Use Of Unicompartmental Knee Arthroplasty Research Articles

Unicompartmental knee arthroplasty questionnaire (UniQ-study): Unknown is unloved

BackgroundAlmost 50% of the patients requiring knee replacement are suitable for medial unicompartmental knee arthroplasty (UKA). However, national registries have shown a use far below 50%. AimThe aim of this study was to identify the factors that could influence the use of UKA. MethodsA questionnaire was conducted among practicing knee surgeons of the Dutch Orthopedic Association. The questionnaire was classified into three domains: surgeon, patient selection, and professional opinion. Associations between the domains and UKA volume and contra-indications were tested using Pearson’s chi-square tests. ResultsOf the 113 included respondents, 40% had no hands-on exposure during residency. Frequently reported contra-indications were obesity (68%), lateral osteophytes (21%), chondrocalcinosis (20%), and age (20%). Medial partial thickness lesions were considered a contra-indication by 49% and lateral joint space narrowing by 61% of the respondents. Respondents perceived UKA to outperform total knee arthroplasty regarding all outcomes, except survival (1.8% versus 42%). The reported barriers for UKA use were insufficient experience (20%), high revision rates (20%), and low hospital volume (16%), whereas 60% did not experience any at all. Hands-on UKA exposure during residency was associated with an increased use of correct indications. Furthermore, the use of correct indications was associated with an increased UKA volume. ConclusionWe showed a low UKA exposure during residency and considerable variations in contra-indications. These factors may contribute to an underuse of UKA. Improved UKA training could lead to increased experience and better patient selection among surgeons and consequently a higher use of medial UKA.

Reconsideration of the indications for unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty (UKA), a procedure that has gradually emerged in recent years, is considered an effective treatment for resolving knee pain and restoring good function due to its significant clinical advantages. In the 1980s, Kozinn and Scott proposed the classic indications as selection criteria to identify ideal candidates for UKA. However, as treatment concepts, surgical instruments, surgical techniques, and prosthesis designs for this disease have improved, these indications proposed more than 30 years ago appear too limited, leading to some limitations in the widespread use of UKA. Specifically, surgeons have offered new perspectives on issues related to obesity, age, patellofemoral arthritis, severe varus deformity of the knee, anterior cruciate ligament deficiency, flexion contracture, failed high tibial osteotomy and post-traumatic arthritis. For this reason, this article will briefly discuss modern perspectives involving the indications for UKA based on current evidence with the aim of providing a reference for the reader.

Are patients with preoperative synovitis suitable for unicompartmental knee arthroplasty? Magnetic resonance imaging evidence from a retrospective cohort study

BackgroundThe use of unicompartmental knee arthroplasty (UKA) in patients with preoperative synovitis is controversial. This study aimed to investigate the association between synovitis detected by magnetic resonance imaging (MRI) and prognosis after UKA.MethodsSynovitis was graded using the MRI Osteoarthritis Knee Score criteria based on preoperative MRI findings of 132 UKAs performed between June 2020 and August 2021. The Knee Society Knee Score (KS-KS) and the Knee Society Function Score were collected preoperatively and 1 year postoperatively. The relationship between synovitis and the changes in the Knee Society score was analyzed using logistic regression.ResultsUnivariate logistic regression showed that patients with higher preoperative synovitis scores (odds ratio (OR) = 1.925, 95% confidence interval (CI): 1.482–2.500, P < 0.001) had higher KS-KS changes. After adjusting for confounding variables, synovitis was proven to be an independent factor for KS-KS improvement after UKA in multivariate logistic regression (OR = 1.814, 95% CI: 1.354–2.430, P < 0.001). Before UKA, patients with synovitis had lower pain scores (PS) than patients without synovitis (95% CI: -17.159 – -11.160, t = -9.347, P < 0.001). There was no difference in PS between the two groups after UKA (95% CI: -6.559 – 0.345, t = -1.782, P = 0.077).ConclusionsPatients with synovitis can achieve good improvement of pain symptoms, and the efficacy is not inferior to that of non-synovitis patients after UKA.

Consensus statement on unicompartmental knee replacement: A collaboration between BASK and EKS

BackgroundThe aim of this study was to deliver consensus recommendations for the clinical practice of unicompartmental knee arthroplasty (UKA). MethodsMembers of the British Association for Surgery of the Knee (BASK) and European Knee Society (EKS) were invited to attend a joint meeting in London, UK (December 2019). A formal consensus process was undertaken at the meeting incorporating a multiple round Delphi exercise, with group discussion of areas of agreement and disagreement between rounds. Eighty delegates attended the meeting and five consensus statements were considered and revised, with a threshold level of 80% agreement required as the definition consensus. ResultsFive consensus statements with accompanying supporting evidence and text were agreed following two rounds of the process: (1) UKA should be offered as a successful alternative to TKA in patients undergoing arthroplasty who meet agreed indications; (2) When consenting a patient for UKA, information including the benefits and risks that are specific to UKA, should be tailored to and discussed with the individual patient; (3) Evidence suggests that surgeons should avoid low-volume use of UKA to optimise outcomes for their patients; (4) Surgeons should use the contemporary evidence-based indications and contraindications for medial UKA; (5) Knee arthroplasty surgeons should have exposure to and training in UKA. ConclusionsThe agreed joint BASK-EKS consensus statements on UKA practice are recommended as the contemporary basis of optimal care for these patients and should inform future training and service developments.

Midterm Outcomes of Unicompartmental Knee Arthroplasty for the Treatment of Knee Medial Compartment Osteoarthritis: A Retrospective Study.

Many surgeons avoid performing unicompartmental knee arthroplasty (UKA) due to various concerns. Cohort studies showing the satisfactory outcomes of UKA can convince surgeons to use this technique. In this study, we report the mid-term outcomes of UKA in a series of patients with medial compartment knee osteoarthritis. Seventeen patients with unicompartmental degenerative joint disease of the knee that underwent UKA and were available for final evaluation were included. The mean age of the patients was 63 ± 5.1 years. The mean follow-up of the patients was 37.2 ± 18.3 months. The outcome measures were the Oxford Knee Score (OKS), Knee Society Score (KSS) for knee score and knee function, Knee injury and Osteoarthritis Outcome Score (KOOS), knee range of motion (ROM), and satisfaction rate on a 5-point Likert scale. In the last follow-up visit, the mean of OKS and knee score section of the KSS were 44.6 ± 3.2 and 83.8 ± 2.1, respectively. The mean knee function section of the KSS was measured at 98.2 ± 7.2. The mean KOOS score and the mean knee ROM were 84 ± 9.4 and 134.4 ± 7º, respectively. The mean VAS for pain was 8.9 ± 1.1 (range 8-10) before the operation and 1.2 ± 0.8 (range 0-2) at the last follow-up. All the patients were very satisfied (n=14) or satisfied (n=3) with the results. No postoperative complication or reoperation was recorded during the follow-up. Unicompartmental knee arthroplasty provides satisfactory outcomes and a high survival rate, at least in mid-term follow-up. These findings suggest increased use of UKA in future workups.

Impact of Nordic Arthroplasty Register Association (NARA) collaboration on demographics, methods and revision rates in knee arthroplasty: a register-based study from NARA 2000-2017.

We have previously observed differences in treatment and outcome of knee arthroplasties in the Nordic countries. To evaluate the impact of Nordic collaboration in the last 15 years we aimed to compare patient demographics, methods, and revision rates in primary knee arthroplasties among the 4 Nordic countries. We included 535,051 primary knee arthroplasties reported 2000-2017 from the Nordic Arthroplasty Register Association (NARA) database. Kaplan-Meier analysis (KM) and restricted mean survival time (RMST) analysis were used to evaluate the cumulative revision rate (CRR) and RMST estimates with 95% confidence intervals (CI) and to compare countries in relation to risk of revision for any reason. After 2010, the increase in incidence of knee arthroplasty plateaued in Sweden and Denmark but continued to increase in Finland and Norway. In 2017 the incidence was highest in Finland with 226 per 105 person-years, while it was less than 150 per 105 in the 3 other Nordic countries. In total knee arthroplasties performed for osteoarthritis (OA), overall CRR at 15 years for revision due to any reason was higher in Denmark (CRR 9.6%, 95% CI 9.2-10), Norway (CRR 9.1%, CI 8.7-9.5), and Finland (CRR 7.0%, CI 6.8-7.3) compared with Sweden (CRR 6.6%, CI 6.4-6.8). There were differences among the countries in use of implant brand and type, fixation, patellar component, and use of unicompartmental knee arthroplasty. We evinced a slowing growth of incidence of knee arthroplasties in the Nordic countries after 2010 with Finland having the highest incidence. We also noted substantial differences among the 4 Nordic countries, with Sweden having a lower risk of revision than the other countries. No impact of NARA could be demonstrated and CRR did not improve over time.

Incidence, temporal trends and potential risk factors for aseptic loosening following primary unicompartmental knee arthroplasty: A meta-analysis of 96,294 knees

BackgroundAseptic loosening (AL) is among the major reasons for revision of failed primary unicompartmental knee arthroplasty (UKA). There is an ongoing temporal increase in the use of UKA with a resultant increase in the revision burden. We aimed to evaluate the incidence of, temporal trends and risk factors for AL. MethodsLongitudinal studies reporting the incidence of AL following primary UKA were sought from MEDLINE, Embase, Web of Science and Cochrane Library up to 6th April 2020. Incidence and relative risks (RR) (with 95% confidence intervals) were calculated. ResultsWe identified 62 studies for inclusion. Overall, 96,294 primary UKA procedures accounting for 1752 AL cases were included. AL incidence ranged from 0.00% to 22.70% over a 7.7 year weighted mean follow-up. The pooled random effects incidence (95% CI) was 1.77% (1.34–2.25) in the same follow-up period. The annual rate of AL was 0.10% (0.02–0.22). AL incidence increased with length of follow-up, but there was a temporal decrease from the 1970s onwards. Tibial loosening was more common than femoral component loosening: incidence (95% CI) of 1.63% (0.96–2.44) and 0.58% (0.20–1.09) respectively over a weighted follow-up of 6.6 years. Fixed bearing implant design and cemented fixation were both associated with increased AL risk, whereas robotic-assisted surgery was associated with decreased risk. ConclusionThe overall incidence of AL following primary UKA is primarily driven by tibial component loosening and there is a temporal decline in rates. The use of mobile bearing, uncemented implants inserted with robotic assisted surgery may reduce the risk of AL.

Robotic-assisted vs conventional surgery in medial unicompartmental knee arthroplasty: a clinical and radiological study

BackgroundThe use of unicompartmental knee arthroplasty (UKA) has increased and new technologies have been developed to improve patient survival and satisfaction, soft tissue balance, alignment, and component size. Robot-assisted systems offer an increase in surgical precision and accuracy. The purpose of this study is to evaluate the precision of component position using five radiological parameters in conventional and robotic-assisted medial UKA using the NAVIO system.MethodsA cohort study was designed for patients who underwent medial UKA between April 2017 and March 2019 in a single center. Patients were allocated in the conventional (UKA-C) or robotic-assisted (UKA-R) group. The variables analyzed were age, gender, affected knee side, length of hospital stay, surgical time, and radiological measurements such as anatomical medial distal femoral angle (aMDFA), anatomical medial proximal tibial angle (aMPTA), tibial slope, the sagittal femoral angle, and the component size. A target was defined for each measurement, and a successful UKA was defined if at least four radiological measures were on target after surgery. Also, patients’ reported outcomes were evaluated using the Oxford Knee Score (OKS) and a numeric rating scale (NRS) for pain.ResultsThirty-four patients were included, 18 of them underwent UKA-R. The success rate for UKA in the UKA-R group was 87%; meanwhile, in the UKA-C group this was 28%, this difference was significant and powered (Fisher’s exact test, p = 0.001; 1 − β = 0.95). Also, a 5-point difference in favor of the UKA-R group in the median OKS (p = 0.01), and a significantly lower median NRS for pain (p < 0.000) were found after surgery.ConclusionsUKA-R achieved more precision in the radiological parameters’ measure in this study. Also, UKA-R has a trend towards a better OKS and a lower NRS for pain at short-term follow-up.

Similar revision rates in clinical studies and arthroplasty registers and no bias for developer publications in unicompartmental knee arthroplasty

PurposeOur aim was to assess the outcome with respect to cumulative revision rates of unicompartmental knee arthroplasty (UKA) by comparing published literature and arthroplasty registry data. Our hypothesis was that there is a superior outcome of UKA described in dependent clinical studies compared to independent studies or arthroplasty registers.MethodsA systematic review of all clinical studies on UKA in the past decade was conducted with the main endpoint revision rate. Revision rate was calculated as “revision per 100 component years (CY)”. The respective data were analysed with regard to a potential difference of the percentage of performed revision surgeries as described in dependent and independent clinical studies. Clinical data were further compared to arthroplasty registers in a systematic search algorithm.ResultsIn total, 48 study cohorts fulfilled our inclusion criteria and revealed 1.11 revisions per 100 CY. This corresponds to a revision rate of 11.1% after 10 years. No deviations with regard to revision rates for UKA among dependent and independent clinical literature were detected. Data from four arthroplasty registers showed lower survival rates after 10 years compared to published literature without being significant.ConclusionsThe outcomes of UKA in dependent and independent clinical studies do not differ significantly and are in line with arthroplasty register datasets. We cannot confirm biased results and the authors recommend the use of UKAs in properly selected patients by experts in their field.

Medial unicompartmental knee arthroplasty: increasingly uniform patient demographics despite differences in surgical volume and usage—a descriptive study of 8,501 cases from the Danish Knee Arthroplasty Registry

Background and purpose — Using contemporary indications, up to 50% of patients undergoing knee arthroplasty are eligible for unicompartmental knee arthroplasty (UKA), and lower UKA use likely reflects a restrictive approach to patient selection. Since broader indications have been successfully introduced, and low surgical volume and UKA percentage (usage) are associated with higher revision rates, it is of interest whether the actual use of UKA has changed accordingly. We explored this by assessing time trends in patient demographics and whether these are associated with center UKA volume and usage.Patients and methods — From the Danish Knee Arthroplasty Registry, we included 8,501 medial UKAs performed for primary osteoarthritis during 2002–2016. Using locally weighted regression, we examined changes—both overall and by center volume and usage (low vs high)—in sex distribution, age, weight, and preoperative American Knee Society Score (AKSS-O).Results — Over the last 20 years, UKA use in Denmark has been increasing steadily. Age, weight, and proportion of men all increased regardless of volume and usage. AKSS-O showed an initial increase followed by a decrease. In low-usage and low-volume centers, the proportion of women was higher, patients were younger, weighed less, and had higher AKSS-O scores; however, for age and AKSS-O, the groups were converging during the last part of the period.Interpretation — Characteristics of UKA patients have changed in the last 15 years irrespective of center volume and usage. We found between-group differences for both volume and usage, though with convergence for age and AKSS-O, which suggests an increasingly uniform approach to patient selection.

Unicompartmental knee arthroplasty

This review on the use of unicompartmental knee arthroplasty (UKA) examines the history of UKA development, considers indications and compares fixed and mobile bearing designs. Advantages of the use of UKA in anteromedial knee osteoarthritis compared to the use of TKA are addressed, followed by a formal review of the literature concerning survival analyses in both designer and non-designer series as well as registry data. The expanding role and future for partial knee arthroplasty is discussed.

Ten- to 15-year results of the Oxford PhaseIII mobile unicompartmental knee arthroplasty: a prospective study from a non-designer group.

AimsThe interest in unicompartmental knee arthroplasty (UKA) for medial osteoarthritis has increased rapidly but the long-term follow-up of the Oxford UKAs has yet to be analysed in non-designer centres. We have examined our ten- to 15-year clinical and radiological follow-up data for the Oxford Phase III UKAs.Patients and MethodsBetween January 1999 and January 2005 a total of 138 consecutive Oxford Phase III arthroplasties were performed by a single surgeon in 129 patients for medial compartment osteoarthritis (71 right and 67 left knees, mean age 72.0 years (47 to 91), mean body mass index 28.2 (20.7 to 52.2)). Both clinical data and radiographs were prospectively recorded and obtained at intervals. Of the 129 patients, 32 patients (32 knees) died, ten patients (12 knees) were not able to take part in the final clinical and radiological assessment due to physical and mental conditions, but via telephone interview it was confirmed that none of these ten patients (12 knees) had a revision of the knee arthroplasty. One patient (two knees) was lost to follow-up.ResultsThe mean follow-up was 11.7 years (10 to 15). A total of 11 knees (8%) were revised. The survival at 15 years with revision for any reason as the endpoint was 90.6% (95% confidence interval (CI) 85.2 to 96.0) and revision related to the prosthesis was 99.3% (95% CI 97.9 to 100). The mean total Knee Society Score was 47 (0 to 80) pre-operatively and 81 (30 to 100) at latest follow-up. The mean Oxford Knee Score was 19 (12 to 40) pre-operatively and 42 (28 to 55) at final follow-up. Radiolucency beneath the tibial component occurred in 22 of 81 prostheses (27.2%) without evidence of loosening.ConclusionThis study supports the use of UKA in medial compartment osteoarthritis with excellent long-term functional and radiological outcomes with an excellent 15-year survival rate.Cite this article: Bone Joint J 2016;98-B(10 Suppl B):41–7.

Indications, outcomes, and complications of unicompartmental knee arthroplasty.

Improved prosthetic design and application of strict criteria in selection of patients have resulted in wide use of unicompartmental knee arthroplasty (UKA) in surgical treatment of damaged joints. Here, we review the contemporary indications, outcomes, and complications of procedures such as lateral and medial UKA and total knee arthroplasty (TKA), and compare the severity of these complications in UKA and TKA. Patients who received unicompartmental femorotibial osteoarthritis and patients who underwent UKA and ACL reconstruction for deficiency in anterior cruciate ligament (ACL), they all showed good clinical outcomes and survival. Reliable and successful options in the treatment of patients with isolated tibiofemoral osteoarthritis include lateral and medial UKA.

Unicompartmental Knee Arthroplasty and Total Knee Arthroplasty Among Medicare Beneficiaries, 2000 to 2009

Unicompartmental knee arthroplasty is a less-invasive alternative to total knee arthroplasty for patients with arthritis affecting only the medial or lateral compartment. However, little is known about recent trends in the use of these procedures and the associated outcomes among older patients. With use of a nationally representative 5% sample of Medicare beneficiaries who were sixty-five years of age or older and who had undergone either unilateral unicompartmental knee arthroplasty or unilateral total knee arthroplasty from 2000 to 2009, we assessed trends in the use of unicompartmental and total knee arthroplasty, associated durations of hospital stay, and postoperative outcomes. The outcome measures were the rates of implant revision or removal within five years and the rates of periprosthetic infection, thromboembolic events, myocardial infarction, and all-cause mortality within one year. We conducted Kaplan-Meier analyses to assess the cumulative incidence of unadjusted outcomes and used Cox proportional-hazards regression to understand the relative risks of the outcomes for each procedure. A total of 68,603 patients underwent unilateral total knee arthroplasty (n = 65,505) or unilateral unicompartmental knee arthroplasty (n = 3098) from 2000 to 2009. The mean age was seventy-five years; 34% of the patients were men, and 92% were white. The procedure rate was twenty-one times higher for total knee arthroplasty (597 per 100,000 person-years) than unicompartmental knee arthroplasty (twenty-nine per 100,000 person-years). The use of total knee arthroplasty increased 1.7-fold, and the use of unicompartmental knee arthroplasty increased 6.2-fold. The mean length of stay (and standard deviation [SD]) was 3.9 ± 2.1 days for total knee arthroplasty and 2.4 ± 1.7 days for unicompartmental knee arthroplasty. The five-year revision rate was 3.7% for total knee arthroplasty and 8.0% for unicompartmental knee arthroplasty. After multivariable adjustment, the risk of revision remained 2.4 times higher for unicompartmental knee arthroplasty than for total knee arthroplasty (95% confidence interval [CI] = 2.03 to 2.83). After multivariable adjustment, patients who underwent unicompartmental knee arthroplasty had no significant differential one-year risk of infection (adjusted hazard ratio [HR] = 0.74; 95% CI = 0.55 to 1.01), thromboembolic events (adjusted HR =0.86; 95% CI = 0.57 to 1.29), or mortality (adjusted HR = 0.75; 95% CI = 0.50 to 1.11). Although unicompartmental knee arthroplasty accounted for only 4.5% of the unilateral knee replacements among Medicare beneficiaries, the use of this procedure has increased dramatically. Compared with those who had total knee arthroplasty, patients who underwent unicompartmental knee arthroplasty had higher revision rates but shorter durations of stay and tended to have lower rates of perioperative complications. These findings need to be confirmed by studies that incorporate detailed clinical information.

Management of osteoarthritis of the knee

Total knee arthroplasty (TKA) is a successful operation. Knee osteoarthritis is an increasing healthcare burden and the number of arthroplasty procedures implanted each year is estimated to increase exponentially over the next 10 years. At present in the UK, over 90% of these procedures are performed as total knee replacements mirroring similar findings in other countries.1 Over the last 10 years, there has been increased interest in partial knee replacement as an alternative treatment option for knee osteoarthritis. Although each of the three compartments of the knee can be treated with partial replacement, the commonest form of partial replacement involves the medial side of the joint (Fig. 1). The indications for medial unicompartmental knee arthroplasty (UKA) have been defined more clearly and many patients who undergo TKA do meet the criteria for a UKA procedure. This article will outline the argument for increased use of UKA on the medial side of the knee in place of total knee replacement. Figure 1 (A) An anteroposterior radiograph of a knee demonstrating anteromedial osteoarthritis. This pattern of disease is the commonest indication for UKA (B). In building the case for the use of unicompartmental knee replacement, four important areas should be considered: (i) the immediate patient benefits; (ii) the long-term clinical outcome of UKA implants; (iii) the number of patients who are eligible for the procedure; and (iv) the health economics of UKA use.

Minimum Five Years Follow-up of Unicompartmental Knee Arthroplasty in Patients Age 60 or Younger

Unicompartmental osteoarthrosis of the knee is a challenging and controversial problem in the middle-aged patient. An ideal solution for younger patients would be durable and bone sparing. The purpose of this paper is to report the early clinical and radiographic results with use of unicompartmental knee arthroplasty (UKA) in patients 60 years of age or younger.

Analysis of 13 early failures of the mobile bearing Oxford phase III unicompartmental knee prosthesis

The use of unicompartmental knee arthroplasty appears to be increasing despite a significant number of early revisions. This study looks at a consecutive series of such procedures. We retrospectively reviewed thirteen patients who had a revision of a unicompartmental knee replacement between January 2003 and March 2008 inclusively. During the study period, a total of 141 UKAs were performed in the reporting unit, of those 9 were revised to TKA. The indication for revision to TKA was determined from clinical records and radiographs. All patients who underwent revision were followed up using Oxford Knee Score. No preoperative Oxford Knee Scores were available. The study group consisted of six men and seven women. The preoperative diagnosis was osteoarthritis in all cases. The mean follow-up time was 16.4 ± 10.7 months (range: 2–36 months). The mean age of the patients at time of revision was 60.8 ± 9.7 years (range: 50–77 years). All patients had undergone medial UKA. The mean time interval between primary surgery and revision surgery was 21.5 ± 13.4 months (range: 5–48 months). The indications for revision included loosening of the tibial and/or femoral component (n = 7), progression of osteoarthritis to lateral compartment (n = 2), unexplained medial knee pain (n = 2) patellofemoral symptoms (n = 1), and insert dislocation (n = 1). The mean postoperative Oxford Knee Score at the latest follow-up evaluation was 14 ± 6.5 (range: 5–26). For the majority of patients, UKA provides reliable and reproducible results. However, UKA is a demanding procedure that needs special experience and includes a risk of early failure.

Outcomes of Total and Unicompartmental Knee Arthroplasty for Secondary and Spontaneous Osteonecrosis of the Knee

The reported outcomes of patients who underwent total or unicompartmental knee arthroplasty for secondary and spontaneous osteonecrosis of the knee are often from studies that lack the number of subjects necessary to generate meaningful conclusions. We systematically reviewed the available literature in order to define the outcomes of patients after total knee arthroplasty for secondary osteonecrosis and after total or unicompartmental knee arthroplasty for spontaneous osteonecrosis of the knee. A literature review yielded twenty cohorts with demographic patient information and outcome scores (global knee scores, radiographic outcomes, and revision rates) for patients who had knee arthroplasty as treatment for either secondary or spontaneous osteonecrosis of the knee. The mean preoperative and postoperative global knee scores, the mean revision rate, and the categorization of the mean "poor" and mean "good" outcomes for the knees with each underlying disease were tabulated and reported. The demographic data and the reported mean global knee scores were weighted by the number of knees in each study. Total knee arthroplasty was performed in 150 knees with secondary osteonecrosis and 148 knees with spontaneous osteonecrosis, and unicompartmental knee arthroplasty was performed in sixty-four knees with spontaneous osteonecrosis. Total knee arthroplasty for spontaneous osteonecrosis of the knee was associated with the best outcomes (higher "good" and postoperative global knee scores and lower revision [3%] and "poor" outcome [6%] rates compared with the other two groups). The outcomes after total knee arthroplasty in knees with secondary osteonecrosis as well as in knees with spontaneous osteonecrosis were better in the cohorts operated on during or after 1985 than in those operated on before 1985. Similarly, the outcomes after unicompartmental knee arthroplasty in knees with spontaneous osteonecrosis of the knee were also better in the cohorts operated on during or after 1985 than in those operated on before 1985. Total knee arthroplasty performed as treatment for either secondary osteonecrosis or spontaneous osteonecrosis and unicompartmental knee arthroplasty performed as treatment for spontaneous osteonecrosis were associated with improved outcomes in cohorts with more recent operative dates. The evidence suggests that the use of contemporary cemented implants in total knee arthroplasty and the selective use of stems and augments in patients who have development of secondary osteonecrosis after total knee arthroplasty are producing outcomes that are comparable to those seen after total knee arthroplasty for osteoarthritis. Although the outcomes of patients who have total knee arthroplasty for the treatment of spontaneous osteonecrosis of the knee have historically been favorable, such outcomes have also shown particular improvement in the studies from more recent operative periods. Although poor outcomes were seen after unicompartmental knee arthroplasty in earlier studies of patients with spontaneous osteonecrosis of the knee, it is possible that those results were secondary to inappropriate patient selection, as the authors of the most recent and, to our knowledge, the only study to follow established operative indications regarding the use of unicompartmental knee arthroplasty reported excellent results. Therapeutic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.