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] |