When you’re in the middle of a workout, certain sounds are expected: the thud of weights, the rhythm of a good song, and your own heavy breathing. 

But one sound might catch you off guard—the cracking, popping, or creaking of your knees as you perform squats. 

Though startling, this noise, commonly known as crepitus, is often harmless and quite common, according to Brendan Overlid, DPT, CSCS, a physical therapist at UCHealth in Colorado.

The Phenomenon of Crepitus

Crepitus refers to any cracking, popping, or creaking sounds that occur in the joints. 

Nicole Haas, PT, DPT, founder of Boulder Physiolab in Colorado, explains that these sounds can be attributed to various factors, including the natural movement of gas within the joint fluids. 

This gas forms bubbles that can burst during joint movement, such as bending during a squat, resulting in the noises you hear.

Common Causes of Knee Noises

Gas Formation and Release

Gas bubbles naturally form in the fluid surrounding your knee joints. 

When you squat, bending the knee compresses these bubbles, causing them to pop and produce a sound. 

Ryan Chow, PT, DPT, founder of Reload Physical Therapy and Fitness in New York, likens this to the familiar cracking of knuckles. 

Once the gas is released, the joint may not produce the sound again until the gas has had a chance to reaccumulate.

Form and Movement Variations

Squats are a compound exercise involving multiple joints and muscles. 

Small variations in how a person performs a squat—such as uneven weight distribution or unnatural foot positioning—can lead to increased pressure in the knees, which may cause popping noises. 

Chow emphasizes the importance of squatting with a natural foot position, suggesting that the best stance is the one that feels most comfortable and balanced.

Potential Form Issues

Incorrect squat form, such as allowing the knees to collapse inward or not maintaining control of thigh movements, can strain the structures around the knee. 

This strain may lead to noise as the tendons and ligaments rub against each other or the bone. 

Adjusting your form to ensure proper alignment and movement can help minimize these sounds and protect your knees from potential injury.

Other Causes of Cracking Sounds

Knee cracking isn’t just limited to the common instances during exercises like squats. Beyond the gym, various other factors can cause your knees to pop, crack, or make similar noises. 

These sounds can arise from a range of sources, from natural aging to more acute conditions that might require attention. Understanding these less common triggers is crucial for maintaining knee health and identifying when to seek medical advice. 

Here, we explore some of these lesser-known reasons behind knee noises, providing insights into their causes and implications.

Age-Related Changes

As people age, the cartilage in the joints can wear down, and the synovial fluid, which lubricates the joints, may decrease. These changes can lead to more frequent and noticeable cracking or popping sounds when the knee moves.

Ligament or Tendon Movement

Sometimes, ligaments or tendons may snap over the bony structures of the knee as they move. This snapping can create a cracking sound, especially if the connective tissues are tight or if there is an abnormal alignment.

Meniscus Tears

The meniscus is a piece of cartilage that provides a cushion between your femur (thigh bone) and tibia (shin bone). A tear in the meniscus can cause a clicking or popping sound when moving the knee. This type of injury often results from trauma or a sharp, sudden movement during physical activity.

Chondromalacia Patella

This condition, also known as “runner’s knee,” involves the softening and breakdown of the cartilage on the underside of the kneecap. It can lead to a rough surface on the kneecap that may create a grinding or cracking sound during knee movements.

Joint Inflammation or Arthritis

Inflammatory conditions like arthritis can cause changes in the joints that may lead to cracking sounds. Inflammation can result in more friction or changes in the joint’s structure, leading to noises during movement.

Joint Instability

Some individuals may experience joint instability in their knees due to weak or imbalanced muscles supporting the joint. This instability can lead to abnormal movement patterns that cause the knee to crack.

Hypermobility

People with joint hypermobility syndrome may have joints that move beyond the normal range expected for that joint. This increased range of motion can sometimes lead to more frequent joint noises, including in the knees.

Deeper Issues Possibly Indicating Wear and Tear

Repetitive movements, especially high-impact activities like running and squatting, can cause wear and tear on the cartilage beneath the kneecap. 

This wear can change the smoothness of the joint movement, resulting in grinding noises. 

Haas points out that, while these sounds can be unsettling, they’re usually not a cause for concern unless accompanied by pain or other symptoms.

When to Be Concerned: Signs of Possible Knee Problems

It’s generally advised to consult a healthcare professional if knee noises are accompanied by pain, a change in the motion of the knee, swelling, or instability. 

These symptoms could indicate underlying conditions such as arthritis or meniscal injuries, which may require medical attention.

Preventive Measures and Exercises

Maintaining proper squat form is crucial for preventing knee noises and potential injuries. 

Strengthening exercises for the glutes and regular flexibility work, including foam rolling, can also help maintain knee health. 

For those experiencing frequent noises, specific stretches and strengthening exercises tailored to their needs can be beneficial.