Why does plica syndrome cause knee locking?

A plica is a flexible fold within the knee. Repeated bending, a sudden increase in activity, or irritation can make it thicker and less tolerant of pressure. During a bend or when the knee straightens, the fold may rub or catch near the inner part of the joint. This can feel like a brief block, a snap, or a need to move the leg before it feels free again. Knee Locking is a common presentation of Plica Syndrome, but a knee that truly cannot straighten can have other causes and should not be self-diagnosed. The timing of the episodes, swelling, injury history, and physical examination help separate these possibilities.

Pause deep squats, kneeling, jumping, and other movements that repeatedly trigger catching. Keep the knee moving gently within a comfortable range so it does not become stiff from complete rest. Cold therapy wrapped in a cloth can reduce soreness after activity. A physiotherapist may work on thigh and hip strength, movement control, and a gradual return to normal loading. Avoid forcing a locked knee through resistance or twisting it to release the sensation.

Arrange a clinical review when locking keeps returning, causes a fall, limits walking, or comes with pain or swelling. Seek urgent assessment if the knee is stuck and cannot straighten, if a major injury was followed by rapid swelling or deformity, or if the joint is hot and red with fever. These features need evaluation for problems beyond plica irritation.

Does my knee catch briefly, or is it mechanically locked? What examination findings support plica irritation? Should I change work or exercise temporarily? Which strengthening movements are safe, and when should persistent locking lead to imaging or specialist review?