65: Knee Chondral Injuries

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CHAPTER 65

Knee Chondral Injuries

Alison L. Cabrera, MD; Kurt Spindler, MD

Synonyms

Loose body of the knee

Chondromalacia of the patella

Articular cartilage disorder

Derangement, internal, knee, unspecified

Osteochondritis dissecans

Chondromalacia of medial or lateral compartments of the knee

ICD-9 Codes

717.6   Loose body of the knee

717.7   Chondromalacia of the patella

718.0   Articular cartilage disorder

719.9   Derangement, internal, knee, unspecified

732.7   Osteochondritis dissecans

733.92  Chondromalacia of medial or lateral compartments of the knee

ICD-10 Codes

M23.40  Loose body in knee, unspecified knee

M23.41  Loose body in knee, right knee

M23.42  Loose body in knee, left knee

M22.40  Chondromalacia patellae, unspecified knee

M22.41  Chondromalacia patellae, right knee

M22.42  Chondromalacia patellae, left knee

M24.10  Other articular cartilage disorders, unspecified site

M23.90  Unspecified internal derangement of unspecified knee

M23.91  Unspecified internal derangement of right knee

M23.92    Unspecified internal derangement of left knee

M93.20    Osteochondritis dissecans of unspecified site

M94.261  Chondromalacia, right knee

M94.262  Chondromalacia, left knee

M94.269  Chondromalacia, unspecified knee

Definition

Chondral injuries are any degree of loss of the normal thickness and structure of articular hyaline cartilage. Chondral damage can occur in any joint, but most of the literature has focused on the knee, which is the focus of this chapter. Outerbridge [1] classified cartilage lesions in 1961, and this remains the current classification used to date (Fig. 65.1). Partial-thickness articular cartilage injuries do not heal but are rarely associated with significant clinical symptoms [2]. Full-thickness cartilage injuries, in which the injury extends to the depth of subchondral bone, may heal in with fibrocartilage, but this type of cartilage has shown inferior biomechanical and biochemical properties compared with hyaline cartilage [2,3]. Large, full-thickness cartilage defects are less likely to benefit from the healing fibrocartilaginous response and frequently will lead to symptoms [2].

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FIGURE 65.1 Outerbridge classification depicted by arthroscopic examples: grade I (upper left): cartilage softening and swelling; grade II (upper right): a partial-thickness defect with fissures on the surface that do not reach subchondral bone or exceed 1.5 cm in diameter; grade III (bottom left): fissuring to the level of subchondral bone in an area with a diameter of more than 1.5 cm; grade IV (bottom right): exposed subchondral bone.

The exact incidence of acute cartilage injury is unknown. In young, active patients who present with a hemarthrosis of the knee after a traumatic event, 5% to 10% are found to have cartilage injury [4]. Many studies have retrospectively reviewed the incidence of cartilage injury after arthroscopy for other injury and found rates ranging from 5% to 11% for full-thickness lesions [5,6]. A study looking retrospectively at 25,124 arthroscopies found a 60% incidence of cartilage lesions [7]. Regarding age differences, the incidence of a localized grade III or grade IV cartilage lesion in patients undergoing arthroscopy ranged from 5% to 7% for patients younger than 40 years and 7% to 9% for patients younger than 50 years [6,7]. These studies included both acute and chronic cartilage lesions. Grade II was the most frequent lesion, seen in 42% [7]. The most common locations were the patellar articular surface (36%) and medial femoral condyle (34%) [7]. Seventy percent of the chondral lesions seen were associated with other injury, with medial meniscus tear (37%) and injury of the anterior cruciate ligament (36%) being the most common [7].

Most authors would agree that progression to osteoarthritis is a concern; however, there is little evidence to date that quantifies the incidence or severity of osteoarthritis after chondral injury. More natural history and outcomes research is needed to better predict a patient’s likelihood of progression to symptomatic osteoarthritis according to the characteristics of the cartilage injury.

Symptoms

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