International Orthopaedics

, Volume 11, Issue 2, pp 129–133 | Cite as

Fine structural changes in the articular cartilage of the rat's knee following short-term immobilisation in various positions:

A scanning electron microscopical study
  • L. Józsa
  • M. Järvinen
  • P. Kannus
  • A. Réffy


The knee joints of 36 rats were immobilised in a padded plaster cast (18 in the flexed and 18 in the extended position) for 1, 2 and 3 weeks. The femoral articular cartilage was then examined under the scanning electron microscope.

After 1 week's immobilisation in the flexed position, the surface layer of the cartilage showed disruption and the superficial chondrocytes were necrotic. The sites of the necrotic chondrocytes were seen as pits on the cartilage surface. In the animals whose knees were immobilised in the extended position, the changes were not so great in severity or extent. After 2 weeks, more advanced changes could be detected in both groups, but they were more severe in the flexed group.

After 3 weeks the changes in articular cartilage were diffuse in the flexed, but focal in the extended group. Diffuse necrosis of chondrocytes, with pit formation on the surface and disruption and disintegration of the collagen fibres, was seen to some extent in all the animals. In the flexed group the changes extended to the whole weightbearing surface of the articular cartilage of the femur, except the intercondylar sulcus. In the extended group, a superficial fibre network was found without the formation of closely packed collagen fibre bundles, and the changes in the chondrocytes were seen only in localised zones.

The authors suggest that during immobilisation, especially in the flexed position, articular hypoxia occurs due to a decreased amount of synovial fluid, the increased compression of the cartilage surfaces and the increased intra-articular pressure. This causes degeneration and necrosis of the superficial chondrocytes and the superficial cartilage layer.

Key words

Articular cartilage Immobilisation Knee position Scanning electron microscopy 


Les articulations du genou de 36 rats ont été immobilisées dans des plâtres matelassés (18 en flexion et 18 en extension) pendant 1,2 et 3 semaines. Le cartilage fémoral a été ensuite examiné au microscope à balayage électronique.

Après une semaine d'immobilisation en flexion, la couche superficielle du cartilage présente des fissurations et les chondrocytes à ce niveau sont nécrosés. Ces zones de nécrose forment des trous sur la surface articulaire. Chez les animaux dont les genoux ont été immobilisés en extension, les altérations sont moins importantes et moins étendues. Après 2 semaines on peut observer des modifications plus marquées, mais elles le sont davantage dans le groupe immobilisé en flexion.

Après 3 semaines les lésions cartilagineuses sont diffuses en cas de flexion, localisées en cas d'extension. Il existe chez tous les animaux, sur une certaine étendue, une nécrose diffuse des chondrocytes, avec des trous dans la surface articulaire ainsi que des ruptures et des dislocations des fibres collagènes. Dans le groupe en flexion les altérations atteignent la totalité de la zone portante de la surface articulaire du fémur, à l'exception de l'échancrure intercondylienne. Dans le groupe en extension on trouve un réseau de fibres superficielles sans formation de faisceaux de fibres collagènes étroitement serrées, et les modifications portant sur les chondrocytes ne sont trouvées qu'en des zones localisées. Les auteurs pensent que durant l'immobilisation, notamment en flexion, il se produit une hypoxie articulaire due à la diminution de volume du liquide synovial, à l'augmentation de compression des surfaces cartilagineuses et de la pression intra-articulaire. Ceci entraîne la dégénescence et la nécrose des chondrocytes et des couches superficielles du cartilage.


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Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • L. Józsa
    • 1
  • M. Järvinen
    • 2
    • 3
  • P. Kannus
    • 3
    • 4
  • A. Réffy
    • 1
  1. 1.Department of MorphologyNational Institute of TraumatologyBudapestHungary
  2. 2.Department of Clinical SciencesUniversity of TampereTampereFinland
  3. 3.Tampere Research Station of Sports MedicineTampereFinland
  4. 4.Research Unit for Sport and Physical FitnessJyväskyläFinland

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