chapter 8: Patellar Tilt‑Compression and the Excessive Lateral Pressure Syndrome (ELPS)
NATURAL HISTORY OF THE TILT‑COMPRESSION SYNDROME
Patellar tilt‑compression problems may present initially in the early teen years, with anterior knee pain aggravated by physical activities. Such patients have had congenital tilting of the patella that was not clinically apparent earlier in life. With time and longitudinal bone growth, however, the magnitude of stress on a chronically tilted patella may become substantial. The patella that has been chronically tilted, even to a mild degree, may eventually manifest findings consistent with an adaptively shortened lateral retinaculum. If a patella tilts down chronically to the lateral side (Fig. 8.2), the retinaculum becomes short, relative to what is normal. As the size of the patient increases, the vector of posterior pull on this already shortened lateral retinaculum becomes greater with knee flexion, and overload on the lateral retinaculum (which is now tight) may become enough to cause retinacular overload, stretching, and compression of small sensory nerves within the lateral retinaculum, resulting in pain and accentuation of lateral facet compression. Many of the early pain problems experienced by patients with patellar tilt will be most apparent in the lateral retinaculum and peripatellar connective tissue supports. Histologic study of painful retinacular biopsies (3) has shown that fibroneuromatous degeneration of small nerves in the lateral retinaculum is common in patients with chronic patellar malalignment.
As this process proceeds, lateral facet overload and deficient medial facet contact may lead to articular cartilage degeneration on both the medial and lateral facets. Often, the first sign of articular trouble is at the critical zone (Fig. 8.3). ELPS is primarily the result of chronic lateral patellar tilt, adaptive lateral retinacular shortening, and resultant chronic imbalance of facet loads. Although full ELPS may develop rapidly in young patients, it is more commonly found in older patients, particularly female patients, with a long history of anterior knee pain. The chronic lateral facet overload can lead to devastating loss of lateral facet articular cartilage.
In summary, then, the tilt‑compression syndrome will usually proceed through a period of soft‑tissue pain related to adaptive retinacular shortening and eventually lead to patellar arthrosis.
Inside Chapter 8: