Pellegrini-Stieda lesions are ossified post-traumatic lesions adjacent to the margin of the medial femoral condyle.

Clinical presentation

Most patients are asymptomatic, while a small proportion will have medial knee pain (Pellegrini-Stieda syndrome) ⁷.

Pathology

Pelligrini Stieda lesions likely represent a range of traumatic lesions, with possible origins including:

• medial collateral ligament (MCL)

  • avulsion fracture of the superficial MCL attachment at the medial femoral condyle (Stieda fracture) ^5,7

  • deep MCL ⁶

• adductor magnus muscle ischiocondylar insertion ^2,5

• medial femoral condyle periosteal stripping ²

• medial patellofemoral ligament insertion ⁶

Calcification/ossification usually begins to form 3-4 weeks after the initial injury ⁵.

Associations

• posterior cruciate ligament injury ²

Radiographic features

Plain radiograph

Calcification/ossicles or enthesophytes adjacent to or above the medial femoral condyle, which is often linear or curvilinear in shape and parallels the femoral cortex ⁵.

MRI

Pellegrini-Stieda lesion as an ossicle or enthesophyte showing a bone marrow signal at or above the medial femoral condyle. The medial collateral ligament is usually thickened.

Treatment and prognosis

Mild and moderate cases (i.e. Pellegrini-Stieda syndrome) are often conservatively managed ⁶ with steroid injections and range-of-motion exercises. Surgical excision of calcifications and medial collateral ligament repair is considered mainly for refractory cases ^3,6.

History and etymology

This lesion was first described by German radioloist, Alban Köhler (1847–1947) in 1903 ⁷. However, it is named after Italian surgeon, Augusto Pellegrini (1877-1958), who stated the calcifications were at the origin of the MCL in 1905, and German surgeon, Alfred Stieda (1869-1945), who reported a case series in 1908 ⁷.

Differential diagnosis

• tendinous calcification in reactive arthritis: often exhibits other degenerative changes

• calcific tendinitis