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I think I can resolve the issues raised by Mark Swanepol and Geoffrey
Walsh. Our group found no apparent increase in joint stiffness in RA
despite what the patients were telling us. I thought at the time that
it might be perceived stiffness due to aberrant mechanoreceptor
activity and I did in fact proceed to look at vibration thresholds
(as a surrogate for proprioception) in this group - no abnormalities
(Helliwell Clinical Rheumatology 1994 13:51-53).
Measuring the passive mechanical properties of joints in vivo is
complicated by the structures which impact on and control joint
movement and about 50% of stiffness in the metacarpophalangeal joint
at mid range is due to forearm muscles. Unfortunately muscular
wasting occurs in RA (Helliwell Annals of Rheumatic Diseases 1994
53:726-728) so that when comparing joint stiffness between RA and
normals you have to correct for the decreased contribution of muscle
- once this is done people with RA are found to have increased
stiffness (Helliwell, Smeathers, Wright. Proc Institute Mech
Engineers 1994 208:223-228). So joint stiffness in RA is not an
enigma after all and it may be used to test the efficacy of
treatments in this group (Helliwell Annals of Rheumatic Diseases
1997 56:71-73). Incidentally a group from Holland looked at the
relationship between weather and joint stiffness. They measured
mechanical joint stiffness over aperiod of time and correlated
changes with barometric pressure - see Rasker et al Scandinavian
Journal of Rheumatology 1986 15:27-36.
Philip Helliwell, Senior Lecturer in Rheumatology,
Rheumatology and Rehabilitation Research Unit,
36, Clarendon Road, LEEDS, LS2 9NZ, UK
Tel: +44 113 2334935 Fax: +44 113 2445533
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Walsh. Our group found no apparent increase in joint stiffness in RA
despite what the patients were telling us. I thought at the time that
it might be perceived stiffness due to aberrant mechanoreceptor
activity and I did in fact proceed to look at vibration thresholds
(as a surrogate for proprioception) in this group - no abnormalities
(Helliwell Clinical Rheumatology 1994 13:51-53).
Measuring the passive mechanical properties of joints in vivo is
complicated by the structures which impact on and control joint
movement and about 50% of stiffness in the metacarpophalangeal joint
at mid range is due to forearm muscles. Unfortunately muscular
wasting occurs in RA (Helliwell Annals of Rheumatic Diseases 1994
53:726-728) so that when comparing joint stiffness between RA and
normals you have to correct for the decreased contribution of muscle
- once this is done people with RA are found to have increased
stiffness (Helliwell, Smeathers, Wright. Proc Institute Mech
Engineers 1994 208:223-228). So joint stiffness in RA is not an
enigma after all and it may be used to test the efficacy of
treatments in this group (Helliwell Annals of Rheumatic Diseases
1997 56:71-73). Incidentally a group from Holland looked at the
relationship between weather and joint stiffness. They measured
mechanical joint stiffness over aperiod of time and correlated
changes with barometric pressure - see Rasker et al Scandinavian
Journal of Rheumatology 1986 15:27-36.
Philip Helliwell, Senior Lecturer in Rheumatology,
Rheumatology and Rehabilitation Research Unit,
36, Clarendon Road, LEEDS, LS2 9NZ, UK
Tel: +44 113 2334935 Fax: +44 113 2445533
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To unsubscribe send UNSUBSCRIBE BIOMCH-L to LISTSERV@nic.surfnet.nl
For information and archives: http://www.bme.ccf.org/isb/biomch-l
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