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Aseptic loosening is an important problem that causes failure of total knee arthroplasty and its incidence vary from one study to another .

The mechanisms of loosening may be micromotion between component and bone or that the components sink or subside into the bone.

The root cause of failure is mechanical; the stresses on the cancellous bone exceed the strength of the bone tissue, or the stresses at a fixation interface exceed its strength. It could be due to surgical factors, patient factors, or implant design. All these factors act in a complex way to affect the integrity of bone implant system. Periprosthetic osteolysis is another

Surgical factors include surgeon and hospital experience, alignment of the components in all planes, and ligament balance.

Patient factors include: weight, activity, age, gender, bone quality, diagnosis before total knee replacement, previous surgery on the same knee, and preoperative deformity.

Implant design atfects loosening rate according to several factors which include type of prosthesis, material of prosthesis, articular geometry, metal backing, and method of fixation.

Surgeons continue to search for different measures to avoid such a major complication including: improvement in prosthetic material and design, surgical technique, cementation.

Histological study of the cellular mechanism of osteolysis and the elucidation of the roles of OPG and RANKL in the regulation of osteoclastogenesis has provided an ideal drug target to prevent osteolysis.