Original articleThe initial effects of knee joint mobilization on osteoarthritic hyperalgesia
Introduction
The application of passive accessory movements to painful joints has long underpinned manual therapy practice. Although spinal and peripheral joint mobilization continues to be applied extensively in clinical practice, there is little experimental data to substantiate its effectiveness in reducing pain or improving function. Evidence for the efficacy of lower limb mobilization is particularly scarce, with the majority of studies of peripheral joints using an upper limb model (Vicenzino et al., 1996; Paungmali et al., 2003). To date, just two studies explore the hypoalgesic effects of lower limb mobilization, both of which focus on the ankle joint (Collins et al., 2004; Yeo and Wright, 2004). There is consequently an urgent need for further lower limb studies.
Although scientific literature has begun to characterize the effects of spinal manual therapy (Koes et al., 1996; Haldeman, 1999; Wright, 2002), there are only a few studies which investigate the hypoalgesic effects of peripheral joint mobilization techniques. In subjects with sub-acute ankle injury, an antero-posterior (AP) mobilization of the talo-crural joint immediately and significantly increased pressure pain threshold (PPT) and increased dorsiflexion range of motion (Yeo and Wright, 2004). This mobilization-induced hypoalgesia was significantly more effective than either an identical procedure involving static manual contact, or a control procedure with no contact. Using similar methodology for subjects with lateral epicondylalgia, an elbow mobilization with movement technique significantly reduced hyperalgesia more effectively than either the manual contact or no-contact control procedures (Vicenzino et al., 2001). Similarly, in an animal study, knee joint mobilization reduced capsaicin-induced hyperalgesia when compared to either manual contact or no-contact control procedures (Sluka and Wright, 2001). These results, from humans and animals, support the hypothesis that peripheral mobilization reduces hyperalgesia both locally and at a distant site.
Few studies have investigated the initial effects of mobilization on motor function. Vicenzino et al. (2001) found that elbow mobilization with movement not only reduced pain but also increased pain-free grip strength in subjects with chronic tennis elbow. A similar increase in pain-free grip strength was found following a cervical glide mobilization in a similar subject group (Vicenzino et al., 1998). In a study of subjects with chronic, non-specific neck pain, Sterling et al. (2001a) found that cervical mobilization decreased hyperalgesia and also reduced over-activity of the superficial neck flexors during the cranio-cervical flexion test, suggesting improved activation of deep cervical flexor muscles. There have been no studies exploring the effects on motor function of lower limb joint mobilization.
A number of mechanisms have been proposed to explain how the hypoalgesic effects of passive joint mobilization may be mediated. Local mechanical disturbance may modify the chemical environment and thereby alter concentrations of inflammatory mediators (Sambajon et al., 2003). Movement may also trigger segmental inhibitory mechanisms (Melzack and Wall, 1999). In addition, it has been hypothesized that mobilization may activate descending pain inhibitory systems, mediated supraspinally (Wright, 2002; Souvlis et al., 2004). Human studies have demonstrated that joint mobilization produces rapid hypoalgesia with concurrent sympathetic nervous system and motor system excitation, a pattern similar to that generated by direct stimulation of the periaqueductal gray matter (Vicenzino et al., 1998; Sterling et al., 2001a). Recent animal studies show that the analgesia produced by knee joint mobilization involves serotonin and noradrenaline receptors in the spinal cord, thereby supporting a role for descending pain modulatory systems (Skyba et al., 2003). There is, however, a need for further studies to analyse the respective roles of local, segmental and supraspinal mechanisms in the mediation of hypoalgesia following joint mobilization.
There is little experimental data exploring the initial effects of lower limb joint mobilization. The purpose of this study therefore was to investigate the immediate effect of passive knee joint mobilization on measures of pain and function in individuals with chronic knee osteoarthritis. In addition, the study sought to explore in humans the animal model of mobilization-induced hypoalgesia demonstrated by Sluka and Wright (2001). Consequently, methodology similar to that used in previous clinical and animal models of joint mobilization was applied, whereby the effects of 9 min of joint mobilization were compared with those of manual contact and no-contact control procedures (Vicenzino et al., 1998, Vicenzino et al., 2001; Yeo and Wright, 2004; Sluka and Wright, 2001).
Section snippets
Methods
The study employed a double-blind, controlled, repeated-measures design, with all within-subject factors.
Data management and analysis
Data were analysed using SPSS statistical package (version 11.0, SPSS, Chicago, Illinois). The alpha level was set at .
Results
Comparability between pre-condition PPT means was evaluated, with no significant difference found between treatment, manual contact control and no-contact control conditions (, ). Baseline data was also analysed according to day of testing. Again, no significant difference was found (, ), suggesting avoidance of systematic bias. In order to evaluate carry-over effects between sessions, WOMAC pain data were analysed for differences between mean values for 24 h
Effects on pain-related measures
This study established that 9 min of accessory mobilization of the tibio-femoral joint immediately increased knee PPT significantly more effectively than either manual contact or no-contact control procedures, in subjects with mild to moderate knee osteoarthritis. Mobilization increased knee PPT by 27.3%, compared with 6.4% resulting from manual contact, indicating appreciably reduced sensitivity to mechanical pain. This corresponds with evidence from spinal mobilization studies (Vicenzino et
Conclusion
The purpose of this study was to investigate the initial effects on pain and function of lower limb joint mobilization. The study has provided new experimental evidence that accessory mobilization of a human osteoarthritic knee joint has both an immediate local and a more widespread hypoalgesic effect. This supports the response seen in animal studies (Sluka and Wright, 2001). Clinically therefore, joint mobilization may be an effective means of reducing osteoarthritic pain and may potentially
Acknowledgements
The assistance of the following colleagues is gratefully acknowledged: Associate Professor Kathy Briffa, Mr. Timothy Karajas, Perth Community Physiotherapy and Adjunct Associate Professor John Buchanan.
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