Table 3.

A comparison of animal and in vitro studies indicating the positive effect of physiological joint loading in articular cartilage.

Type of load	Regimen	Model system	Major effect	Reference
Running exercise	6 to 12 km/day	Hamster	Increased proteoglycan content	[26]
Running exercise	15 km over 28 days	Rat OA induced by ACLT	Reduced apoptosis and chondral erosions	[50]
Running exercise	Varied age, 15 months exercise	Rabbit	Improved collagen organisation in young and reversed OA in older animals	[54]
Increased loading	Increased loading following 8 weeks of splinting	Rabbit	Increased maturation of tissue and increased collagen content	[55]
Conditioning exercise	Increased workload by 30%	Foals	Reduced cartilage degeneration index	[56]
Running exercise	4 km/day, uphill, 15 weeks	Beagle dogs	Increased proteoglycan content and cartilage thickness	[53]
Cyclic pressure-induced strain	0.3 Hz, 6 hours	Human and monolayer	Increased aggrecan gene expression	[58]
Hydrostatic pressure	5 and 10 MPa at 1 Hz for durations of 4 h per day for 4 days	Human monolayer	Increased aggrecan and collagen type II gene expression	[59]
Dynamic compression	3% at 0.01 to 1 Hz, 43 days	Bovine and agarose	Increased proteoglycan and collagen synthesis	[63]
Dynamic compression	15%, 1 Hz, 48 hours	Bovine and agarose	Increased cell proliferation and proteoglycan synthesis and reduced nitrite release	[60, 61]
Dynamic compression	10% at 1 Hz, 3  ×  1 hr on, 1 hr off, 5 days/week for 21 days	Bovine and agarose	Increased equilibrium aggregate modulus, sGAG and collagen synthesis	[62]
Dynamic compression	1 MPa, repeated 2 and 4 sec, 1.5 hour	Bovine and explants	Increased proteoglycan synthesis	[64]
Cyclic compression	1 MPa, 0.5 Hz, 3 days	Bovine and explants	Increased proteoglycan synthesis	[70]