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Four women, aged 63 to 90 years old, presented with mildly painful shoulders of decreased mobility or stability. Radiographic evidence of a complete tear of the fibrous rotator cuff was present in 7 of 8 shoulder joints. Microspheroids containing hydroxyapatite crystals were seen by scanning electronmicroscopy in 12 of 13 synovial fluid samples. All synovial fluids showed activated collagenase and neutral protease activity. This constellation of findings represents a heretofore undescribed syndrome which we have designated "Milwaukee shoulder."The shoulder is the most mobile joint in the human body. The glenohumeral joint contributes most to this remarkable range of motion (1). Such mobility has been achieved at the sacrifice of joint stability, which depends largely on the integrity of the fibrous conjoint tendons of the surrounding muscles+ommonly called the rotator cuff (1).

The many years of challenge in treating athletes disabled by tendinitis stimulated a study of the aging of tendons. Autopsy specimens, representing tendons from 20-, 50-, and 70-year-old subjects, were obtained. Each specimen, consisting of a wedge of the greater tuberosity with the attached supraspinatus tendon, was examined roentgenographically to study the morphologic features of the greater tuberosity and was decalcified and stained with Safranin O to evaluate the amount of fibro-cartilage, with van Gieson to identify Sharpey's fibers, and with hematoxylin and eosin to determine cellularity, fiber integrity, and vascularity of the tendon. The comparison related to chronological age documented a morphologic change of the greater tuberosity and progressive degeneration of all elements of the tendinous structures with progressive (1) osteitis of the greater tuberosity, cystic degeneration, and irregularity of the cortical margin; (2) degenerative sulcus between the greater tuberosity and the articular surface; (3) disruption of the integrity of the attachment of the tendon to the bone by Sharpey's fibers; (4) loss of cellularity, loss of staining quality, and fragmentation of the tendon; (5) diminution of the vascularity of the tendon; and (6) diminution of fibrocartilage.

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The healing of surgically induced defects in mature rabbits' hyaline cartilage was examined histologically and biochemically. The subchondral bone underneath the lesion was the source of repair. At the end of the first month, mushroom-shaped chondroid buds were seen sprouting from the subchondral bone. By the tenth week, these buds fused to a cartilagenous plug filling the lesion. The repaired cartilage synthesized Type I1 collagen.