A crackling knee (crepitus) is usually harmless gas or tissue moving in the joint. See a doctor if it hurts or swells.
What it is
Crepitus is a crackling or popping sound in the knee.
Common causes
- Gas bubbles in the joint fluid.
- Tendons or ligaments snapping over bone.
- Cartilage wear (osteoarthritis).
- Patellofemoral pain.
Is it normal
Painless crackling is usually harmless.
See a doctor
If you have pain, swelling, locking or giving way.
Care
Strengthen quads and keep a healthy weight.
Cause of knee sounds
Painless crackling, called crepitus, usually comes from gas bubbles popping in the joint fluid or tendons and ligaments snapping over bony edges. The kneecap (patella) glides in a groove on the thigh bone, and tight structures can create sounds. A review in the journal Arthritis Care and Research suggested crepitus is common, with about 1 in 3 adults over 45 reporting it in some studies.
- Patellofemoral pain syndrome (runner’s knee) combines noise with pain around or behind the kneecap and affects roughly 25 percent of active people at some time.
- Osteoarthritis creates grinding with stiffness and swelling.
- A meniscus tear causes clicking with locking or catching, and pain along the joint line.
Self-care
Strengthening the quadriceps and hips with squats, step-ups and bridges helps keep the patella in line. Low-impact exercise like cycling and swimming supports cartilage. Maintaining healthy weight reduces knee load, since each pound lost removes about 4 pounds of pressure on the knee when walking. See a doctor if noise comes with pain, swelling, locking or giving way.
Cause of knee sounds
Knee crackling is called crepitus. It is often harmless gas bubbles in joint fluid or tendons passing over bone. Painless crepitus is common. Crepitus with pain, swelling or locking can signal cartilage damage, patellofemoral pain or osteoarthritis. Osteoarthritis affects about 32.5 million US adults, according to the CDC.
Self care
Strengthen quadriceps and hips, maintain a healthy weight and use supportive shoes. See a doctor if sounds come with pain, swelling, instability or catching. Imaging such as X ray or MRI may be done.
Common causes by age
Knee crepitus is common in young people after prolonged sitting. Studies found 99 percent of adults with knee osteoarthritis have crepitus, but crepitus in healthy people is usually benign. In a 2014 study, 38 percent of young adults had knee noise during squats. Cartilage wear, patellofemoral syndrome and meniscus tears produce painful grinding.
Exercise and care
Strengthen the quadriceps, hamstrings and hip abductors, and maintain a healthy weight, since each pound lost reduces about 4 pounds of knee load. Low impact exercise such as cycling and swimming helps. See an orthopedist for painful or swollen knees.
Based on data from the Arthritis Foundation and the American Academy of Orthopaedic Surgeons
