An investigation into the effects of a simulated effusion in healthy subjects on knee kinematics during jogging and running

Abstract

Background

Knee joint effusion can lead to changes in the activation of surrounding musculature and result in delayed return to baseline daily and sporting activity following injury. However, the effects of an isolated knee joint effusion on control of movement during cyclical activities such as gait are poorly understood.

Methods

Knee angular displacement and velocity was measured during treadmill jogging (8 km h⁻¹) and running (12 km h⁻¹) in 12 healthy subjects before and after a simulated knee joint effusion. Two separate pre-effusion recordings were taken to account for test–retest variability in gait measurement techniques.

Findings

Subjects demonstrated a small yet significant decrease in peak knee flexion following heel strike at 8 km h⁻¹ as a result of the effusion (P < 0.05). However, there were no significant effects seen at 12 km h⁻¹.

Interpretation

Previous work has suggested that knee joint movement during walking and jump landing is affected by an effusion. However, this work demonstrates that these effects are minimal during jogging and running. Our results suggest that it may be prudent to consider measurement variability in future studies of this nature.

Introduction

Knee joint injuries are commonly associated with activities that demand high levels of stability during dynamic movement. Depending on the mechanism and type of injury, a resultant effusion distends the knee joint capsule resulting in arthrogenic muscle inhibition which may lead to weakness and atrophy in the surrounding musculature (Palmieri et al., 2005). Arthrogenic muscle inhibition is defined as an ongoing reflex inhibition of the musculature surrounding a joint following distension or damage to the structures of that joint (Hopkins and Ingersoll, 2000).

Neuromuscular control at the knee joint is imperative in order to provide stability which allows us to complete everyday activities such as walking, running and jumping. A lack of sufficient control and strength at the knee as a result of arthrogenic muscle inhibition can lead to the development of chronic degenerative conditions (Suter and Herzog, 2000, Lewek et al., 2002), as well as predisposing patients to reinjury (Stokes and Young, 1984). The stimulation of mechanoreceptors located in skin, ligaments, muscles and joints, provides afferent feedback via spinal pathways regarding joint movement and position in various body segments during gait. Interneurons are key components in the spinal circuitry and they function to transmit excitatory and inhibitory signals to other interneurons as well as to alpha and gamma motoneurons (Palmieri et al., 2005). The presence of a knee effusion may affect these signals by altering the alpha motoneuron discharge to motor pathways, resulting in arthrogenic muscle inhibition and subsequent changes in normal movement patterns. However, studies that have evaluated movement characteristics of subjects with knee effusion in their post-injury or pathological state cannot establish whether a change in movement patterns is a direct result of knee pathology or contributed to its etiology.

The majority of the research to date on the effects of knee effusion has used a simulated effusion model to evaluate knee function of healthy subjects in static, non-functional positions. These studies have investigated quadriceps H-reflex (Hopkins et al., 2000, Palmieri et al., 2003a, Palmieri et al., 2003b, Palmieri et al., 2005), muscle strength measures (McNair et al., 1996), proprioception (Barrack et al., 1983, McNair et al., 1995) and postural control (Palmieri et al., 2003a, Palmieri et al., 2003b, Oksendahl et al., 2007). All of these studies have provided important information regarding the effect of effusions on static measures but are not reflective of gross functional motor tasks which require feedback regarding movement and position during multiple joint movement such as gait. A small number of researchers have investigated lower limb movement patterns during functional activity in healthy subjects following a simulated effusion. Palmieri-Smith et al. (2007) investigated the effects of an effusion on movement patterns and electromyographic (EMG) activity during a drop landing in healthy subjects. They observed a more extended knee position upon landing and a reduced knee extension moment and quadriceps EMG activity post-impact compared to baseline and the injection of lidocaine. The authors hypothesised that a reduction in EMG activity, and therefore weakened quadriceps following an effusion, altered landing mechanics causing a greater amount of knee extension and therefore large forces to be transferred through the knee. Marshall et al. (1993) observed two distinctly different patterns of change in ankle joint movement during walking following effusions of 30, 60 and 90 ml in the knee joint yet no consistent group effect. No kinematic changes were found at the hip and knee joints. However, Torry et al. (2000) found that a knee effusion of 50 and 80 ml resulted in small yet significantly increased flexion at heel strike and greater average flexion throughout the stance phase at both the hip and the knee during walking. Another recent study by Torry et al. (2005) investigated the effects of a 20 ml effusion at the knee and demonstrated no change in the average knee angle during the stance phase of jogging despite a reduction in quadriceps EMG activity in the majority of their subjects. The lack of a consistent pattern in the results of studies suggests that further work is required to understand how the neuromuscular system responds to the presence of an effusion in functional activities further investigation is needed.

A possible explanation for the lack of consistent results from these studies may be due to potential test–retest measurement errors associated with kinematic studies (Monaghan et al., 2007) and the fact that multiple functional activities have not been examined in the same subject group in a single study. In assessing the effect of an effusion, observed differences in joint movement must be greater than test–retest variance for an effect to be true. The aims of the present study were to address potential measurement error by performing a kinematic analysis on healthy subjects on three occasions – twice prior to and once post a knee joint effusion. Furthermore, in an effort to establish the consistency of effect at different running velocities we have analysed knee movement during both jogging and running. The effects of an effusion may be better observed in these activities as they place notable stress on the knee and require a greater activation of the quadriceps to control the knee joint.