Biomechanical Influence of Cartilage Homeostasis in Health and Disease

Table 1

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

Type of load	Regimen	Model system	Major effect	Reference
Strenuous exercise	Running 40 km/day for one year	Beagle dogs	Decreased proteoglycan content in load bearing regions	[9]
Strenuous exercise	Running uphill on a treadmill for 40 weeks and 20 km/day for 15 weeks	Beagle dogs	Reduced GAG content in the superficial zone and reduced cartilage thickness	[8]
Immobilisation	3 weeks	Adult dogs	Reduction in proteoglycan synthesis	[23]
Rigid immobilisation	11 weeks	Canine knee	Decrease in cartilage thickness	[24]
Post ankle fracture model of partial load bearing	7 weeks	20 subjects with ankle fractures	Cartilage atrophy and reduced thickness in patellae and medial tibia	[27]
Joints are unloaded and restricted in movement	24 months	26 subjects with traumatic spinal cord injury	Progressive thinning of cartilage in the patella, medial tibia and decrease stiffness	[28, 29]
Immobilisation and remobilisation	Initial 11 week immobilisation and subsequent 50 week remobilisation period	Canine knee	Immobilisation caused softening of tissue Remobilisation partially restored biomechanical properties	[34]
Single impact load	15–20 MPa, 24 hrs	Bovine cartilage explants	Cell death and collagen damage	[12]
Impact load with variable peak stress	4.5 to 20 MPa, 24 hrs	Bovine cartilage explants	Apoptosis (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/sec	18 and 24 MPa	Bovine cartilage explants	Reduction in protein biosynthesis and compressive/shear stiffness	[17]
High velocity single impact load	24 hrs	Human and bovine cartilage explants	Matrix inhibition was more pronounced in bovine than human tissue	[13, 15, 16]
Repetitive impact load	5 MPa, 0.3 Hz, 2 hrs	Bovine cartilage explants	Necrosis, apoptosis, followed by collagen and proteoglycan degradation	[19]
Static compression	50%, 24 hours	Bovine cartilage explants	Inhibits proteoglycan synthesis and collagen type II	[20, 21]