Table 2.

Unfavorable biomechanical conditions about the knee joint and the mechanisms by which they result in relative overloading of the articular cartilage

Unfavorable biomechanical condition	Mechanism of relative cartilage overloading
Malalignment	Abnormal load distribution due to shifting of the center of pressure of the tibiofemoral force, resulting in locally increased stresses on the articular cartilage
Loss of meniscal tissue	Alteration in load transmission, resulting in increased peak local stresses on the articular cartilage
	(Partial) loss of secondary constraint to anteroposterior translation in unstable (i.e. anterior cruciate ligament-deficient) knees
Cartilage lesions	Increased stresses on the lesion rim of diameters greater than 10 mm
	Increased exposure of subchondral bone leading to endplate stiffening and microcracks
Joint instability or ligament laxity	Abnormal load distribution due to shifting of the center of pressure of the tibiofemoral force, resulting in locally increased stresses on the articular cartilage
	Increased translation between articular surfaces, resulting in increased shear stresses on the articular cartilage
Trauma	Cartilage damage due to traumatic impact per se
	Increased metabolic and oxidative stress of chondrocytes, resulting in accelerated chondrocyte senescence