Hearing a loud pop or crack sound in your knee when you perform a lunge can be disconcerting. You might feel as though you're damaging your knee joint.
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However, if you don't feel any pain along with the sound, rest assured that it's perfectly normal and won't hurt anything. On the other hand, if that noise is accompanied by pain or discomfort, it's time to stop lunging and visit your doctor.
Read more: The Benefits of Lunges
Tendons That Snap
There might be several reasons why your knee may crack or pop while doing a lunge. One of the most common is movement of your tendon over a bony prominence in your knee joint.
As your joint moves through it's range of motion, the tendon may become tight and need to adjust its gliding path. That snap back into place is the tendon sliding over the bone to return to the proper path.
This shouldn't hurt, though, and it's normal and harmless. If you have previously injured your knee joint, the cracking may also occur when the tendon passes over built-up scar tissue.
Fluid That Crackles
Another potential cause of knee cracking during lunges is gases escaping from the fluid inside of the joint. Joints are filled with synovial fluid which helps to cushion them.
As the joint moves, small bubbles of nitrogen may be pushed into or out of the synovial fluid, causing a popping sound. Like the movement of the tendon, this is normal and not harmful.
Read more: Should I Do Lunges Daily?
Snap, Crackle, Pop
While most noises in the knee during lunges are harmless, many people are concerned with issues that may develop over time. Pain-free cracking does not lead to osteoarthritis or any other joint damage.
While the sound may be unpleasant, it is not cause for alarm or treatment. There are no medications, supplements or dietary modifications that will reduce the cracking or popping sound.
To avoid the snapping or cracking sound, you may opt to not drop as low on your lunge. Stopping before the crack may not be as effective as a full lunge but it may ease your mind and make you feel more comfortable. As you become stronger and more confident, start to move through a lower range of motion.
Read more: Ew, Why Are My Joints Cracking and Popping?
Time to Visit Your Doctor
While cracking and popping in the knee is considered harmless, there are certain symptoms that may indicate a more serious issue.
If cracking is accompanied by pain or discomfort, you should consult with your physician. If you notice any swelling, have a reduced range of motion in the joint, or the joint gets locked or stuck when it cracks or pops, you should be evaluated by a doctor.
Any of these symptoms may be indicative of damage to the cartilage or tendons and may require treatment. Ignoring these symptoms may lead to chronic problems down the line. As with all exercise programs, consult with your physician and a qualified exercise professional before you begin.