Difference Between Total and Partial Knee Replacement
The knee has three compartments—the medial compartment (inside aspect of the knee), the lateral compartment (outside of the knee) and the patellofemoral compartment (in front of the knee). In some knee osteoarthritis patients, only one compartment of the knee is affected—usually the medial compartment. The lateral compartment can be affected, but it is less common.
A partial or unicondylar knee replacement, as its name suggests, replaces only the affected compartment of the knee. On the other hand, a total knee replacement involves the replacement of all three compartments of the knee.
While just one compartment is replaced during partial knee replacement, anterior and posterior cruciate ligaments are preserved. The ligaments are removed in a total knee replacement. Suffice it to say, with a partial knee replacement, more of your own body structure remains intact.
Benefits and Risks With Partial Knee Replacement
There are benefits to having a partial knee replacement as compared to a total knee replacement. The same complications are possible with both surgical procedures: loosening, infection, nerve injury, fracture of the bone and more.
Candidates for Partial Knee Replacement
In 1998, two doctors (Drs. Scott and Kozinn) established criteria for determining which patients were good candidates for partial knee replacement. The ideal patient has these characteristics:
Older than 60 years oldLess than 180 lbsLess activeHas good range of motion before surgeryHas minimal deformity
Patients with inflammatory types of arthritis, such as rheumatoid arthritis, are not regarded as good candidates for partial knee replacement. With inflammatory arthritis, more than one compartment is usually involved.
Recovery and Success Rates
Recovery times vary per person and also depend on general health. Total knee replacement surgeries are typically successful, with at least 90% offering pain relief and about 90% still functional after 20 years.
The data on partial knee replacements is more limited and sometimes complicated by surgeries in those who were not great candidates. Studies do suggest that about 90% of partial knee replacements are functional after 10 years and approximately 70% are functional (no additional surgeries) after 25 years.
Walking and Other Low-Impact Activities
Physical therapy is an important part of the recovery process and can help in restoring mobility for any type of knee replacement.
Some level of walking with assistance is usually possible after a total knee replacement surgery and many can walk on their own within a few weeks. A full return to unlimited low impact activities such as walking, biking, and swimming are often possible within a few months. It may take six months to one year to reach maximum strength and mobility.
Recovery tends to be faster for a partial knee replacement with a full return to activities possible within three to six weeks. However, the majority of knee replacement candidates have more than one area that is damage or diseased, so a total knee replacement is recommended for the best outcomes.
Complications
Serious complications, such as a joint infection, after surgery occur in about 2% of those who have a total knee replacement and may prolong or limit recovery. In some cases, the complication may be so severe that the implant may need to be removed and replaced.
Serious complications are even more uncommon for partial knee replacements, with infections occurring in less 1% of patients.
Bottom Line
There have been improvements in the design of unicompartmental prostheses over the years. Having a surgeon experienced in working with partial knee replacements is a plus too. Ultimately, a successful outcome depends on having the right patient for the procedure. It is estimated, though, that only 6% to 10% of patients are suitable candidates for partial knee replacement.
Cons: Many people are not good candidates for a partial knee replacement. If damage occurs to the other parts of the knee joint, additional surgeries, such as a conversion to a total knee replacement, may be needed later on.
