The figure is an arthroscopic photo of a microfracture procedure, which creates a reparative tissue best described as fibrocartilage. Microfracture is a marrow stimulation technique where stem cells from the medullary canal are given access to the base of the lesion by making small perforations in the subchondral bone. The rationale for this technique is based on these stem cells differentiating into cells that will produce an articular cartilage repair. However, biopsy findings in animals and humans have demonstrated primarily a fibrocartilagenous repair tissue and not true articular cartilage regeneration. The collagen type found in hyaline or articular cartilage is of the type II variety. Fibrocartilage possesses some type II, but is mostly type I and III cartilage.
Both the Intructional Course Lecture and the textbook by Buckwalter provide an in-depth review of articular cartilage biology and the background for chondral resurfacing techniques.
2. Fibrous tissue is created by fibrocytes and lacks type II collagen.
3. Elastofibroma is a distractor (elastofibroma dorsi is a fibrous tumor with a predeliction for the scapulothoracic joint).
4. Hyaline cartilage is true articular cartilage with predominantly type II collagen. It also has columnar organization and a lamina splendens (which differentiates it from what has been called hyaline-like tissue).
5. Chondromalacia refers abnormal softening of the cartilage and is a common pathologic condition of the the knee.
Buckwalter JA, Mankin HJ: Articular cartilage: Degeneration and osteoarthritis, repair, regeneration, and transplantation. Instr Course Lect 1998;47:487-504
Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 471-488