Why does knee bursitis cause knee pain?

A bursa is a small fluid-filled sac that helps tissues glide and cushions pressure near the knee. Repeated kneeling, a knock, friction, or increased activity can irritate its lining. The bursa may then hold extra fluid and become sensitive. Pain can be felt over the kneecap, below the knee, or on the inner side, depending on which bursa is involved. Bending, kneeling, climbing, or direct contact may make it worse. The exact location and pattern help a clinician distinguish bursitis from joint problems, tendon irritation, or an injury.

Knee pain alone has many possible explanations. An examination is useful when symptoms persist or the cause is unclear.

Avoid kneeling and direct pressure for now, and use a cushion or knee pad when those tasks cannot be avoided. Rest from movements that clearly aggravate the area without keeping the knee completely still. Ice wrapped in cloth can be used for short periods. Gentle range-of-motion exercises may help, while a clinician or physiotherapist can tailor strengthening and activity changes. Do not puncture or drain a swollen area yourself.

Contact a clinician if swelling or pain persists, interferes with sleep or walking, or follows a significant blow. Seek prompt medical care for increasing redness, warmth, fever, drainage, or rapidly worsening pain because an infected bursa needs timely assessment. Urgent evaluation is also appropriate if you cannot bear weight or the knee appears deformed after an injury.

Which bursa seems irritated? What activities should I change, and for how long? How can I protect the knee at work or during exercise? What signs would suggest infection or a different knee problem?