Plica syndrome refers to conditions associated with plical pain. A plica is a fold of the tissue lining of the knee joint, which is a remnant of early development. There may be several of these folds in normal knees. Of the four common plica, which may be in any normal knee, the plica that most commonly becomes symptomatic is the one on the inner (medial) aspect of the knee and thus called the “medial plica”. Normally, a plica is small and smooth. The plica may be present for years without symptoms until it is irritated or inflamed most commonly through overuse or direct impact injury. Once it becomes irritated, it may become thickened, causing pain and further inflammation. Think of it a biting the inside lining of your mouth, which causes local pain and swelling. After that, the area is prone to “rebiting”. In much the same way, once a plica becomes irritated it is more prone to further irritation unless treated.
Although plica syndrome does not usually damage the knee (rarely, a large plica can rub on the articular cartilage and cause wear), it can be a very painful nuisance. Diagnosing plica syndrome can be tricky, but treatment is straightforward.