Partial versus Total Knee Replacement
If you are a candidate for a knee replacement, why not opt for an easier, less invasive approach that can alleviate pain and result in a quicker recovery? This is a valid question and drives the ongoing interest in partial knee replacement, also known as “unicondylar” or “uni”. This page highlights how partial replacement may be appropriate for a select minority of patients but may not be the best long-term solution compared with total knee replacement for many.
What is a partial knee replacement?
The knee can undergo arthritic degeneration in one or more of the three sections (compartments). These compartments are the inner (medial), outer (lateral) and front (patellofemoral). The most common compartment affected by painful arthritic degeneration is the medial compartment. This leads to joint narrowing (“bone on bone”) resulting from cartilage loss of the medial compartment and pain.
Partial knee replacement involves an isolated resurfacing (replacement) of the involved medial compartment. While replacements of the lateral and patellofemoral compartments have been described, they are less frequently performed in a very small subset of patients due to concerns about survivorship and deformity that cannot be corrected.
Who is a candidate for a partial replacement?
The debate of optimal candidacy for partial replacement is ongoing. Generally, as arthritis is worse, the joint is stiff or deformed (crooked), the ligaments are imbalanced, or the patient is heavier or highly active, there may be reason to avoid partial replacement. If a patient has normal motion in the knee with intact ligaments and isolated (unicompartmental) arthritis, he or she may be a candidate for partial replacement, however there are risks with the longevity of the implant which should be carefully considered prior to having this procedure.
How long will the partial replacement last?
Patients younger and more active are more likely to have an early failure of the implant requiring revision to a total knee replacement in their lifetime(1). While a group of these partial replacements will require revision in 7 to 10 years, some will last 15 years or more(1). Could the second revision procedure have been avoided had the knee just been replaced with a total the first time? We know that most modern total knee replacements will never require revision(1).
The longevity of the partial replacement may also depend on surgical factors. Any subtle imperfection of the alignment of the partial replacement may shift the load of impact to the other sections of the knee, leading to accelerated arthritis progression in those other sections(2).
If the partial replacement fails, what kind of surgery is that?
An important factor about the decision to have a partial replacement is whether future surgery to revise the partial to a total is more complex and fraught with inferior outcomes than a well done primary total knee replacement. This does seem to be the case(2,3). Converting a partial to a total knee replacement comes with loss of bone and sometimes ligaments, often requiring constrained implants, cones, augments, or stems which adds complexity to the procedure(3). For these reasons, revision of a partial replacement has a higher rate of complications and inferior outcomes compared with primary total knee replacement(3). Some evidence suggests revising a partial replacement may be equally fraught with as much uncertainty and complexity as revising a total knee replacement which is considered a major operation(2).
Living with a failed or failing partial replacement can be a challenge. Sometimes by the time that happens the patient is older, may have comorbidities that make a major surgery risky or impossible. Some of these older patients have to struggle with a decision to revise a failed knee implant or live with the problem.
Predicting your results with any surgery requires nuance and individualizing the decision to your unique factors. Partial knee replacement can be a great option in some patients with a comparatively easy recovery. It may not be the best decision for everyone however.
Schedule an orthopedic appointment
If you in need of knee replacement surgery schedule an orthopedic subspecialist evaluation with knee surgeon Dr. Thomas Obermeyer. Dr. Obermeyer provides expert orthopedic care for patients suffering knee osteoarthritis. Dr. Obermeyer has orthopedic offices in Schaumburg, Bartlett, and Elk Grove Village, Illinois. Dr. Obermeyer regularly sees patients from throughout Illinois including Hoffman Estates, Palatine, Elgin, Streamwood, Arlington Heights, and Roselle communities.
- van der List JP, Chawla H, Zuiderbaan HA, Pearle AD. The Role of Preoperative Patient Characteristics on Outcomes of Unicompartmental Knee Arthroplasty: A Meta-Analysis Critique. J Arthroplasty. 2016 Nov;31(11):2617-2627. doi: 10.1016/j.arth.2016.04.001. Epub 2016 May 9. PMID: 27172863.
- Leta, Tesfaye H. MPhil; Lygre, Stein Håkon L. PhD; Skredderstuen, Arne MD; Hallan, Geir MD, PhD; Gjertsen, Jan-Erik MD, PhD; Rokne, Berit PhD; Furnes, Ove MD, PhD. Outcomes of Unicompartmental Knee Arthroplasty After Aseptic Revision to Total Knee Arthroplasty: A Comparative Study of 768 TKAs and 578 UKAs Revised to TKAs from the Norwegian Arthroplasty Register (1994 to 2011). The Journal of Bone and Joint Surgery 98(6):p 431-440, March 16, 2016. | DOI: 10.2106/JBJS.O.00499
- Chou DT, Swamy GN, Lewis JR, Badhe NP. Revision of failed unicompartmental knee replacement to total knee replacement. Knee. 2012 Aug;19(4):356-9. doi: 10.1016/j.knee.2011.05.002. Epub 2011 Jun 1. PMID: 21636281.
At a Glance
Dr. Thomas Obermeyer
- 15+ years of training and experience treating complex shoulder and sports medicine conditions
- Expert subspecialized and board-certified orthopedic care
- Award-winning outstanding patient satisfaction scores
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