chapter 11: Articular Cartilage Lesions in Patellofemoral Pain Patients
LATERAL PATELLOFEMORAL ARTHROSIS
This form is by far the most common. It is predictable, given the lateral predominance of the patellofemoral joint, the lateral vector of force resulting from the physiologic valgus and the prevalence of lateral tilt in patients with chronic malalignment. Chronic lateral tilt, with or without subluxation often leads to lateral facet erosion. The lateral facet shows the greatest incidence of wear both clinically and in autopsy series (23, 34, 53, 79).LATERAL BICOMPARTMENT ARTHROSIS
The patella contact area extends on to the portion of the femoral condyle that articulates with the tibia in full extension, particularly the lateral compartment. It is not uncommon to see a combination of lateral arthrosis affecting both the tibiofemoral and patellofemoral compartments. This is particularly true if there is associated clinical valgus of the knee. The combination of lateral bicompartment arthrosis is more common in women, likely due to the greater frequency of clinical valgus in this sex (Fig. 11.47).CROSSED BICOMPARTMENT ARTHROSIS
Lateral patellofemoral and medial tibiofemoral compartment arthrosis (Fig. 11.48) are commonly associated. Chronic medial meniscus pathology may cause chronic effusions and diffuse softening of articular cartilage resulting in earlier breakdown of an overloaded lateral facet, particularly in the obese, elderly patient. It is important in such patients to determine if pain is most troublesome in the patellofemoral or medial compartment, so that treatment can be appropriately planned.MEDIAL PATELLAR ARTHROSIS
Severe medial patellofemoral arthrosis is less common than its lateral counterpart. When it does occur, however, it is accompanied by all the radiologic signs that are so common laterally: joint line narrowing, subchondral sclerosis, and cysts (Fig. 11.49). This is in marked contradistinction to the radiographic picture associated with the florid type of chondromalacia encountered in the second and third decades. Medial bicompartment arthrosis is often associated with significant varus deformity. Excessive imbrication of the medial retinaculum at the time of proximal realignment can lead to progressive medial patellar arthrosis (Fig. 11.8).
When dealing with symptomatic arthrosis of the knee, with or without deformity, an axial patellofemoral view is essential. When performing a high tibial osteotomy, this knowledge of the status of the patellofemoral joint may indicate including lateral retinacular release or anterior placement of the distal tibia, after osteotomy, to anteriorize the tibial tubercle.
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