What causes knee locking?

True locking means the knee cannot fully bend or straighten, often because something is obstructing its movement. A meniscus tear can create catching after a twist. A cartilage injury or osteochondritis dissecans may leave an unstable piece that interferes with motion. Plica syndrome can irritate tissue near the kneecap and cause snapping or a catching sensation. Pain and swelling can also make movement feel blocked without a physical obstruction.

Do not force the knee through a stuck position or repeatedly test it with deep squats. Rest from twisting and impact, use comfortable gentle movement, and record when the episode happens. An examination can distinguish restricted motion from pain-related stiffness and may guide decisions about imaging or rehabilitation.

Arrange prompt assessment if the knee remains locked, repeatedly catches, swells after an injury, or prevents normal walking. Seek urgent care after a major injury, visible deformity, severe swelling, or inability to bear weight. A brief painless click is different from a knee that cannot straighten.

Is my motion physically blocked or limited by pain? Could the meniscus or cartilage be involved? What activity should I avoid while it is catching? Would physiotherapy be appropriate after the cause is clearer?