M. van der Esch, PT, M.P.M. Steultjens, PhD, Prof. J. Dekker, PhD

The aim of the study is to answer the following research questions: 1) Is there a relationship between knee joint stability and structural joint damage in patients with osteoarthritis of the knee? 2) Is there a relationship between the stability of the knee joint and the level of functional disability in patients with osteoarthritis of the knee?

In this cross-sectional study, 86 patients with osteoarthritis of the knee were investigated. Measurements were made to establish the laxity (passive stability) of the knee joint. Laxity was expressed as the range of motion of the tibiofemoral joint in the frontal plane, when applying a medial or lateral load of 8Nm. Additionally, the degree of structural damage (joint space narrowing and osteophyte formation) in the knee joints using radiographs was assessed. Using the WOMAc questionnaire and a 5x10m walking test, data were collected on the level of physical functioning of patients. Isokinetic muscle strength for flexion and extension of the knee were measured at 60°/s using an EN-Knee chair.

Laxity of the knee joint was found to be related to the degree of structural damage in the knee (research question #1). Knees with a high level of joint space narrowing were on average more lax than knees with less joint space narrowing. However, no relationship was found between laxity and presence of osteophytes. A weak direct relationship was found between knee joint laxity and walking speed (research question #2). Patients with highly lax joints tended to walk slower than patients with less lax joints. The correlation was statistically significant but low. No significant correlation was found between the WOMAC scores and knee joint laxity. However, it was found that the relationship between muscle strength and physical functioning (which is normally quite strong) was absent in patients with highly lax knees.