[On the morphology of the hyalin cartilage under immobilization and remobilization (author's transl)]

Structural degenerative changes in the hyaline cartilage of joints induced by immobilization are well known. To find out whether these changes are reversible, the right knee-joint from rabbits was immobilized by extra-articular fixation for 2 or 4 weeks, respectively. In 8 animals the joints were then remobilized for 6 months. Cartilage of the joints was investigated by light microscopy, scanning- and transmission electron microscopy. Already after 2 weeks of immobilization changes in the superficial layer of the cartilage were obvious; after 4 weeks all components of the cartilage tissue were involved in a degenerative process. These changes progressed in the 6-month period in which the joint was remobilized. At the end of the experiment the morphology of the cartilage tissue was comparable to the structural aspect of a typical arthrosis. It is concluded that an external immobilization of a joint which comprises also a pressure on the surface of the cartilage cannot be considered as a harmless procedure. It is recommended to be very cautious with the indication of a therapeutical immobilization of a joint and, if necessary, to use it as short as possible.