The MPP originates along the medial wall of the joint, runs obliquely downwards, and merges with the synovial membrane covering the infrapatellar fat pad. Among these plicae, a medial patellar plica (MPP) has been reported in many healthy knees, and it is asymptomatic in most cases. The presence of plicae at all these anatomical locations is an anatomical variant and not considered pathological.

They are classified according to their corresponding anatomical site, and are therefore known as suprapatellar, infrapatellar, medial, and lateral patella plicae. Synovial plicae in the knee joint are remnants of divisions between the compartments that are present in the knee during embryological development. Surgeons should be mindful that acquired plica-induced notches in the articular surface of the medial femoral condyle can present in patients with MPP syndrome. We concluded that this abnormal notch had developed gradually in the MPP without cartilage damage. However, during arthroscopic surgery, we found that the cartilage of the notch, which was located beneath the MPP, was completely intact.

We considered that the impinged hypertrophic plica between the anterior medial femoral condyle and the medial articular facet of the patella resulted in cartilage damage on the articular surface of the medial femoral condyle. Preoperative magnetic resonance imaging in a 17-year-old male patient with MPP syndrome showed a hypertrophic MPP along with an abnormal notch in the articular surface of the medial femoral condyle. In patients with MPP syndrome, cartilage damage may occur depending on the shape of the MPP and the duration of the impingement. An inflamed and thickened medial patellar plica (MPP) caused by repeated mechanical irritation from trauma or overuse leads to impingement between the anterior medial femoral condyle and the medial articular facet of the patella and produces pain or clicking, which is known as MPP syndrome.

Medial pica syndrome