The patellofemoral joint, where the kneecap sits in a groove at the end of the thigh bone, is a common source of knee sounds. As the structures in this area move, individuals may hear clicking, clunking, or feel a grinding sensation within the joint. Here are four common causes:

Normal joint movement

Knees can make clicking or clunking sounds when changing positions, extending, or bending the leg. These noises often result from pressure changes within the synovial fluid, leading to the formation or release of small gas bubbles. Tendons and ligaments may also slide over surrounding structures during joint movement, creating sound. If the knee produces sounds without accompanying pain, swelling, or restricted movement, this is generally not a cause for concern.

Knee sounds can be due to normal mechanical changes or issues related to the kneecap and joint cartilage. *Illustration: Quynh Dung*.

Patellofemoral pain syndrome

Patellofemoral pain syndrome develops when the kneecap area and its surrounding structures become irritated. This condition is often associated with repetitive activities or movements that exert pressure on the knee joint. Individuals may experience grinding or clunking sounds when bending and extending the knee, accompanied by pain at the front of the knee. The pain often intensifies during activities such as climbing stairs, squatting, running, or prolonged sitting with bent knees.

Knee osteoarthritis

Knee osteoarthritis develops as the cartilage layer covering the ends of bones within the joint gradually deteriorates. When the joint surface loses its smoothness, the movement of internal structures can produce grinding sounds or a rubbing sensation. These osteoarthritis-related sounds rarely occur in isolation. Individuals often experience accompanying symptoms such as pain during movement, joint stiffness after periods of rest, swelling, or difficulty fully extending or bending the knee. This condition is more prevalent among older adults, those with a history of joint injury, or individuals who have subjected their knees to prolonged stress.

Loose or hypermobile knee joint

Some individuals possess knee joints that are more flexible than typical, or their ligaments may lack sufficient strength to maintain joint stability. Consequently, the kneecap or other structures around the joint may exhibit increased movement during physical activity, leading to audible sounds. Beyond internal joint noises, individuals might also experience a sensation of knee instability, a tendency for the knee to give way, or feel as though it might buckle when walking, changing direction, or engaging in other movements.

When should you seek medical attention?

Isolated knee sounds that cause no pain and do not impair mobility are generally not a cause for concern. However, medical evaluation is advisable if the knee frequently produces sounds accompanied by pain during activities like walking, running, climbing stairs, or squatting. Other warning signs include swelling, warmth, or joint stiffness. A doctor can thoroughly assess symptoms, review injury history, and evaluate range of motion to accurately determine the underlying cause.

Bao Bao (Compiled)