Knee locking or clicking

Noises and mechanical symptoms from the knee are among the most common reasons people seek an orthopaedic opinion. Knee locking or clicking describes a group of symptoms. The knee catches, jams, clunks, grinds or makes audible clicking sounds during movement. For some people these sensations are painless and harmless. For others, they are a sign that something inside the joint is not gliding smoothly. They may be accompanied by pain, swelling or a loss of confidence in the leg.

These symptoms can affect people of all ages, from young sportspeople after a twisting injury to older adults with age-related joint change. Patients often seek help because the knee feels unreliable on stairs. It may give way unexpectedly, or become stuck in one position for a few seconds before releasing. 

The knee is a large hinge joint formed by the thigh bone (femur), the shin bone (tibia) and the kneecap (patella). Smooth movement depends on healthy cartilage lining the bone surfaces. It also relies on two crescent-shaped shock absorbers called menisci, strong ligaments, and the surrounding muscles and tendons. When any of these structures is irritated, torn, worn or slightly out of alignment, movement can become less smooth. The joint may then click, clunk or catch.

True locking versus catching and clicking

Clinicians usually distinguish between different types of mechanical symptoms, because they point to different causes:

• True locking: the knee becomes physically stuck and cannot be fully straightened or bent. This often happens because a torn fragment of cartilage or a loose body is trapped between the joint surfaces.
• Pseudo-locking: the knee feels stuck because pain, swelling or muscle spasm temporarily limits movement, rather than because something is physically blocking it.
• Clicking or crepitus: repeated fine clicking, crackling or grinding sounds during bending and straightening, which may come from cartilage surfaces, soft tissue or the kneecap.
• Clunking or snapping: a single louder noise, sometimes from a tendon or band of tissue moving over a bony prominence.

Symptoms may come on suddenly after an injury, or develop gradually over months and years. Some people notice occasional episodes that settle on their own, while others describe a recurring or progressive pattern. Painless clicking is often completely harmless, while true locking can indicate a structural problem. An accurate diagnosis therefore matters. It prevents both unnecessary worry and unnecessary treatment.

How common are knee symptoms?

Knee symptoms are very common in the UK. Around one in four adults over 50 reports knee pain. Arthritis UK estimates that about 10 million people in the UK live with arthritis. As of 2026, knee replacement also remains one of the most frequently performed joint operations, with around 100,000 procedures recorded each year by the National Joint Registry. Most people with clicking knees, however, never need surgery.