The two main options for surgery are total and partial knee replacements. Various implants and surgical approaches are available, but the best knee replacement option depends on an individual’s situation and needs.
Knee replacements aim to improve functionality and minimize pain for people experiencing knee damage from arthritis or injury. Total knee replacements resurface the entire joint, while partial replacements only resurface one area. The best type of replacement for someone can depend on how much of the knee is damaged.
There are multiple approaches to surgery, including traditional, minimally invasive, and robotic-assisted. A surgeon can also choose from various implants based on ligament stability and other factors, such as deformity, previous trauma, or prior surgery. Therefore, a doctor will evaluate people beforehand and discuss the best replacement options for their unique situation.
This article discusses total and partial knee replacements, surgical approaches, and the different types of knee implants.
A total knee replacement — or total knee arthroplasty — involves replacing the surface of the bones.
The doctor may recommend a total replacement if arthritis is present in multiple areas of the knee and other treatments have proved ineffective. People of all ages can have knee replacements, but doctors may advise someone to avoid high impact activities in the years following surgery.
According to the American Academy of Orthopaedic Surgeons (AAOS), total knee replacement typically involves four basic steps. The surgeon will:
- Prepare the bone by removing damaged surfaces and a small amount of underlying bone.
- Position the implants that recreate the surface of the joint.
- Optionally resurface the patella, or kneecap.
- Insert a spacer between the components.
After the procedure, a person usually stays at the hospital overnight or for a few days. A doctor may prescribe pain-management medications and measures for blood clot prevention. Physical therapy typically follows surgery, with people encouraged to continue exercising at home.
Some individuals may be able to go home on the same day, provided they do well with physical therapy and pain is well-managed.
People typically resume daily living activities 3–6 weeks postsurgery and can drive 4–6 weeks postsurgery. Full recovery and return to more intense activity can take several months or longer. Recovery rates vary for each individual, so following a doctor’s instructions is essential.
- fracture or dislocation
- component loosening from osteolysis (bone degeneration)
- blood clots and associated conditions
- nerve or blood vessel injury
A total knee replacement can be an effective procedure that produces good results in the right person. The AAOS states that 15 years after surgery, 90% of modern total knee replacements are still working well.
Learn more about recovery after total knee replacement surgery.
A partial or unicompartmental knee replacement — or partial knee arthroplasty — involves resurfacing only part of the knee. There may be an overlap in the procedure, management, and risks of a total knee replacement.
A doctor may recommend a partial replacement if symptomatic arthritis is only in one area of the knee and other treatments have not produced the desired results.
After inspecting the joint to confirm the partial replacement, a surgeon will usually perform the following basic steps:
- Prepare the bone by removing cartilage in the damaged area.
- Measure the bone size and positions the implants.
- Insert a spacer between the components.
After the procedure, a person will be discharged or may have to stay overnight. People may be able to put weight on their knee immediately. Doctors can prescribe pain-relief medications and treatments to prevent blood clots. They may also recommend rehabilitation exercises for the person to perform at home.
A partial replacement differs from a total knee replacement in some ways. This includes:
- being typically less painful
- a lower risk of infection
- usually less blood loss
- a quicker recovery
People typically resume daily living activities within 6 weeks after the surgery.
In addition to anesthesia risks, possible complications include:
- blood clots
- need for additional surgery
- nerve or blood vessel injury
Learn more about partial knee replacement surgery.
There are various approaches to knee replacement surgery, including traditional, minimally invasive, and robotic-assisted.
In the traditional approach, a surgeon makes a bigger incision over the knee that exposes the joint.
Minimally-invasive approaches disturb less tissue, involve a shorter incision, and minimize muscular and blood vessel damage. They aim to reduce pain and swelling as well as speed up recovery time. Three types of minimally-invasive approaches are midvastus, subvastus, and quadriceps-sparing.
As with all surgeries, minimally invasive procedures also carry a risk for complications. A surgeon can inform a person about the risks and benefits on a more individual basis.
Robotic-assisted surgery uses 3D planning, computer navigation, and special robotic tools to perform the procedure. This approach can offer greater precision and fewer errors. However, robotic-assisted surgery may require a person to have extra imaging and carries the potential risk of bone fracture.
There are different types of total knee replacement implants,
- Nonconstrained or cruciate-retaining implant: This aims to preserve the posterior cruciate ligament (PCL) and helps maintain the knee’s natural structure as much as possible. Ligaments
help connecttwo bones, and the PCL can help provide stability. However, the anterior cruciate ligament may require removal.
- Semi-constrained or posterior-stabilized implant: This is necessary when the PCL is removed or damaged and cannot provide stability.
- Constrained or “hinged” implant. This has a fitted mechanism that helps provide stability. It may be necessary to have constrained implants in the following situations:
- the medial and lateral ligaments lack stability
- a person has a bone condition
- there is bone misalignment
In a partial knee replacement, a surgeon may use unicompartmental implants, which are smaller.
Knee implants can also be mobile-bearing or fixed-bearing. Mobile-bearing implants enable more rotation than fixed-bearing implants.
Implants can differ in how a surgeon secures them. In the cemented technique, they use a synthetic adhesive to secure the implants in place. In the cementless approach, a surgeon presses the implants on the bone, and the bone grows onto the parts. Sometimes, a surgeon may use a combination of the two.
A doctor will help people choose the best implant and fitting technique for their unique needs.
Total and partial replacements are the main types of knee replacement options. A total replacement involves resurfacing the whole joint, usually for people with damage in two or more parts of the knee. A partial replacement resurfaces only one area of the knee and is generally for people with localized damage.
Partial replacements can offer quicker recovery, less blood loss and pain, and a lower risk of infection than total replacements.
Surgical procedures may differ. While the traditional approach uses a larger incision, minimally-invasive surgery involves a smaller incision and less muscular and vascular damage. Various implants are available based on a person’s ligament stability and other factors. A surgeon can help someone determine the best type of knee replacement options for them.