Knee joint laxity and passive stiffness in meniscectomized patients compared with healthy controls

Background: Passive mechanical behavior of the knee in the frontal plane, measured as angular laxity and mechanical stiffness, may play an important role in the pathogenesis of knee osteoarthritis (OA). Little is known about knee laxity and stiffness prior to knee OA onset. We investigated knee joint angular laxity and passive stiffness in meniscectomized patients at high risk of knee OA compared with healthy controls. Methods: Sixty patients meniscectomized for a medial meniscal tear (52 men, 41.4 ± 5.5 years, 175.3 ± 7.9 cm, 83.6 ± 12.8 kg, mean ± SD) and 21 healthy controls (18 men, 42.0 ± 6.7 years, 176.8 ± 5.7 cm, 77.8 ± 13.4 kg) had their knee joint angular laxity and passive stiffness assessed twice ~ 2.3 years apart. Linear regression models including age, sex, height and body mass as covariates in the adjusted model were used to assess differences between groups. Results: Greater knee joint varus (− 10.1 vs. − 7.3°, p < 0.001), valgus (7.1 vs. 5.6°, p = 0.001) and total (17.2 vs. 12.9°, p < 0.001) angular laxity together with reduced midrange passive stiffness (1.71 vs. 2.36 Nm/°, p < 0.001) were observed in patients vs. healthy controls. No differences were observed in change in stiffness over time between patients and controls, however a tendency towards increased laxity in patients was seen. Conclusions: Meniscectomized patients showed increased knee joint angular laxity and reduced passive stiffness ~ 3 months post surgery compared with controls. In addition, the results indicated that knee joint laxity may increase over time in meniscectomized patients