Summary
In Asian patients with severe lateral OA (K-L grade 3 or 4), a substantial proportion had varus or neutral knee alignment. Nonvalgus patients with bone-on-bone lateral OA (K-L grade 4) presented with a significantly milder clinical manifestation.
Abstract
Background
The relationship between lateral osteoarthritis (OA) and valgus knee alignment has been studied extensively. However, little research is available on lateral OA with nonvalgus (i.e. neutral or varus) knee alignment.
QUESTIONS / PURPOSES
(1) We attempted to identify the proportion of nonvalgus knee alignment in Asian patients diagnosed with severe lateral OA (Kellgren-Lawrence [K-L] grade 3 or 4)
(2) We attempted to demonstrate that nonvalgus bone-on-bone lateral OA (K-L grade 4) patients presented with a milder clinical manifestation than valgus bone-on-bone lateral OA.
Methods
We retrospectively reviewed the records of 825 knees in 647 patients who visited our outpatient clinic and were diagnosed with lateral OA between September 2008 and March 2018. Knee OA was evaluated according to the K-L grading system. Lateral OA patients with K-L grade 3 or 4 were enrolled in this study. Alignment was measured by the hip–knee–ankle (HKA) angle on full-limb radiographs, and was classified as varus (<180°), neutral (180°) or valgus (>180°).
We divided the patients with K-L grade 4 lateral OA into two groups according to their knee alignment (nonvalgus and valgus) and reviewed the recommended treatment (surgery or conservative treatment). The ?2 test was used to analyse the difference in distribution of the recommended treatment between the two groups.
Results
Of the 825 knees, 272 (32.9%) were K-L grade 1 or 2, and 553 (67.1%) were K-L grade 3 or 4. Of the latter 553 knees, 113 (20.4%) had neutral, 129 (23.3%) varus, and 311 (56.2%) valgus alignment. Notably, 44% of these 553 knees had nonvalgus alignment. (95% confidence interval, 40%–48%, exact binomial test).
When the K-L grade 4 patient group (bone-on-bone arthritis, 263 knees) was divided into nonvalgus and valgus groups, the proportion of patients recommended for conservative treatment was significantly higher in the nonvalgus than in the valgus group. (?2 test, P = 0.003). Sex, age and body mass index were not significantly different between the two groups.
Conclusions
In Asian patients with severe lateral OA (K-L grade 3 or 4), a substantial proportion had varus or neutral knee alignment. Nonvalgus patients with bone-on-bone lateral OA (K-L grade 4) presented with a significantly milder clinical manifestation.