Combined anterior and rotational laxity measurements allow characterizing personal knee laxity profiles in healthy individuals

Abstract

PurposeThe aim of this study was to quantify sagittal and rotational knee laxity profiles taking into account individual influencing factors.MethodsLinear regression models were used to determine which individual characteristics (age, height, body mass and sex) influenced the outcome in a group of 104 healthy subjects. The standardized residuals were used as individualized (corrected) laxity scores and were combined to determine knee laxity profiles. ResultsAnterior knee laxity was not influenced by individual characteristics. Rotational knee laxity was higher in females and inversely related to body mass. The correlation between anterior laxity and internal rotation scores was weak (r = 0.24, p = 0.02). The proportion of knees concerned by increased laxity scores (scores >1) was similar for anterior displacement, internal and external rotation (15 %). Only 32 % of the tested subjects showed a normal profile (score >−1 and <1) for all three directions, 33 % were concerned by hyperlaxity, 40 % by hypolaxity and 5 % by both. ConclusionsThe diversity of laxity profiles found here highlights that the interpretation of multidirectional knee laxity is complex and suggests the necessity for individualized care of knee diseases and injuries. These results contribute to the understanding of knee laxity and throw the basis for prevention strategies and improvement of treatment outcomes in injuries and diseases.Level of evidenceCase series with no comparison groups, Level IV.

Objective measurements of static anterior and rotational knee laxity

“…As for rotational knee laxity, it has been shown that women have up to 40 % higher knee rotation compared to men [32]. This difference has been confirmed by several investigations [18,32,36,55]. It may represent one of the factors explaining the higher risk for ACL injuries in females.…”

“…Regarding the second version of the Rotameter, it yields lower values for rotational laxity than the first device due to improvements in the standardization of the patient installation and joint fixation. The Minimum Detectable Change (MDC) has been determined to reach 4.2°for internal rotation and 5.9°for external rotation [18]. Individualized normative references have been established taking into account gender and body mass [18,35].…”

“…The Minimum Detectable Change (MDC) has been determined to reach 4.2°for internal rotation and 5.9°for external rotation [18]. Individualized normative references have been established taking into account gender and body mass [18,35]. -Robotic Knee Testing system [36]: The patient lies supine with knees flexed at 25°.…”

“…It may represent one of the factors explaining the higher risk for ACL injuries in females. Body mass also influences rotational laxity with increased body mass being related to lower knee rotation [18,56].…”

“…Vauhnik et al reported a low precision of the device with measurement errors up to 3.8 mm [17]. However, much lower measurements errors of 1.2 mm have recently been reported [18] in a study that insisted strongly on the standardization of patient positioning and testing protocol. -RadioStereometry Analysis (RSA) [19]: This method requires the surgical implantation of intra osseous tantalum beads of a diameter of 0.8 to 1.6 mm [19].…”