Table 3.

The Polarized Light Microscopy Qualitative Score²⁹

Score	Description
0	Evidence of fiber organization, seen as sparse bright patches throughout the specimen. These patches do not have parallel alignment at the surface of the specimen nor perpendicular alignment in the deep zone (DZ), but are randomly oriented in the specimen.
1	Birefringent tissue of the expected orientation in the DZ with fibers oriented mainly perpendicular (±30) to the cartilage–bone interface and occupying less than ∼50% of the thickness of the noncalcified tissue on average. Little additional evidence of birefringent tissue is apparent, other than randomly oriented patches. Birefringent tissue may have inconsistent thickness and intensity of birefringence across the lateral direction of the specimen. The specimen texture may be smooth, patchy, or granular.
2	Identical to a score of 1 except that the DZ occupies more than ∼50% of the thickness of the noncalcified tissue. Alternatively, a second region of birefringent tissue may be present above the DZ that may have any orientation (parallel to the articular surface, obliquely oriented to the articular surface, or multiple orientations) except for vertical. In this case, the DZ may then occupy <50% of the thickness of the noncalcified tissue.
3	Zonal organization with birefringent tissue in the DZ perpendicular to the cartilage–bone interface (±30), and birefringent tissue at the articular surface that is either aligned parallel to the surface or that has multiple orientations. These two zones are separated by a third nonbirefringent region that is appropriate to the species from which the specimen was taken; for example, in human articular cartilage, it may be a thin nonuniform region that is difficult to distinguish compared with the consistent dark band observed in equine articular cartilage. Alternatively, the two birefringent zones are separated by a birefringent region with orientation that is neither parallel nor perpendicular. Zonal thicknesses are heterogeneous across the lateral direction of the specimen. The specimen texture may be smooth, patchy, or granular.
4	Identical to a score of 3 except that the orientation in the superficial zone (SZ) must be parallel to the surface and the transitional zone (TZ) must be appropriate to the species from which the specimen was taken; for example, in human articular cartilage, it may be a thin nonuniform region that is difficult to distinguish compared with the consistent dark band observed in equine articular cartilage. In addition to these characteristics, each zone should approximate the zonal proportions for the species from which the specimen was taken; for example, in human articular cartilage, the DZ should be the largest, occupying >50% of the total thickness of noncalcified tissue. The transitional and SZs are smaller and the TZ may be larger than the SZ.
5	Displays birefringence patterns of young adult hyaline articular cartilage with distinct, superficial, and deep zones with uniform birefringence, indicating parallel and perpendicularly oriented fibers, respectively, separated by an appropriate TZ. Zonal thicknesses are appropriate for the species and location from which the specimen was taken and are relatively homogeneous across the lateral direction of the specimen. Overall, the specimen birefringence has a uniform smooth texture and is neither granular nor patchy.