Pellegrini-Stieda Disease

Etiology

The etiology of Pellegrini-Stieda is thought to be an insult to the medial collateral ligament causing damage and acute inflammation that sets into motion a process of delayed ossification. This insult has been classically described as a macrotrauma, whether direct or indirect, causing valgus stress with disruption of the MCL fibers. When initially described by Kohler in 1903 the ossification was particularly associated with sports activities. However, some reports from physiatrists have suggested micro-repetitive trauma from therapeutic manipulation of a restricted knee joint or post-surgical rehabilitation to be possible etiologies of Pellegrini-Stieda Disease with new-onset medial knee pain, edema, or restricted range-of-motion in an actively rehabilitating patient.[2][3] In some cases, Pellegrini-Stieda Disease has been seen in patients without knee trauma but concomitant spinal cord injury or traumatic brain injury. This calcific development, however, becomes difficult to discern from heterotopic ossification and myositis ossificans, the incidence of which increases in these patient populations.

Epidemiology

While the exact incidence is unknown, during a seven-year retrospective study of a clinical radiology database performed by a research team affiliated with The University of Colorado and The University of Alabama at Birmingham, knee radiograph reports of 332 patients included the term "Pellegrini Stieda."[4] The condition preferentially affects males, favoring patients between the ages of twenty-five and forty-years-old.[5]

Pathophysiology

The initial insult, whether resulting from macro- or repetitive microtrauma, leads to the same result: calcific ossification of the soft tissue structures surrounding the medial femoral condyle. In the cases associated with spinal cord injury or traumatic brain injury, neurogenic precipitation of ectopic bone formation can occur by humoral, neural, and local factors including tissue hypoxia, hypercalcemia, changes in sympathetic nerve activity, prolonged immobilization and subsequent mobilization.[6] Notably, the stereotypical localization of ossification of the medial collateral ligament has been questioned as studies have suggested that magnetic resonance imaging and anatomic cadaveric verification of suspected Pellegrini-Stieda lesions have demonstrated heterogeneous distribution inferiorly.[7][4] Mendes et al. went as far to suggest an alternative classification syndrome for Pellegrini Stieda lesions of Type 1 through Type 4 based on their location. Type 1 is referred to as a beak-like appearance and describes the ossification arising from the femur and extending inferiorly in the medial collateral ligament. Type 2 defines a tear-drop pattern, localized within the medial collateral ligament without any attachment to the femur. Type 3 presents as an elongated ossification superior to the femur lying in the distal adductor magnus tendon. Type 4 is also characterized as a beak-like appearance arising from the femur. However, this ossification extends into both the medial collateral ligament and adductor magnus tendon. Therefore, the original attribution of the syndrome to the medial collateral ligament may now be outdated as many publications have suggested concomitant and even sometimes preferential involvement of the adductor magnus tendon, medial head of the gastrocnemius, or medial patellofemoral ligament.[7][4] While most patients are asymptomatic from this ossification, a small percentage experience medial knee pain (with or without restricted knee range-of-motion and knee joint swelling) defined as Pellegrini-Stieda syndrome.

History and Physical

The following represents the typical presentation of Pellegrini Stieda Disease in a clinical setting: A thirty-year-old male presents to your clinic with a history of knee-to-knee collision to the medial right knee about three weeks ago during a recreational soccer game with acute pain that resolved after rest and ice. He now presents with new onset right medial knee pain and decreased range-of-motion of the right knee joint.

Evaluation

Diagnosis is typically made on plain radiographs demonstrating Pellegrini-Stieda sign accompanied by pain or restriction of range-of-motion of the knee joint. Pellegrini-Stieda sign is typically described by a longitudinally linear opacity, characteristic of calcification in the soft tissue located medial to the medial femoral condyle. This calcification seen on imaging represents the ossification of the medial collateral ligament, which typically does not develop until approximately three weeks after the initial injury.[8] It is essential to distinguish this radiographic finding from that of a medial femoral condyle avulsion fracture - an injury in which a pulling force of a tendon or ligament fractures away a piece of the bone from its attachment site. Similarly, on magnetic resonance imaging, bone marrow signal at the medial femoral condyle is accompanied by ossified characteristics, that of an enthesophyte, of the medial collateral ligament which appears thickened. The advent of musculoskeletal ultrasonography has also proven useful in diagnosing Pellegrini-Stieda lesions and can often elicit associated edema.

Treatment / Management

Symptom duration is typically five to six months as the ossified lesion matures. The severity of the pathology will dictate the treatment plan. Mild and moderate cases are usually managed conservatively with non-steroidal anti-inflammatories, corticosteroid injections, and range-of-motion exercises. Severe refractory cases, however, are considered candidates for surgical excision of medial collateral ligament calcifications. A study by Kulowski and Riebel showed a high variance in surgical outcomes, with a high recurrence rate, while data from Pellegrini and an updated Kulowski study showed quite the opposite. Additionally, surgical studies have warned that excision of larger lesions can lead to ligamentous defects requiring surgical reconstruction.[8](B3)

Differential Diagnosis

1. Pellegrini-Stieda Disease
2. Medial collateral ligament sprain
3. Medial meniscal tear
4. Medial femoral condyle avulsion fracture
5. Myositis ossificans
6. Heterotopic ossification
7. Knee osteoarthritis
8. Semimembranosus/semitendinosus tendinitis

Prognosis

While most cases of Pellegrini-Stieda Disease have documented symptom resolution within five to six months with conservative management of non-steroidal anti-inflammatories, corticosteroid injections, and range-of-motion exercises, some severe refractory cases require surgical intervention.

Complications

Untreated Pellegrini-Stieda Disease could lead to restricted knee joint range-of-motion and contracture developing into gait abnormalities, decreased activities of daily living, and chronic pain. Some studies have suggested poor surgical outcomes with high recurrence rates or ligamentous defects with large lesion excisions requiring further surgical reconstruction.[8]