The synovial cavity as a "tissue culture in situ"--science or nonsense?

Acellular freeze-dried canine profundus tendon allografts were placed in the knee joints of dogs and later harvested at 2, 3, and 6 weeks. All allografts remained intact, free swimming, and free of adhesions; all were covered by a layer of proliferating fibroblast-like cells that "healed" cuts made in the allografts, rounded off their previously squared-off ends, and recellularized them. The cell source for the phenomena was the synovial cell of the joint, a highly versatile, facultative fibroblast. An intrinsic capacity of flexor tendons to heal themselves cannot be critically tested by fallaciously considering synovial cavities "tissue cultures in situ," as some investigators have claimed.