MSK week 1 part 1

• Normally, chondroitin 4-sulfate is the predominant form, with low levels of Keratin sulfate.
• With age, chondroitin 6-sulfate becomes the predominant form with increased levels of keratin sulfate.

• Capsule: a joint pouch containing synovial fluid.
• Synovium: Tissue that lines the capsule and creates synovial fluid (2cc in each knee).

• Normal: 1-4 mL, clear to pale yellow, transparent, very high viscosity, few WBCs (mostly monocytes), glucose equal to serum. No crystals or cultures.
• Inflammatory conditions: increase volume, cloudy, yellow/green, opaque, low viscosity, low glucose, 10k-20k WBCs/mm3 (mostly neutrophils), positive in gout and CPPD crystals.
• Non Inflammatory conditions: Like normal conditions with increased volume, straw color, slightly lower viscosity (still high), and 500 WBCs/mm3.
• Septic: Like inflammatory conditions, but positive for cultures, and negative for crystals.  Has 50k WBCs/mm3.

• Cell concentration and water content of the nucleus pulposus decrease, making it more dense and stiff.
• The anulus fibrosus inner portion increases with age, the fibrocartilage degenerates, and the outer lamellae become stiff.

• Ligament injury always occurs from excessive tension, and dislocations always include ligament injury:
• Grade I: Pain, no instability
• Grade II: some torn fibers, minimal instability.
• Grade III: completely torn

Strong in tension, weak in compression (like a rope). Mechanical forces depend on the orientation of the force applied.

The ligaments form wavy patterns that will straighten out under low stiffness before stretching at high stiffness. (the non-linear portion of a stress curve where collagen fibers straighten out).

• Osteoblasts will be along the surface.  Osteoblasts become osteocytes after becoming trapped in a lacuna.
• Osteocytes will be in lacunas (white border).
• Osteoclasts will be large multinucleated cells that descended from monocytes.

• The epiphyseal plate has many zones.
• Zone 1: Resting cartilage (epiphyseal end)
• Zone 2: Proliferating cartilage (look for stacked coins)
• Zone 3: Hypertrophic cartilage. (bigger cells)
• Zone 4: Calcified cartilage.
• Zone 5: Zone of ossification (diaphyseal end, near the bone marrow)