An amputation is the surgical removal of part or all of a limb. It is usually reserved as a last resort, but can be performed in cases of vascular disease, diabetes and trauma.
Arthritis is a condition which affects the surfaces of joints (i.e. the cartilage) and wears it down until it no longer moves as smoothly as it used to, and no longer cushions the joint.
Knee replacement implants can fail for different reasons. They will need revising (replacing) in certain conditions but not necessarily always.
Limb length discrepancy (also known as anisomelia) is where one arm or leg is shorter than the other. Differences in the length of limbs can cause an imbalance in posture and gait leading to chronic pain.
A non-union fracture, also known as a non-healing fracture, occurs when a broken or fractured bone does not heal.
Osteomyelitis is a serious infection of the bone, and requires treatment with antibiotics and in some cases surgery.