Infection is a catastrophic and costly complication after total knee arthroplasty. With increased understanding and refinement of TKA techniques, the incidence has decreased from l-23% in the early stages to 1-2% today. According to the extent of involvement, post-TKA infections are classified as superficial infections (not involving the joint system) and deep infections (involving the joint system); according to the onset and course, they are classified as acute or early infections and chronic or late infections. This article describes the risk factors for post-TKA infections and their prevention, diagnosis and treatment as follows. Pre-operative factors of TKA: The formation of periprosthetic epilepsy caused by previous meniscus and synovial surgery or multiple revisions, shrinkage or deformity increases the difficulty of TKA and prolongs the operation time; the patient’s advanced age, poor general condition, diabetes, rheumatoid arthritis treated with corticosteroids, and chronic urinary tract infection are all risk factors of post-TKA infection. Perioperative factors: 1, surgical field skin bacteriology: preoperative skin culture of the surgical area, screening of appropriate antibiotics and skin cleaning techniques can effectively eliminate drug-resistant bacteria and reduce postoperative infections. 2, preoperative prophylactic antibiotics: TKA preoperative prophylactic antibiotics can significantly reduce the incidence of postoperative infections, head hold aspirin and head hold mondo are most commonly used, combined with aminoglycosylated antibiotics if necessary. 3, the surgical environment: closed or with an exhaust pipe surgery in can effectively control and move the body discharged bacteria. 4, surgical factors: TKA need to elevate the resting limb, drive blood on the tourniquet, blocking blood flow, only 1% of the original blood flow through the intramedullary vascular circulation, so significantly reduce intraoperative bleeding, but the resulting state of oxygen resistance to reduce the body’s resistance to microorganisms; drive blood at the same time Capsulotomy, partial or complete removal of the subanatomic fat pad, part of the high light on the lateral vessels and other operations caused by the rolled bone and the peripheral soft tissue blood supply obstruction, making the incision easy to Infection, intraoperative use of skeletal exostosis technology, joint system within the # away from the ligament, sling to protect the blood vessels and other techniques can be prevented. 5, prosthetic factors: antibiotic bone cement can effectively prevent. 6, postoperative drainage of the knee: postoperative drainage of the knee joint can improve the skin and joint cavity environment and reduce the incidence of deep infection. Postoperative factors: The blood of the skin of the periosteal country is mainly supplied by the internal and external femoral vessels traveling from posterior to anterior. Improper selection of the TKA surgical incision can cause blood supply obstruction and low oxygen partial pressure in the incision, which can easily cause superficial infection and can invade deeper; it can be effectively prevented by selecting a suitable incision, gently pulling the soft tissue, carefully stopping bleeding and tension-free suturing; II. Diagnosis of post-TKA infection Diagnosis of post-TKA infection requires comprehensive consideration of (a) Medical history, clinical symptoms, signs and ancillary tests: (i) Medical history: Those who have the above risk factors for TKA. (B) Clinical symptoms and signs: acute or early infection can show fever, systemic symptoms, knee pain, swelling, stiffness, edema, fluid at the incision, rupture, etc., the diagnosis is easier; chronic or late infection has formed a sinus tract is not difficult to diagnose; subacute, low virulence bacteria or occult infection symptoms are not typical, the diagnosis is more difficult, for the appearance of knee pain after TKA should be highly suspicious of infection until the diagnosis is clear. (c) Ancillary tests: 1. routine blood count and sedimentation; 2. bacteriological examination: including incisional swab culture, joint pat aspirate and intraoperative specimen culture or PCR processing; 3. X-ray; 4. radionuclide scan; 5. intraoperative frozen section histological examination intraoperative slide, bone and other tissues frozen section histological examination can help the diagnosis of subacute or occult infection. The goal of treatment of post-TKA infection is to eliminate the infection and achieve a pain-free knee. (ii) debridement with preservation of prosthesis: synovectomy only, debridement of bone and soft tissue without removal of prosthesis and bone cement. (c) Phase I prosthesis reimplantation: remove the prosthesis and all the bone cement, perform a thorough debridement of the bone and soft tissues, remove the plug channel, synovial membrane, necrotic or ischemic tissues, replace the prosthesis with a new one, fix it with antibiotic bone cement, and use autologous or homogeneous bone blocks or lamellar bone grafts for bone loss. (d) Phase II prosthetic reimplantation: the operation includes three stages, 1. removal of prosthesis and bone cement, thorough debridement of bone and soft tissue, placement of antibiotic bone cement beads or spacer cushion joint cavity, closure of the incision. 2.The interval is treated with sensitive antibiotics by parenteral route. 3.After the infection is eliminated, the soft tissue, bone, and extensor device are in good condition, the new prosthetic rest can be implanted and fixed with antibiotic bone cement or antibiotic autologous or homologous bone. (E) Arthroplasty: The infection can be successfully eliminated, the knee joint can be disease-free, and the knee joint can be lost, only for those who have lost the function of the hand-extension device and have serious bone and soft tissue defects that cause reconstruction difficulties. It is divided into phase I and phase II fusion. (vi) Excision and amputation: Excision and amputation surgery includes removal of the prosthesis and bone cement, thorough debridement of the bone and soft tissue, and filling the knee joint with antibiotic bone cement beads. If long-term antibiotic therapy, repeated debridement, antibiotic cement bead insertion and use of local myocutaneous flap graft infection persist, there is intractable pain, infection is life-threatening or intraoperative injury to large blood vessels, then supra-knee horizontal amputation is required. Management of bone loss in primary and total knee revision As with primary total knee arthroplasty, the goal of revision is to restore the joint line to as normal a level as possible and to correct poor anatomic alignment of the joint to obtain satisfactory joint stability and functional status. However, problems such as infection, soft tissue contracture, supporting ligament injury and bone loss associated with multiple knee surgeries can make it difficult to achieve these goals, especially since significant bone loss after TKA can cause loosening of the prosthetic rest, fractures of the non-supporting portion of the implant and periprosthetic fractures. Severe bone loss makes reconstructive surgery difficult. This article provides the above brief description of the mechanisms of bone loss formation after TKA, assessment of bone defects, principles of management, common treatments and their efficacy.