Knee clicking or popping (commonly referred to as “crepitus”) is extremely common and not necessarily a sign of underlying damage. A 2025 systematic review (by Weidmann et al. in Osteoarthritis and Cartilage) analyzed over 42,000 knees and found crepitus in 41% of all knees, with 36% of those being in pain-free knees. This indicates that knee noise alone is usually asymptomatic and can be normal.
The causes of crepitus are varied. Biomechanical research shows that clicking may come from gas bubbles releasing within synovial fluid, tendons or ligaments gliding over bony landmarks, or changes in patellofemoral joint contact. Some studies, however, have linked persistent crepitus to structural knee changes. Research from the Osteoarthritis Initiative by Scholten-Peeters et al. in 2017 found that people reporting frequent crepitus had significantly higher odds of developing symptomatic knee osteoarthritis over time.
Similarly, MRI-based research shows that crepitus can correspond with underlying patellofemoral joint abnormalities. Culvenor et al. in 2014 reported that women with crepitus but no knee pain had significantly higher rates of MRI-detected cartilage defects, bone marrow lesions, and cysts. This does not mean crepitus guarantees damage, but in some individuals it may reflect early structural change.
After knee injury, crepitus may have different implications. A 2025 study by Filbay et al. examined young adults one year after ACL reconstruction and found those with crepitus had a 2.7-times higher prevalence of full-thickness patellofemoral cartilage defects on MRI. However, follow-ups over subsequent years showed that the crepitus did not predict worsening degeneration, showing that noise alone does not guarantee progression.
The functional impacts of crepitus is limited. In a 2018 study, Gustavson et al. found that although individuals with knee osteoarthritis and crepitus reported slightly worse self-rated function and quality of life, objective tests—walking speed, chair stands, strength showed no significant differences from those without crepitus. This suggests that crepitus may influence how a knee feels without substantially impairing performance.
So, when should someone seek help from a Physical Therapist with knee crepitus? Evidence suggests that a therapist evaluation is warranted when crepitus is persistent, painful, associated with swelling, instability, catching/locking, or follows a significant injury or surgery. These contexts are more often associated with meniscus tears, cartilage lesions, or joint degeneration. PT evaluation is also appropriate if knee noise comes with reduced function or fear of movement. That being said, painless clicking, especially in active, younger, or otherwise healthy individuals, is usually harmless. Strength training, mobility work, and optimized movement patterns often reduce these noises. When in doubt, it is best to seek medical advice for clarity and/or reassurance. Here at Polygon Physical Therapy, a Doctor of Physical Therapy can perform a thorough, one-on-one evaluation to assess biomechanics, identify muscle imbalances, and determine whether imaging is appropriate. Unlike clinics where you may only see a provider for a few minutes, our therapists take the time to conduct a systematic assessment and understand the full picture. When it comes to knee sounds, crepitus is common and often normal, and it’s best interpreted in context rather than in isolation. A detailed evaluation with a skilled therapist ensures you receive accurate guidance and a personalized plan for your needs.
