Usually it is done in cases of chronic knee pain due to degeneration, injury etc and which is not being managed conservatively with help of medications or physical therapy.
Osteoarthritis: This is the age related wear and tear of the joint. The cartilage that cushions the bones of the knees softens and wears away.
Rheumatoid Arthritis :This is a disease in which synovial membrane of the joint becomes inflamed and thickened eventually leading to cartilage loss, pain and stiffness.
Post traumatic arthritis: This can follow a serious knee injury.
The surgery is recommended when
- Severe knee pain or stiffness that is limiting the everyday activity.
- Moderate to severe knee pain in resting day or night.
- Chronic knee inflammation.
- Knee deformity.
- Failure to substantially improve with conservative management.
- Wound infection
- Blood clots
- Implant problems
- Continued pain
- Neurovascular injury
TYPES OF IMPLANTS USED
The implants are not one size fits all. Prosthesis implants vary greatly by design, fixation and material.
TOTAL KNEE IMPLANT COMPONENTS
THE FEMORAL COMPONENT: Made up of metal and curves around the lower end of femur.Also it has a groove which fits in the patella.
THE TIBIAL COMPONENT: It is a flat metal platform with a polyethelyne plastic insert or spacer.
THE PATELLAR IMPLANT: It is a dome shaped polyethylene knee cap.
TYPES OF PROSTHESIS
a) FIXED BEARING IMPLANTS
This is the most common implant. Its is called fixed because the cushion of tibial component is fixed firmly to metal platform base.It provides good range of motion.
b) MOBILE BEARING IMPLANTS
If you are young and more active and or overweight the doctor may recommend a rotating platform or mobile bearing knee replacement, the implants are designed for longer performance.
The difference between fixed and mobile bearing implant is the bearing surface is though both use the same 3 components, in mobile bearing the polyethylene insert in tibial component can short distances inside the metal tibial tray. This rotation allows greater rotation to medial and lateral sides of their knee, rotate but this does require a strong ligament support otherwise chances of dislocation are there,
It replicates rotating, twisting, bending , flexion and stability of natural knee.The locking and unlocking mechanism is quite perfectly mimicked by this knee. But compared to above two knees this implant is less forgiving of imbalance in soft tissues
The PCL is one of the most important ligament to support and stabilize the movement of knee and preventing femur to roll back on top of tibia hen flexed.
PCL substituting: They have raised surface on tibial component cushion with raised sloping cam or post which compensates for missin PCL to give stability.
e) UNICOMPARTMENTAL IMPLANTS
If only one side of knee joint is damaged smaller implants can be used to resurface other side.
f) GENDER SPECIFIC INPLANTS:
Some orthopaedic have recently introduced gender specific implants, considering the geometrical difference between both sexes.
TYPES OF KNEE IMPLANT FIXATION
Cemented prosthesis utilize special kind of bone cement that holds components. This is most commonly used,
Cementless it becomes fixed with bone growth into surface of implant, but recovery takes little longer.
Exercise therapy and Do’s and Don’t’s after a total knee replacement.