Hearing your knee clicking or popping can be unsettling, especially when it happens during everyday activities. These noises, medically known as crepitus, are very common. You might notice them when you stand up from a chair, climb the stairs, or bend your knee during exercise. While the sound can feel alarming, in many cases, knee noises are not harmful if they are not accompanied by pain, swelling, or mechanical symptoms.
Dr Jonathan Negus, a specialist orthopaedic knee surgeon in Sydney, regularly assesses people who are worried about new or changing joint sounds. The key factor is whether the noise is simply a sensation or whether it comes with symptoms that could indicate an underlying issue.
Understanding Knee Noises That Are Usually Harmless
It can be reassuring to know that many knee sounds are normal and occur in joints that are otherwise healthy. These noises may happen more often during periods of fatigue, after long periods of sitting, or when you begin a movement that places the knee under load.
In most cases, these sounds are not linked with injury or long-term damage, especially if they are not accompanied by pain, swelling, or instability. The following explanations describe the most common non-worrisome causes of knee popping.
Joint Fluid Cavitation and the Distinct Pop
Inside your knee is synovial fluid that helps lubricate the joint and reduce friction. When you bend or straighten your knee, pressure within this fluid can change suddenly. This rapid shift may cause microscopic gas bubbles to form and then collapse, creating a solitary popping sound.
This is known as cavitation.
Cavitation is typically painless and often occurs after the knee has been still for a period of time, such as rising from a chair or bed. Research suggests this process is typically considered benign and is not thought to cause cartilage wear or structural damage.
Tendons or Ligaments Snapping Over Bone
Around the knee are several tendons that guide movement and stabilise the joint. If one of these tendons becomes tight or if muscle balance changes, the tendon may briefly catch on a bony point before sliding back into place. This creates a soft click or snapping sensation.
This type of noise can occur with iliotibial band tightness, quadriceps or hamstring tension, or changes in strength due to altered training loads. It is common in active individuals and is usually more noticeable during repetitive bending or straightening.
Although the sensation can feel strange, it is rarely harmful and may improve with physiotherapy that focuses on stretching, strengthening, and activity modification.
Benign Cartilage Surface Irregularities
Even in healthy knees, cartilage is not perfectly smooth. Minor variations on the cartilage surface can lead to a low-grade crunching or grating sensation. This is one of the potential causes of a low-grade grinding in the knee when bending, such as during squatting or kneeling.
If the sensation is mild and not associated with discomfort, it often reflects normal cartilage texture rather than significant degeneration. Some people become aware of these noises during exercise or when first starting a new activity. In most cases, the sensation settles as the joint warms up.
Knee Noises That May Need Specialist Assessment
While harmless crepitus is common, knee noises become more significant when symptoms suggest that the joint structures are irritated, inflamed, or mechanically obstructed. The following descriptions outline situations where speaking with your GP or a knee specialist in Sydney may be appropriate. The goal is not to create concern but to help you recognise when symptoms could indicate a deeper issue.
Symptoms That May Indicate a Problem
Noises alone are not usually a warning sign. What matters most is when they occur together with one or more symptoms, such as:
Pain With Clicking or Popping
Pain that happens at the same time as the noise may suggest irritation of soft tissue or cartilage within the joint. This pain may be sharp, catching, or felt deep inside the knee. Persistent pain or increasing discomfort warrants clinical assessment.
Mechanical Locking
Mechanical locking is more than stiffness. It refers to the knee becoming stuck in a position and being unable to fully straighten or bend. If you experience knee locking symptoms, this may indicate that something inside the joint, such as a torn piece of cartilage, is affecting smooth movement and may warrant clinical review.
Instability or Giving Way
If your knee feels unreliable and lacks knee stability (gives way), especially after a loud pop during physical activity, this may be a sign of ligament injury.
ACL injuries, for example, often present with a distinct pop and immediate instability.
Persistent Swelling
Swelling that returns after activity or persists for days can reflect inflammation or internal joint irritation. Swelling combined with clicking or popping may warrant a more detailed clinical assessment.
Conditions Linked With Symptomatic Crepitus
When noises occur with symptoms, they may be associated with structural changes or injuries within the knee.
Meniscal Tears
A torn meniscus can create catching or popping sensations. Depending on the shape and position of the tear, you may notice locking, reduced range of motion, or swelling. Some tears can be managed with non-surgical treatment, while others may require knee arthroscopy if mechanical symptoms persist.
Articular Cartilage Wear or Osteoarthritis
As cartilage thins or becomes uneven, the knee may produce grinding or grating sounds, particularly during weight-bearing. This process can develop gradually over time and may contribute to stiffness or aching. Management options vary depending on the severity and may include physiotherapy, lifestyle adjustments, injection therapies, or, in advanced cases of knee arthritis, partial knee replacement or total knee replacement.
Patellofemoral Maltracking
When the kneecap does not glide smoothly in its groove, it may create clicking or grinding sensations under the patella, which may be related to Patellofemoral Pain Syndrome. This often occurs during stair climbing, squatting, or prolonged sitting. Physiotherapy is a key part of early management, with surgical options reserved for specific cases.
Ligament Injury
A loud pop at the time of injury can occur with ACL or PCL tears. These injuries may cause swelling, instability, or difficulty bearing weight. Treatment varies depending on your activity level, age, and functional goals, and may include rehabilitation or ligament reconstruction.
How a Specialist Knee Surgeon Approaches Diagnosis
A thorough clinical assessment can help you understand why the noise is occurring and what steps might support your knee health.
History and Symptom Review
You will be asked about when the sound began, which movements trigger it, and whether it is associated with pain, swelling, locking, or instability.
Physical Examination
The examination may include special tests that assess the meniscus, ligaments, or patellar tracking. Strength and flexibility are also reviewed.
Imaging
Depending on your symptoms, imaging may include:
- Weight-Bearing X-rays: These assess bone alignment and joint space changes.
- MRI: MRI scans show the condition of the menisci, cartilage, cruciate ligaments, and other soft tissues.
If surgical treatment is recommended, options may include knee arthroscopy for suitable mechanical problems, ligament reconstruction, or joint replacement when arthritis is advanced. When knee replacement is considered, robotic knee replacement surgery may be used to help support surgical planning and implant positioning.
Dr Negus uses the Mako Total Knee SmartRobotics system, which relies on CT-based imaging, and the VELYS Robotic-Assisted Solution, which creates an intra-operative model without the need for a CT scan. There is no additional cost for robotic surgery at participating hospitals in Dr Negus’s practice.
As a general guide, surgical fees for knee procedures may range from $3,000 to $8,000, depending on the procedure, hospital, insurer, and your individual cover. Fee structures vary between hospitals and states, so it is important to confirm details directly.
Taking the Next Step If You Are Concerned
If your knee is clicking or popping without pain or swelling, it may be a normal physiological sound. If the noise is persistent and accompanied by discomfort, locking, or instability, a clinical assessment may help identify the cause and guide your next steps. Dr Jonathan Negus provides evidence-based care with treatment plans tailored to your condition and goals.
If you would like to learn more about your knee symptoms or discuss your treatment options, you can arrange a consultation with Dr Jonathan Negus at our Sydney clinic.
Disclaimer: The information on this page is for general education only and is not a substitute for medical advice. Outcomes and recovery can vary between individuals. Always seek personalised assessment and guidance from your GP or a qualified knee specialist before deciding on any investigation, surgery, or treatment.
Frequently Asked Questions (FAQs) About Knee Clicking and Popping
1. Can I continue exercising if my knee clicks but doesn’t hurt?
In many cases, it is reasonable to continue exercising if the clicking is painless. If the sound is benign joint fluid cavitation or a snapping tendon, continued, gentle activity is usually safe. Focus on maintaining muscle strength and flexibility. However, if the noise increases or you start to feel discomfort, it is advisable to temporarily reduce the intensity of the activity and seek an assessment.
2. Is there a specific type of exercise that can help reduce non-painful knee clicking?
Exercises that strengthen the muscles around the knee, particularly the quadriceps, hamstrings, and hip stabilisers, can often help. Improving muscle balance and control may help the kneecap track more smoothly and reduce benign tendon snapping. A physiotherapist can provide a tailored program focusing on strength, flexibility, and proper form.
3. Does the noise’s volume (loud vs. soft) indicate whether it is serious?
The volume of the noise is not a reliable indicator of the seriousness of the issue. A loud, distinct ‘pop’ when standing up is often the harmless cavitation of joint fluid. In contrast, a soft, persistent ‘grinding’ or ‘creaking’ that occurs with pain during movement might be more concerning, as it could suggest surface irritation. The key factor remains the presence of accompanying symptoms like pain, swelling, or locking.
4. What is the difference between “locking” and “catching” in the knee?
Mechanical Locking means the knee gets truly stuck and cannot fully straighten or bend, often requiring a specific manoeuvre to unlock it. This may signal a physical obstruction, like a meniscal tear. Catching is a fleeting sensation of hesitation or momentary sticking during movement, which is often less concerning and can relate to minor soft tissue irritation or subtle patellar tracking issues.
5. If I have painful crepitus, what non-surgical treatments are typically tried first?
The initial management for painful crepitus often focuses on conservative, non-surgical approaches. This may include tailored physiotherapy to improve strength and biomechanics, modifying activities to reduce stress on the joint, and anti-inflammatory strategies. In some cases, injection therapy might be considered to help manage pain or inflammation before surgical options are explored.
6. Can supplements, such as glucosamine or chondroitin, help with knee noises or cartilage wear?
The evidence supporting the use of supplements like glucosamine and chondroitin for treating cartilage wear or reducing knee noise is often mixed. Some patients report feeling a benefit, but the supplements are not a guaranteed treatment for structural changes. If you are considering supplements, it is best to discuss this with your GP or specialist to ensure they are appropriate for your specific health needs.
7. How quickly should I seek an assessment if my knee makes a very loud pop followed by immediate instability?
If you experience your knee giving way after a loud pop during a physical activity (like playing sports), and your knee immediately swells and becomes painful, it is advisable to arrange a timely medical assessment, ideally within 24 to 48 hours. This combination of symptoms can be suggestive of a significant ligament injury, such as an ACL tear, and a specialist like Dr Jonathan Negus can assess your knee and discuss an appropriate management plan.
