The primary reason for the limited repair capacity of cartilage following injury is its low metabolic activity of cartilage cells.

- Cartilage is a specialized connective tissue that is largely avascular, meaning it lacks blood vessels.
- This characteristic significantly limits the supply of nutrients and oxygen to the chondrocytes, the cells responsible for maintaining and repairing cartilage.
- Due to this limited nutrient supply, the metabolic activity of chondrocytes is very low compared to other tissues.
- This low metabolic rate results in slow cell division and minimal matrix synthesis, which severely compromises the tissue’s ability to heal after injury.

- Additionally, since cartilage is encased in a dense extracellular matrix, with a low density of cells scattered within, the capacity for regeneration is inherently restricted. The lack of a direct blood supply means that inflammatory cells and reparative factors cannot efficiently reach the site of injury, resulting in poor healing and often leading to degeneration rather than repair.

The other options are incorrect because:
- Presence of dense fibrous capsule: Cartilage does not have a fibrous capsule; it is primarily surrounded by the perichondrium in some types, but this is not the main factor limiting repair.
- Excessive vascularization impeding healing: Cartilage is actually avascular, so excessive vascularization does not occur.
- High turnover rate of chondrocytes leading to scar tissue: The turnover rate is low, not high, and cartilage usually does not form scar tissue like other connective tissues.

Reference: Robbins Basic Pathology, 10th Edition, Chapter 4: Tissue Renewal, Repair, and Fibrosis