Causes of Full-Thickness Chondral Fissuring of the Knee
Full-thickness chondral fissuring of the knee occurs primarily from rotational injuries or direct blows to the knee, most commonly affecting the medial femoral condyle in young adults. 1
Primary Traumatic Mechanisms
Acute trauma is the predominant cause:
Rotational injuries to the knee joint represent the most frequent mechanism, particularly in young adults, resulting in shearing forces that disrupt the articular cartilage down to the subchondral bone 1
Direct blows to the knee produce focal impact forces that create stellate or scooped-out defects in the articular cartilage, distinguishing these injuries from the linear fractures seen with rotational mechanisms 1
These injuries create a distinct clinical entity separate from osteochondral fractures, as they involve only the cartilage layer without disrupting the underlying subchondral bone 1
Anatomic Distribution Patterns
The location of chondral fissures follows predictable patterns:
The medial femoral condyle is the most frequently affected site in traumatic cases, accounting for 32.2% of isolated full-thickness lesions 1, 2
The patellar articular surface represents the single most common location overall at 37.5% of cases, likely reflecting both traumatic and degenerative mechanisms 2
These focal, contained lesions typically measure less than 4 cm² when they remain isolated and symptomatic enough to warrant surgical intervention 3, 4
Degenerative and Secondary Causes
Progressive cartilage degeneration contributes to fissuring through several pathways:
Untreated or inadequately managed chondromalacia progresses to full-thickness defects over time, as the initial softening and fragmentation (Outerbridge grades 1-2) advances to complete cartilage loss (grade 4) 5, 4
Femoroacetabular impingement (FAI) and similar mechanical abnormalities create repetitive abnormal loading patterns that produce acetabular and femoral chondral defects, with cam-type FAI being particularly associated with grade 4 lesions 3
Inverted labrum pathology has been identified as a causative factor in some cases of hip osteoarthritis with associated grade 4 acetabular chondral lesions, suggesting similar labral pathology may contribute to knee cartilage injury 3
Clinical Presentation and Diagnostic Considerations
Recognition requires understanding the clinical mimicry:
Chondral fractures clinically mimic meniscal tears with joint line pain, swelling, and mechanical catching symptoms, and may occur with or without concomitant meniscal pathology 1, 6
Routine radiographs show no abnormalities in isolated chondral fractures, unlike osteochondral fractures which demonstrate bony involvement, necessitating arthroscopy or arthrography for definitive diagnosis 1
The prevalence of isolated full-thickness (Outerbridge grade 3-4) chondral lesions is approximately 5.2% of all patients with diagnosed cartilage pathology at arthroscopy 2
Important Caveats
Several factors complicate the understanding of chondral fissure etiology:
The natural history remains unpredictable and poorly understood, with some patients remaining asymptomatic despite full-thickness defects while others develop progressive degenerative changes 2, 7
Bipolar ("kissing") lesions indicate more severe pathology with opposing cartilage surfaces both damaged, suggesting either high-energy trauma or advanced degenerative disease 8
In pediatric populations, osteochondritis dissecans (OCD) represents a distinct cause of full-thickness cartilage defects that requires different management algorithms based on skeletal maturity 8