chapter 8: Patellar Tilt‑Compression and the Excessive Lateral Pressure Syndrome (ELPS)
Signs and Symptoms
One group of physical findings needs to be underscored and enlarged. With the normal knee fully extended and the quadriceps relaxed, there is passive medial and lateral "play" of the patella (Fig. 8.1). This passive movement shows a certain amount of individual variability, but it is usually approximately a centimeter in each direction and may be more. Examining knees for this play will provide an appreciation for the normal limits. Examination of the sound knee provides useful comparison. One should remember, however, that both knees may be abnormal even though only one is symptomatic. This medial and lateral movement is limited by the retinacula, particularly the meniscopatellar and patellofemoral ligaments, reinforced laterally by the fascia lata. It is common to sublux the patella passively in a lateral direction during physical examination, searching for evidence of instability or signs of apprehension. One should also displace the patella in a medial direction, searching for excessive lateral tethering. The quality of the retinacula can be appreciated by palpation. This is done best by subluxing the patella toward the side to be palpated, much as would be done to palpate the facet, but this time paying attention to the quality of the respective retinacular ligaments.
As far as the tilt‑compression syndrome is concerned, there are two major patterns: (1) Transverse play is markedly reduced due to global capsular thickening and retraction. This finding is more common in reflex sympathetic dystrophy. (2) Transverse play is restricted in comparison to the sound side. This may be in either or both directions, but it is most commonly a restriction of medial displacement. In this group, lateral retinacular pain is fairly common. Such restriction may or may not be associated with patellar subluxation.
The patient with patellar tilt‑compression may complain of generalized anterior knee pain. On careful clinical examination, however, tenderness in the lateral retinaculum (2, 3), particularly where the vastus lateralis tendon interdigitates with the proximal lateral retinaculum, may be noted. This is common in the younger patellofemoral pain patient who has not yet developed significant articular cartilage erosion. Tightness of the lateral retinaculum perpetuates the problem and can be evaluated objectively, with experience, by raising the lateral edge of the patella past the horizontal plane, with the knee supine (4, 5). Meanwhile, some medial peripatellar tenderness may be present, most likely related to medial stretching and imbalance or medial facet breakdown caused by the lateral tilt condition. This may be particularly prominent in those patients with subluxation in addition to tilt.Although rehabilitation may improve patellar balance through vastus medialis obliquus (VMO) strengthening and stretching of the quadriceps and lateral retinaculum, some tilt‑compression patients will manifest articular changes with ELPS (6), including distal medial patella degeneration, presumably related to deficient contact pressure on this medial articular cartilage as the tilted patella enters the trochlea from full extension, such that there is only lateral contact. By the time the medial patella is pulled into the trochlea, the contact zone has shifted onto more proximal articular cartilage. Chronic patellar tilting, with associated retinacular shortening, can lead to considerable lateral facet overload and deficient medial contact pressure. Eventually, then, many patients with tilt‑compression syndrome will manifest crepitation in the patellofemoral joint, which is truly articular. Some patients will develop effusion related to release of free proteoglycan in the joint, and loose bodies may occur. Once the tilt‑compression patient manifests signs of intra‑articular disease, it is likely that ELPS has developed. Climbing stairs may become particularly difficult; crepitation is frequently noted, and physical activity is limited. Retinacular pain may accompany the articular problems, and may even be the predominant source of pain. By this time, if the patient has had chronic retinacular pain, a pattern of small nerve injury in the painful retinaculum may be found if the segment of painful retinaculum is sent for Gomori's trichrome stain and evaluation by a pathologist (3).
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