Abstract
Objectives To investigate the relationship between external knee adduction moment (KAM) and knee osteoarthritis (OA) symptoms according to static alignment and pelvic drop. Methods Ninety-five participants with symptomatic knee OA were included. Radiographic severity was graded by Kellgren and Lawrence (KL) scale. The hip-knee-ankle (HKA) angle was used to assess limb alignment from a full-length lower-limb radiograph. KAM-related variables (peak KAM and KAM impulse) and pelvic drop angle were determined from 3D gait analysis. Symptoms were assessed via visual analog scale (VAS) for pain and hospital for special surgery (HSS) score for physical function. The relationship between KAM and symptoms was evaluated according to radiographic severity and pelvic drop using linear models. Results According to the more affected knee in the varus group, both the two KAM-related measures (peak KAM and KAM impulse) were positively associated with greater VAS pain and were negatively associated with HSS score. Only peak KAM was correlated with VAS and HSS in the valgus group. VAS pain score of the more affected knee was positively correlated with pelvic drop angle. Stratified by pelvic drop angle, KAM-related variables were more positively associated with VAS pain and negatively associated with HSS score for patients with pelvic drop angle ≤3 degrees. The relationships between KAM and symptoms according to radiographic disease severity remained confusing. Conclusions Static alignment and pelvic drop angle significantly affected relationships between KAM-related variables and knee OA symptoms, which may explain the confusing results as shown by previous studies.
Highlights
Knee osteoarthritis (OA) is a major cause of pain and physical disability [1]. e external knee adduction moment (KAM), which reflects medial-to-lateral knee joint load distribution during gait, has become an OA treatment target [2,3,4]. e KAM is a strong predictor of presence [5], severity [6,7,8], and the rate of progression [9] of knee OA [10]
Failure to consider the determinative factors of KAM may account for the inconsistent findings from existing studies
visual analog scale (VAS) pain score of the more affected knee was positively associated with pelvic drop angle (r 0.256, regression coefficient 0.585, P 0.025) (Figure 1)
Summary
Knee osteoarthritis (OA) is a major cause of pain and physical disability [1]. e external knee adduction moment (KAM), which reflects medial-to-lateral knee joint load distribution during gait, has become an OA treatment target [2,3,4]. e KAM (peak and impulse) is a strong predictor of presence [5], severity [6,7,8], and the rate of progression [9] of knee OA [10]. Despite the use of the KAM as a biomechanical treatment target, the relationships between KAM-related variables and knee OA symptoms (pain and function) remain unclear [12]. Several studies showed positive correlations between the KAM and knee pain [13,14,15,16], while other investigations demonstrated inverse associations [17]. With respect to relationships between KAM and knee joint function, evidences were conflicting [14, 15, 17]. Recent studies considered that relationships between KAM-related variables and symptoms may differ according to underlying structural knee OA severity, and tried to explain the inconsistent findings of studies to date [10, 12]. Henriksen et al reported that patients with severity of knee OA ≤ KL grade 2 showed negative relationships between KAM and pain, while those with severity of knee OA > KL grade 2 showed a positive relationship between pain and BioMed Research International
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