is prone to frequent dislocations to avoid sitting for prolonged periods of time, squat, walk or hike for long distances without resting for some time so as not to injure the knee.

There are a few exercises which can be done to get rid of Knee Cracking. These exercises are:

Calf Release Exercise to Get Rid of Cracking Knee: This exercise helps to relieve muscle tension with direct pressure. Simple stretching just stretches or elongates the muscle but muscle release technique actually activates the tight muscles and makes them more balanced resulting in getting rid of Knee Cracking.

To do this exercise, sit with the affected calf on top of a tennis ball. Pull the other leg on top of it and roll yourself up and down over the ball. Once you identify a tender spot then stop rolling and move the foot up and down for about half a minute. This exercise need to be done at least three times a day to get rid of Knee Cracking.

Hip Flexor Release to Get Rid of Cracking Knee: Majority of knee conditions and noises that are heard from knee including Knee Cracking are due to some abnormality of the hip. In case of Knee Cracking, this can be addressed by a Hip Flexor Release Exercise.

To do this exercise, take two tennis balls and tape them together. Now, lie on the stomach and place the taped balls beneath the stomach. Now bend the leg such that it is perpendicular to your body and swing the leg sideways from left to right such that a strain is felt on the knee. Swing the leg as much as you can tolerate.

Repeat this for the other leg. Do this at least two to three times a day in reps of three to get rid of Knee Cracking.

Inner Thigh Squats for Cracking Knee: The inner thigh is always weaker than the outer part of the quad thigh muscles. Thus to get rid of Knee Cracking, you need to strengthen the inner thigh as well. For this inner thigh squats are the best exercises that can be done.

To do this exercise, place your feet shoulder-width apart with your toes slightly tilted and not straight with the entire weight of the body on the heels. Now come down to a squatted position as if you are about to sit on a chair which is a fair distance behind you. When squatting move the knees out to the sides and go as low as you can tolerate and then come back up. Do this about 10 times and at least three times day to get rid of Knee Cracking.

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