Clicking, popping, cracking, or grinding sounds from the knee can become more noticeable after a stem cell injection. Hearing a new sound can be concerning, particularly when a patient is closely monitoring the knee after treatment.

In many cases, however, knee noise by itself does not mean that the injection damaged the joint or that something has gone wrong.

Knee sounds are common even in people without knee pain. A large systematic review found knee crepitus in approximately 36% of pain-free individuals and more frequently in people with osteoarthritis. What matters more is whether the sound occurs together with pain, increasing swelling, true locking, instability, or a loss of movement.

What Causes Clicking, Cracking, and Grinding in the Knee?

Not every knee sound has the same cause. A single pop or crack may come from pressure changes within the joint fluid. Other sounds may be produced as tendons or other soft tissues move during flexion and extension.

Crepitus is slightly different. It usually describes a repeated crackling, crunching, or grinding sensation during movement. It is commonly noticed around the kneecap when bending the knee, climbing stairs, squatting, or standing up.

In people with osteoarthritis, changes in cartilage and the surfaces of the joint may contribute to crepitus. Patellofemoral changes, where the kneecap moves against the femur, are particularly associated with knee crepitus. The presence of noise therefore does not identify one specific problem on its own.

Why Might Knee Sounds Become More Noticeable After an Injection?

There are several possible reasons. Immediately after an intra-articular injection, the joint may temporarily feel fuller, tighter, or slightly swollen. This can change how the knee feels during movement and may make a patient more aware of sensations that were already present.

Activity can also change after treatment. Before an injection, pain may cause a patient to avoid deep knee flexion or unconsciously restrict movement. If pain and stiffness begin to improve, that person may gradually use a larger range of motion.

As the knee moves through a greater range, the kneecap, tendons, and other structures also travel through a greater portion of their normal movement path. Sounds that were not noticeable during limited movement may then become easier to hear or feel. This does not necessarily mean that a new structural problem has developed. It may simply mean that the knee is now moving through positions it was previously avoiding.

Does a Wider Range of Motion Cause More Knee Sounds?

It can make existing sounds more noticeable, but we should be careful about saying that increased range of motion actually causes the sound.

For example, someone who previously bent the knee only to 80 degrees because of pain may later comfortably reach 110 or 120 degrees. That additional movement exposes the joint to positions that were previously rarely used.

The patella travels along the femoral groove during knee movement. Soft tissues around the knee also change position as the knee bends and straightens.

A click occurring only during deeper flexion may therefore not have been noticeable before. The important distinction is that greater movement may reveal an existing mechanical sound rather than create new damage.

There is currently no good evidence showing that improved range of motion after an MSC injection causes the knee structures to become loose or unstable.

Does Knee Cracking Mean the Cartilage Is Getting Worse?

Not necessarily. Crepitus is more common in people with osteoarthritis and has been associated with structural changes visible on X-ray and MRI. However, it is also common in people who have no knee pain at all. This means knee noise cannot tell us by itself whether cartilage is improving or deteriorating.

A patient who has more cracking but less pain and better function should not automatically assume that the knee has become worse.

Likewise, a completely quiet knee is not proof that the cartilage is healthy.

Cartilage condition needs to be interpreted using the whole clinical picture, including symptoms, physical examination, function, and imaging when appropriate.

Can a Meniscus Tear Cause Clicking or Popping?

It can, but clicking does not automatically mean that the meniscus is torn.

This is a common misconception. Meniscal tears may produce symptoms such as pain, catching, or occasionally locking. However, research shows that mechanical symptoms are not very specific for meniscal tears. Clicking, catching, and similar sensations also occur in people with cartilage damage and osteoarthritis.

A 2025 review of degenerative meniscal tears also emphasized that clicking, popping, and locking can arise through several different mechanisms rather than from the torn meniscus alone. This is why a new click should not immediately be interpreted as a new meniscal injury.

What Is the Difference Between Clicking and True Knee Locking?

This distinction is important. A knee that clicks while still moving normally is very different from a knee that physically becomes stuck and cannot fully bend or straighten.

Occasional clicking, popping, or grinding can occur with normal movement and does not automatically require treatment.

True locking means that movement is mechanically restricted. The patient may feel that something inside the knee is physically preventing full extension or flexion.

A displaced meniscal fragment, loose body, or another structural problem may need to be considered in this situation.

Research also shows that patient-reported catching and locking are not always caused by a meniscal tear, so persistent mechanical restriction should be clinically evaluated rather than diagnosed from the symptom alone.

Does Knee Noise Mean the Stem Cell Treatment Failed?

No. Knee sounds are not a reliable measurement of whether stem cell therapy has succeeded or failed.

MSC treatment is generally evaluated according to outcomes such as pain, walking ability, physical function, stiffness, range of motion, and ability to perform everyday activities.

Whether the knee clicks is usually much less important. A patient could experience improved pain and mobility while still having crepitus because underlying structural changes remain present.

UC-MSC therapy should not be expected to immediately make an osteoarthritic joint mechanically silent. Similarly, the disappearance of clicking would not prove that cartilage had regenerated.

When Is Knee Noise Usually Less Concerning?

A sound is generally less concerning when it occurs without other significant symptoms.

For example, painless clicking that occurs occasionally when standing up or bending the knee may simply be observed.

A knee that makes more noise while also becoming less painful, stronger, and easier to move presents a different situation from a knee that suddenly becomes noisy together with swelling and loss of function.

This is why the sound should always be interpreted together with how the knee actually feels and functions.

When Should Knee Clicking or Popping Be Checked?

Medical review is more appropriate when a new sound occurs together with other changes. These may include:

• increasing or severe pain
• progressively increasing swelling
• significant warmth or redness
• fever or chills
• inability to comfortably bear weight
• true locking of the knee
• repeated giving way or instability
• sudden loss of range of motion
• a new traumatic injury

These symptoms do not necessarily mean there is a serious complication, but they provide more clinical information than noise alone. After an injection, increasing warmth, substantial swelling, severe pain, and fever are particularly important symptoms to report to the treating medical team.

Should You Stop Exercising Because Your Knee Makes Noise?

Not necessarily. Painless crepitus alone is generally not a reason to stop movement or rehabilitation. If a patient is gradually regaining range of motion and strength, some clicking may become more noticeable as activity increases. Avoiding all movement because of harmless noise may lead to unnecessary fear and reduced activity.

Exercise should instead be guided by symptoms and function. If a particular movement repeatedly causes significant pain, swelling, catching, or instability, it may need to be modified and assessed. The goal of rehabilitation is not necessarily to create a silent knee. It is to improve strength, movement, confidence, and function.

How Should Knee Sounds After a Stem Cell Injection Be Interpreted?

The sound itself usually provides only part of the information. Clicking, cracking, popping, and crepitus are common knee symptoms and can occur in people with or without osteoarthritis. They may become more noticeable after treatment because of temporary joint changes, greater attention to the knee, increased activity, or a wider range of movement.

The more useful questions are:

• Is the knee becoming more or less painful?
• Is swelling improving?
• Is movement becoming easier?
• Can the patient walk and perform daily activities more comfortably?
• Does the knee lock or give way?

A painless sound in a knee that is otherwise improving is very different from a new sound accompanied by worsening pain, substantial swelling, instability, or loss of movement.

Frequently Asked Questions

• Is clicking normal after a knee stem cell injection?

Knee clicking can occur and does not automatically indicate a problem. Knee sounds are common even in people without pain. The sound should be considered together with pain, swelling, movement, and function.

• Why is my knee cracking more now that I can bend it further?

If your range of motion has improved, the knee may now be moving through positions that you previously avoided because of pain or stiffness. This can make existing clicks or crepitus more noticeable. It does not necessarily mean the joint has been damaged.

• Does cracking mean my cartilage is rubbing away?

Not necessarily. Crepitus is associated with osteoarthritis in some people, but it is also common in pain-free knees. Sound alone cannot determine the condition of the cartilage.

• Can a meniscus tear cause knee clicking?

Yes, but clicking is not specific to meniscal tears. Cartilage changes, osteoarthritis, soft tissue movement, and other conditions can cause similar symptoms.

• When should I worry about knee sounds after an injection?

Contact the treating medical team if a new sound occurs with severe or increasing pain, substantial swelling, warmth, redness, fever, true locking, instability, or significant difficulty bearing weight.

Related Reading

• Why Does Pain Sometimes Get Worse After a Stem Cell Injection?
• Does Swelling After a Knee Stem Cell Injection Mean Something Is Wrong?
• Can You Exercise After a Stem Cell Injection?
• Why Rehabilitation Matters After Stem Cell Therapy

Medically reviewed by Dr.Apisit Rattanatanasarn, M.D. Orthopedic Surgeon

About EDNA Wellness

EDNA Wellness is a surgeon-led regenerative medicine center in Bangkok, specializing in orthopedic and neurological conditions using Umbilical Cord Derived Mesenchymal Stem Cells (UC-MSCs).

All cases are reviewed by orthopedic surgeons and neurosurgeons, with a focus on clinical indication, patient safety, and realistic treatment expectations. Stem cell therapy is recommended selectively, and alternative treatments are considered when more appropriate.

For more information or to book a consultation:

LINE: @ednawellness
WhatsApp: +66 (0) 64 505 5599
Website: www.ednawellness.com

References

• Culvenor AG, et al. Noisy knees: knee crepitus prevalence and association with structural pathology: a systematic review and meta-analysis. British Journal of Sports Medicine. 2025. https://pubmed.ncbi.nlm.nih.gov/39375004/
• Schiphof D, van Middelkoop M, de Klerk BM, et al. Crepitus is a first indication of patellofemoral osteoarthritis (and not of tibiofemoral osteoarthritis). Osteoarthritis and Cartilage. 2014. https://pubmed.ncbi.nlm.nih.gov/24583066/
• McHugh CG, Matzkin EG, Katz JN. Mechanical symptoms and meniscal tear: a reappraisal. Osteoarthritis and Cartilage. 2022. https://pubmed.ncbi.nlm.nih.gov/34600120/
• Farina EM, Lowenstein NA, Chang Y, et al. Meniscal and Mechanical Symptoms Are Associated with Cartilage Damage, Not Meniscal Pathology. Journal of Bone and Joint Surgery. 2021. https://pubmed.ncbi.nlm.nih.gov/33448713/
• Potential sources of pain in symptomatic degenerative meniscal tear: A narrative review. Osteoarthritis and Cartilage. 2025. https://pubmed.ncbi.nlm.nih.gov/40487806/