Risks of Total Knee Replacement

1. Infection
(1.0% in first time knees, 2-5% in revisions, higher in immune compromised  patients)
SYMPTOMS:  Pain, swelling, redness, drainage, fever
CAUSE: bacteria entering wound either at surgery or later via blood stream
TREATMENT:  If detected early, within several months, and implants are well fixed, an attempt is made to surgically debried the knee, retain the prostheses and treat with intravenous antibiotics for six weeks.
If not detected early, the implants are loose or the infection is recurrent, the implants are removed, intravenous antibiotics are used for six weeks or longer, and the prosthesis is then reimplanted.  In severe cases it may not be possible to reimplant.
PREVENTION:  Many efforts are used to minimize the risks of infection:  prophylactic antibiotics, use of a “laminar air flow” operating room and use of body exhaust suits by the surgical team.
                
2. Loosening
(First time knees:  approximately 3% in first ten years, 10% by 15 years and
20- 30% by 20 years)
HIGH RISK CASES:  Young (< 65 years old), very active patients.  Revision cases have higher risk of loosening.
SYMPTOMS:  Weight bearing pain.
CAUSE: Cemented Knees:  debonding of implant from cement, cement cracking and loss of fixation at the cement bone interface due to poor cement technique or osteolysis
(see below item #9)
Cementless Knees:  Failure of bone attachment to the implant or loss of bone support due to osteolysis.
TREATMENT: Revision surgery.
PREVENTION: Efforts to decrease wear and therefore osteolysis, as well as efforts to improve bonding of cement or implant to bone.

3. Restriction of Motion 
(< 10% cannot flex > 900, <5% cannot flex >750 )
SYMPTOMS:  Persistent flexion contracture results in walking with knee bent; may cause pain.  Lack of flexion over 900 restricts ability to arise from chair, problems with stairs and difficulty with public transportation, sitting in theater or church.
CAUSES:  Scar tissue formation, pain inhibiting early motion.
TREATMENT:  Manipulation under anesthesia, physical therapy.
PREVENTION:  Early motion (active/passive) to at least 700 in the first week after surgery, and at least 900  by 2-3 weeks.

4.Intraoperative Fracture of Bone 
(< 1% in first time cemented knees, < 5% in revision cases)
CAUSES:  Poor bone quality, anatomic variation, difficulty of removal of well fixed implants in revision surgery.
TREATMENT:  fixation of the fracture with wires, cables, screws, plates and/or bone grafts.

5. Intraoperative Damage to Blood Vessels, Nerves and Other Soft Tissues 
(< 1%)
CAUSES:  Stretch, direct injury from surgical tools or implants.
RESULT:   Severe.  If a blood vessel, may cause loss of circulation to limb resulting in amputation or excessive blood loss which can be life threatening.  If a nerve, can result in loss of feeling or function of the extremity possibly on a permanent basis.
TREATMENT:  Surgical repair may be necessary.

6.Blood Clots 
(With prophylaxis risk of clinically detected blood clot is <10% and
risk of pulmonary embolus is <2%, fatal pulmonary embolus is 1 in 5000).
SYMPTOMS:  Blood clots: swelling in lower leg not relieved by elevation, pain in calf.  Embolus  (clot going to lung): shortness of breath, chest pain/tightness.
CAUSE:  Increased state of coagulation of blood post surgery, decreased ambulation, decreased mobility.
TREATMENT:  Hospitalization with intravenous and oral anti-coagulation.
PREVENTION:  Use of prophylactic agents such as blood thinners, pneumatic compression stockings, exercises, early ambulation, spinal or epidural anesthesia.
                                                                                                                                         
7. Instability (> 5%)
SYMPTOMS: buckling, giving-way, pain.
CAUSE:  Imbalance of ligaments, poor patellar (knee cap) tracking or soft tissue entrapment.
TREATMENT: Muscle strengthening, bracing, possible surgery.

8. Patella Fracture (<1%)
SYMPTOMS: Weakness, pain
CAUSE:  Reduced blood supply to patella and/or increased bone stress following total knee.
TREATMENT:  If acute: surgery.  If chronic: immobilizer initially, then physical therapy.

9. Osteolysis bone loss around implants
(< 5% in first 10 years, 10% by 15 years, 30% by 20 years.  Much higher in high risk patients: young, active and overweight)
SYMPTOMS: None until very severe.
CAUSE: Particulates of polyethylene, metal or cement dissect between implant and bone resulting in cellular reaction and bone resorption.
TREATMENT: If detected early, observation with decreased activity, possible surgical debridement with change of polyethylene liner.  If detected late, probable revision of implants.
PREVENTION: Avoid excessive high risk activities.

10. Decreased Bowel Function in early Post-Operative Period 
(common, but complete shut down - so called “ileus”-  is < 5%).
CAUSE:  Pain medications, decreased mobility, anesthesia, “stress of surgery”.
TREATMENT:  Laxative, stool softener, enema (rarely).  If entire bowel shuts down (“ileus”), remove food, IV fluids, possible naso-gastro suction.  Rarely abdominal surgical decompression.
PREVENTION: Stool softener, laxatives, early mobilization.

11. Post Operative Transient Confusion/Disorientation 
(<5%)
CAUSE:  Pain medication, anesthesia medication, pre-existing conditions such as dementia and Alzheimer’s.
TREATMENT:  Decrease or change medications, protection from self-harm, time, return to familiar surroundings.  Usually clears in 2-3 days.
PREVENTION:  Judicious use of pain and other medications.

12. Post Operative Pneumonia 
(< 1% unless pre-disposed due to chronic lung problems)
CAUSE:  Decreased ventilation.
TREATMENT: Antibiotics and breathing treatment.
PREVENTION: Use of incentive spirometer, coughing/deep breathing, early mobilization.
                                                                                                                                         
13. Early Post Operative Decreased Respiration (< 1%)
CAUSE:  Usually pain medication.
TREATMENT:  Narcotic antagonist medication, oxygen, rarely intubation and respirator.
PREVENTION:  Oxygen, use of oxygen saturation monitor, frequent nursing checks.

14. Heart Attacks and Strokes
(approximately 1 in 1000)
CAUSE:  Stress of surgery on pre-disposed individuals.
TREATMENT:  Care by cardiologist or neurologist.
PREVENTION:  Screening pre-operatively for pre-disposing condition.
                                                                                                   
15. Fat/Marrow Embolism
(< 1% clinically detected)
SYMPTOMS:  Shortness of breath, heart rhythm disturbances, mental confusion, very rarely respiratory failure, coma and death (very rare).
CAUSE: Increased pressure inside the bone during surgical instrumentation causes fat and marrow to be pushed into the venous system going to lungs, heart and brain.
TREATMENT: Oxygen and breathing support.

DISCLAIMER: It is not possible to review all the known risks of total knee replacement surgery.  The foregoing is a discussion of the commonly known risks.