According to the American Academy of Orthopedic Surgeons (AAOS), about 581,000 knee replacements are done each year in the United States. Most of these replacements involve the entire knee joint, a surgical procedure called total knee arthroplasty. However, for about 6 to 8 of every 100 people who have arthritic knees, orthopedists may recommend partial knee replacements, also called unicompartmental knee arthroplasty, or partial knee resurfacing, instead.
General Reasons for Knee Replacement
Knee replacement surgery---whether total knee or partial knee replacement---is frequently considered for people with degenerative osteoarthritis in their knees, or those who have suffered a knee injury with long-lasting consequences. However, not everyone with knee problems is necessarily a candidate for such a surgery because it is a complex procedure and also requires a commitment to rehabilitation. The AAOS suggests several reasons why knee replacement may be a good choice: unremitting pain, whether sitting, standing or lying down, which doesn't get better with conservative treatment such as physical therapy and drugs; inability or poor ability to carry out everyday activities, including walking and stair-climbing, even while using an assistitive device such as a cane or walker; and deformity of the knee joint, especially if it is getting worse.
Requirements for Partial Knee Replacement
The knee joint has two sections or compartments: one on the inner side of the knee and one on the outer side. Osteoarthritis of the knee usually involves both compartments, calling for a total knee replacement. But sometimes, osteoarthritis only affects one compartment, and knee injuries may also be confined to one compartment. In these instances, only the bony area in the single damaged compartment may need to be resurfaced, so a partial knee replacement would be enough.
While the primary qualification for having only a partial knee replacement is limited joint involvement, the Dartmouth-Hitchcock Medical Center website adds that the ligaments that stabilize the knee, particularly, the anterior cruciate ligament, also must be intact. In addition, the AAOS states that unicompartmental knee arthroplasty is generally recommended for older, more sedentary people who are not overweight, as it isn't as durable as the total knee replacement. However, as noted by a December 2009 University of Washington Orthopedic and Sports Medicine article, joint replacement technology and surgical procedures are developing rapidly, so this surgery may eventually be viable for other patients, as well.
Advantages vs. Total Knee Replacement
The UW Orthopedic and Sports Medicine website points out that partial knee replacements for those who qualify, require smaller incisions and do less damage to the muscles and tendons surrounding the knee, leading to shorter hospital stays and quicker healing times. According to the Duke-Hitchcock Medical Center website, another advantage is reduced blood loss. While recovery time is dependent on the participation of the person having a knee joint replaced, people having unicompartmental surgeries, in general, recover more quickly. Finally, because some of the knee joint is left intact, many patients who have had this surgery say their knee feels more normal.
References
- American Academy of Orthopedic Surgeons: Total Knee Replacement
- AAOS: Osteotomy and Unicompartmental Knee Arthroplasty
- University of Washington Orthopedic and Sports Medicine: Unicompartmental Knee Arthroplasty: A Patient's Guide to Partial Knee Replacement using Minimally-Invasive Surgery Techniques
- Dartmouth-Hitchcock Medical Center: Partial Knee Replacement
