Table 1: Experimental evidence indicating the range of nonphysiological loading modalities in articular cartilage.

Type of loadRegimenModel systemMajor effectReference

Strenuous exerciseRunning 40 km/day for one yearBeagle dogsDecreased proteoglycan content in load bearing regions[9]
Strenuous exerciseRunning uphill on a treadmill for 40 weeks and 20 km/day for 15 weeksBeagle dogsReduced GAG content in the superficial zone and reduced cartilage thickness[8]
Immobilisation3 weeksAdult dogsReduction in proteoglycan synthesis[23]
Rigid immobilisation11 weeksCanine kneeDecrease in cartilage thickness[24]
Post ankle fracture model of partial load bearing7 weeks20 subjects with ankle fracturesCartilage atrophy and reduced thickness in patellae and medial tibia[27]
Joints are unloaded and restricted in movement24 months26 subjects with traumatic spinal cord injuryProgressive thinning of cartilage in the patella, medial tibia and decrease stiffness[28, 29]
Immobilisation and remobilisationInitial 11 week immobilisation and subsequent 50 week remobilisation periodCanine kneeImmobilisation caused softening of tissue Remobilisation partially restored biomechanical properties[34]
Single impact load15–20 MPa, 24 hrsBovine cartilage explantsCell death and collagen damage[12]
Impact load with variable peak stress4.5 to 20 MPa, 24 hrsBovine cartilage explantsApoptosis (4.5 MPa), collagen breakdown (7–12 MPa), sGAG (6–13 MPa), and nitrite release (20 MPa)[14]
High strain rate 0.1 and 1/sec18 and 24 MPaBovine cartilage explantsReduction in protein biosynthesis and compressive/shear stiffness[17]
High velocity single impact load24 hrsHuman and bovine cartilage explantsMatrix inhibition was more pronounced in bovine than human tissue[13, 15, 16]
Repetitive impact load5 MPa, 0.3 Hz, 2 hrsBovine cartilage explantsNecrosis, apoptosis, followed by collagen and proteoglycan degradation[19]
Static compression50%, 24 hoursBovine cartilage explantsInhibits proteoglycan synthesis and collagen type II[20, 21]