Valgus Arthritic Knee Responds Better to Conservative Treatment than the Varus Arthritic Knee

Abstract

Background and Objectives: Clinically, it is beneficial to determine the knee osteoarthritis (OA) subtype that responds well to conservative treatments. Therefore, this study aimed to determine the differences between varus and valgus arthritic knees in the response to conservative treatment. We hypothesized that valgus arthritic knees would respond better to conservative treatment than varus arthritic knees. Materials and Methods: Medical records of 834 patients who received knee OA treatment were retrospectively reviewed. Patients with Kellgren-Lawrence grades III and IV were divided into two groups according to knee alignment (varus arthritic knee, hip-knee-ankle angle [HKA] > 0° or valgus arthritic knee, HKA < 0°). The Kaplan-Meier curve with total knee arthroplasty (TKA) as an endpoint was used to compare the survival probability between varus and valgus arthritic knees at one, two, three, four, and five years after the first visit. A receiver operating characteristic (ROC) curve was used to compare the HKA thresholds for TKA between varus and valgus arthritic knees. Results: Valgus arthritic knees responded better to conservative treatment than varus arthritic knees. With TKA as an endpoint, the survival probabilities for varus and valgus arthritic knees were 24.2% and 61.4%, respectively, at the 5-year follow-up (p < 0.001). The thresholds of HKA for varus and valgus arthritic knees for TKA were 4.9° and -8.1°, respectively (varus: area under the ROC curve [AUC] = 0.704, 95% confidence interval [CI] 0.666-0.741, p < 0.001, sensitivity = 0.870, specificity = 0.524; valgus: AUC = 0.753, 95% CI 0.693-0.807, p < 0.001, sensitivity = 0.753, specificity = 0.786). Conclusions: Conservative treatment is more effective for valgus than for varus arthritic knees. This should be considered when explaining the prognosis of conservative treatment for knees with varus and valgus arthritis.

Keywords: Kaplan–Meier curve; conservative treatment; hip-knee-ankle angle; osteoarthritis; receiver operating characteristic curve; total knee arthroplasty; valgus alignment; valgus arthritic knee; varus alignment; varus arthritic knee.

Figure 1

Flow diagram illustrating patient enrollment. n, number; KL, Kellgren–Lawrence; NRS, numeric rating scale; TKA, total knee arthroplasty.

Figure 2

Diagrammatic representation of the treatment protocol. The effect was evaluated using a NRS. If the NRS remained >4 after 2–3 weeks, the next step was performed. (NRS: Higher scores indicate more pain.) * Switching a specific drug was based on previous exposure to specific NSAIDs and SYSADOAs. NRS, numeric rating scale; NSAID, non-steroidal anti-inflammatory drug; SYSADOA, slow-acting drug for osteoarthritis; AAP, acetaminophen; TKA, total knee arthroplasty.

Figure 3

Five-year Kaplan–Meier survivorship curve for varus and valgus arthritic knees.

Figure 4

One-year Kaplan–Meier survivorship curve for varus and valgus arthritic knees.

Figure 5

ROC curve for TKA of varus and valgus arthritic knees using the HKA. ROC, receiver operating characteristic; TKA, total knee arthroplasty; AUC, area under the ROC curve; HKA, hip–knee–ankle angle.