Knee Implants Basics

Knee replacement surgery involves removing the diseased components of the knee joint and replacing them with an artificial implant. The knee has three compartments: a) medial b) lateral and c) the patella or the knee cap. Of these, the medial compartment is most prone to osteoarthritis followed by the lateral component.

Partial Knee Replacement Implants and Total Knee Replacement Implants

Depending on how many components are diseased, the surgeon may recommend either a partial knee replacement surgery or a total knee replacement surgery.  If only one compartment of the knee has osteoarthritis, then the surgeon may perform a partial knee replacement surgery which involves removing only the diseased compartment. This may have a host of benefits such as faster recovery for the patient, less blood loss and bone conservation. However, if the other components eventually become diseased, then the patient will have to go in for another surgery.

Total knee replacement involves removing all three components of the knee. The knee implant used in the two surgeries differs (as shown in the pictures below).

Partial & Total Knee Implant

Fixed Bearing Implants and Mobile Bearing Implants

Fixed Bearing Implant

The two parts of the knee that glide over one another when the knee is in motion is called the bearing surface. Fixed bearing implants are very common especially amongst the elderly and less active. In this design, the tibial component is attached to the metal implant underneath. This provides a cushioning for the femoral component.

Knee implants with fixed bearing are vulnerable to excessive weight and may wear down due to the same. Similarly, if the patient has a very active life, then a fixed bearing implant may loosen. The fixed bearing implant is ideal for elderly patients in the normal weight range with less active lifestyles.

Mobile-Bearing Implant

Mobile bearing implants also have three components, however with the difference that the tibial component is not attached to the metal implant underneath and can rotate short distances. The soft tissues and ligaments surrounding the knee, provides the knee with some additional support as compared to a fixed bearing implant. 

Mobile bearing implants are often prescribed in the cases of younger, healthier patients who are looking to achieve greater degrees of rotation.

Mobile bearing implants may be more expensive.

High Flexion Technology Implants

High flexion technology is relatively newer technology enabling patients to achieve a higher degree of flexion. Flexion enables us to carry out activities such as kneeling, climbing stairs and squatting, which is relatively unfeasible with traditional knee implants. If the patient wishes not to be restricted and aims to bend and flex their knee as much as possible, they should convey the same to their orthopedic surgeon so that he can look at deep knee high flexion knee implant options.

High flexion knee implants are known to allow the knee to bend up to 155 degrees. However, it is important to understand that the level of flexion achieved by a patient is dependent on several factors including patient selection, physiotherapy and the quality of the same and surgical technique in addition to the implant selection.

 

Important Safety Information: The performance of knee replacements depends on age, weight, activity level, and other factors. There are potential risks and recovery takes time. People with conditions limiting rehabilitation should not have this surgery. Only an orthopedic surgeon can tell if knee replacement is right for you.