Cartilage and physis mnemonic recap

STR keeps the three unmineralised articular-cartilage zones in order: superficial, transitional and radiate.

The superficial, or tangential, zone has small, flattened chondrocytes parallel to the joint surface. Cells become rounder in the transitional zone. In the radiate, or deep, zone, larger cells align roughly perpendicular to the surface. The tidemark separates these zones from calcified cartilage below. Fluid-film lubrication helps opposing surfaces glide, particularly at low loading rates.

For the growth plate, REPS PER HOUR cues Resting, Proliferative and Hypertrophic. Read from the epiphyseal side toward the metaphysis. Resting cells form the reserve. Proliferating chondrocytes divide and line up like stacks of coins. Hypertrophic chondrocytes enlarge. Matrix then mineralises in the zone of calcification. Ossification follows as vessels enter and osteoblasts lay woven bone onto the calcified scaffold.

The two sketches answer different questions. STR describes layers in articular cartilage. REPS PER HOUR starts the growth-plate sequence, followed by mineralisation and ossification.

References

Chris Wood's original mnemonic study note; Johnston & Tobias, Veterinary Surgery: Small Animal, 2nd ed., Chapters 38-39, Figs.38.9 and39.30 (supplied PDF pp.1532-1534 and1584-1585).