**6. Plica excision**

### **6.1 History and physical examination**

Plicae are remnants of synovial membranes, which divide the embryologic knee into compartments. Plicae are traditionally described based on their anatomic location as suprapatellar, infrapatellar, and medial patellar or medial shelf. Lateral plicae have also been described, but are uncommon.

The suprapatellar plica is seen as a complete or partial synovial membrane that lies proximal to the proximal pole of the patella in the suprapatellar pouch. Arthroscopic studies have described an incidence of some form of suprapatellar plica as high as 87%. 36 The infrapatellar plica originates in the intercondylar notch and inserts into the synovium around the infrapatellar fat pad. Posteriorly, it may be separate from the ACL or attached to it. It is commonly seen during arthroscopy, with an incidence up to 86%. 36 The medial patellar plica originates on the medial wall of the knee, passes obliquely and inferiorly, sometimes crossing the suprapatellar plica, and inserts into the synovium surrounding the infrapatellar fat pad. The true incidence of the medial plica is unknown.

The presence of a plicae does not necessarily indicate a pathologic condition. However, plicae may become symptomatic if thickened, hypertrophic, inflamed and/or fibrotic. 37 The medial plica is most commonly pathologic, resulting in snapping or abrasion against the femoral condyle.

Pathologic plicae are notoriously difficult to diagnose because of their relative rarity, and shared symptoms with other more common knee pathology. There is often a history of trauma or repetitive stress, which may convert a non-pathologic plica into a symptomatic one. Patients mostly complain of pain in the location of the plica, which is usually exacerbated by activity, specifically kneeling or crouching. The incidence of swelling, clicking, or catching varies widely. Provocative meniscal tests and test for patellofemoral pathology are often positive, which further complicates the diagnosis. A thickened medial plica is occasionally palpable medially, just proximal to the joint line, which may be tender and felt to catch with flexion and extension. MRI can often demonstrate the presence of a plica, but not whether it is pathologic.
