Ilkka Kiviranta

Indentation study of the biomechanical properties of articular cartilage in the canine knee

Considering articular cartilage to be composed of an elastic organic matrix and interstitial water, compressional stiffness of canine knee (stifle) joint cartilage was determined in the form of shear moduli. Different stresses and indenters were used to reveal the suitability of the indentation measurement with a step-load. We were able to demonstrate the linearity of instant and equilibrium responses of cartilage. Using a theoretical solution for indentation of an elastic layer, the effect of the finite thickness of cartilage on the instant and equilibrium responses was eliminated. Using the intrinsic (equilibrium) shear modulus of the cartilage matrix, the stiffest cartilage was found to be located in the patellar surface of the femur. The thick, proteoglycan-rich tibial cartilage, which was uncovered by menisci, was softer than the opposing femoral cartilage. This finding casts doubt on the suggestion that the concentration of proteoglycans unambiguously determines the stiffness of cartilage, but empha...

Investigation of Articular Cartilage Surface Morphology with a Semiquantitative Scanning Electron Microscopic Method

A semiquantitative scanning electron microscopic method for analysis of the articular cartilage surface morphology was developed. The method was based on a survey of large picture montages (ca. 70 X 100 cm) and classification of the cartilage surface changes at three levels. Computer technique was utilized in the analysis. The method ensured numerical expression and statistical treatment of the results. With this method we investigated the effects of physical exercise and immobilization on the articular cartilage of rabbit patella.

Influences of Joint Immobilization and Running Exercise on Articular Cartilage Surfaces of Young Rabbits

The influences of joint immobilization and running exercise on the articular cartilage surfaces of the patella and lateral tibial condyle of young rabbits were investigated by the semiquantitative stereomicroscopic and scanning electron microscopic methods during a period of 8 weeks. The smoothness of the articular surfaces was disturbed already 1 week after the onset of immobilization. Leafy, slightly rough and rough surface qualities associated with superficial splits were observed. The changes were of the same nature after a longer period of immobilization. Running exercise on the treadmill (150-300 m twice a day, 12-24 min per turn, 5 times a week) led to an increase of the striated surface quality at 1 to-2-week intervals as compared with the controls. It was apparent that during immobilization remarkable changes of the articular cartilage took place within the first week, while running exercise up to 8 weeks elicited only transient or minor alterations of the articular surface.

Effects of Immobilization for 6 Weeks on Rabbit Knee Articular Surfaces as Assessed by the Semiquantitative Stereomicroscopic Method

The effects of a 6-week immobilization period on rabbit knee articular cartilage surfaces were investigated by a new semiquantitative stereomicroscopic method following ink staining and processing for scanning electron microscopy. All surfaces of the immobilized knee joint were affected and displayed significant degenerative alterations. The knee joint contralateral to the immobilized one exhibited slight changes which could be interpreted as a sign of altered loading after immobilization. Articular surfaces of the patella and lateral condyle of the femur proved to be best suited for surface analysis on account of the small size, distinct borders and inherent evenness of the cartilage in non-treated animals.

Semiquantitative analysis of rabbit knee articular surfaces based on stereomicroscopic examination of the cartilage.

A semiquantitative stereomicroscopic method was devised in order to examine rabbit knee articular surfaces. With the aid of a drawing tube mounted on a stereomicroscope, enlarged pictures (magnification of X 14-19) of ink-stained or SEM specimens of joint surfaces were drawn and the structural details classified. The point-counting method or a computer-coupled analyzer was used to analyze the pictures. The data thus obtained underwent statistical evaluation. The method proved to be very useful for the quantitation of experimentally induced changes on cartilage surfaces.

Superficial zone of articular cartilage after immobilization and running training: is proteoglycan depletion the clue to the pathogenesis of osteoarthrosis

Superficial zone of articular cartilage after immobilization and running training: is proteoglycan depletion the clue to the pathogenesis of osteoarthrosis