The human knee: A window on the microvasculature.

Area of Science:

• Orthopedics
• Physiology
• Biomedical Engineering

Background:

• Synovial joints lack tight junctions and basement membranes in lining cells.
• Synovial fluid is continuous with synovial intima interstitial fluid.
• This anatomical feature allows for direct microvascular studies via arthrocentesis.

Purpose of the Study:

• To review 40 years of quantitative microvascular function studies in human knees.
• To examine solute diffusion, blood flow, and lymphatic drainage.
• To assess endothelial pore size and permeability in synovial joints.

Main Methods:

• Quantitative studies of microvascular function in unanesthetized human subjects.
• Analysis of bidirectional fenestral diffusion of small solutes.
• Gel filtration chromatography of paired synovial fluid (SF) and serum (S) samples.

Main Results:

• Established methods for studying microvascular function in vivo.
• Quantified transport of small solutes across the synovial microvasculature.
• Characterized lymphatic drainage and endothelial permeability in synovial joints.

Conclusions:

• Synovial joint microvasculature can be quantitatively studied in humans.
• These studies provide insights into fluid dynamics and solute transport in joints.
• Findings are relevant for understanding joint health and diseases like arthritis.