The Bone Cartilage Interface and Osteoarthritis

Area of Science:

• Orthopedics
• Biomaterials Science
• Veterinary Medicine

Background:

• Osteoarthritis (OA) is a degenerative joint disease affecting both humans and equines.
• Understanding the microstructural changes at the osteochondral junction is crucial for OA pathogenesis.
• Previous studies on equine and human OA tissue provide valuable insights into disease mechanisms.

Purpose of the Study:

• To review and synthesize findings on the microstructural changes in articular cartilage and subchondral bone in osteoarthritis.
• To elucidate the role of bone resorption and repair processes in the progression of OA.
• To analyze the contribution of specific microstructural features to joint destruction in OA.

Main Methods:

• Re-utilization of tissue samples from prior studies.
• Scanning electron microscopy for high-resolution imaging.
• Novel light microscopy techniques.
• X-ray micro-tomography for 3D structural analysis.

Main Results:

• Overload exercise and rest periods downregulate turnover at the osteochondral junction, predisposing to microfracture.
• Resorption canals, loss of articular calcified cartilage (ACC), and subchondral bone (SCB) cracking are key OA features.
• High-Density Mineral Infill (HDMI) seals cracks, extruding as High-Density Mineral Protrusions (HDMP) into hyaline articular cartilage (HAC), leading to fragmentation and destruction.
• SCB densification with woven bone, HAC fibrillation, eburnation, and repair with abnormal tissues characterize advanced OA.

Conclusions:

• The interplay between bone resorption and repair at the osteochondral junction is a critical driver of OA.
• Microstructural alterations, including HDMI and HDMP, significantly contribute to cartilage and bone destruction in OA.
• This review highlights the complex pathological cascade in OA, emphasizing the need for targeted therapeutic strategies.