chapter 8: Patellar Tilt‑Compression and the Excessive Lateral Pressure Syndrome (ELPS)
"Disease is from old and nothing about it has changed. It is we who change as we learn to recognize what was formerly imperceptible. "
—Jean Marie Charcot (1825‑1893)
Patellar tilt‑compression is characterized clinically by pain and radiologically by patellar tilt, as evidenced on the Maldague lateral radiograph, axial patellofemoral radiograph, computerized tomography (CT) scan, or magnetic resonance imaging (MRI). In the original edition of this book, Ficat and Hungerford (1) described the excessive lateral pressure syndrome (ELPS). It is important, now, to recognize that patellar tilt occurs with or without associated subluxation and may eventually cause ELPS. The concept of ELPS, however, is important because chronic lateral patellar tilt can have devastating effects on articular cartilage. Chronic alteration of pressure on the medial facet and overload on the lateral facet (caused by chronic patellar tilt) will lead to arthrosis in many patients, but associated tightness of the lateral retinaculum may result in persistent retinacular pain even before there is evidence of articular cartilage disruption.
Tilt‑compression, therefore, is a clinical‑radiographic condition of the patellofemoral joint that leads to two clinical outcomes in many patients: retinacular strain (peripatellar effect) and ELPS (articular effect). A cause‑and‑effect relationship, therefore, can be defined between tilt‑compression (cause) and retinacular strain (effect) or ELPS (effect). Understanding this cause‑effect relationship will help the clinician understand the pathogenesis of articular disruption in patients with chronic patellar tilt (with or without associated subluxation). Pure subluxation (without associated tilt) is less common and creates a clinical‑pathologic picture of instability. Subluxation will be discussed in Chapter 9. Nonetheless, subluxation is often associated with tilt, so there may be factors of both excessive compression (tilt) and patellar instability (subluxation) in some patients.
Inside Chapter 8: