A Finger Arthrograph for the Quantification of Joint Stiffness

The quantification of joint laxity in dancers and gymnasts

The aim of this study was to determine the range of movement in gymnastic and dance populations. Sixty-five participants (41 females, 24 males; mean age 21.4 years) were assessed. The sample included dancers and gymnasts ranging from novice and club standard to international and professional status. Non-specialized physical education students acted as controls. Range of movement was measured at the shoulders, hips, lumbar spine and ankles using a Loebl hydrogoniometer, and inherent joint laxity was assessed using Beighton and coworkers' adaptation of the Carter and Wilkinson 9-point scale. The right and left sides of the body were assessed and measures of active and passive motion were recorded. A graded increase in laxity was observed from controls, through novice gymnasts, to dancers and finally international gymnasts. The greater laxity of females than males was also confirmed. Dancers and gymnasts had a greater passive range of movement in all joints, which was partly inherited and partly acquired. There was a large difference between their active and passive ranges, which appeared to render the joints unstable.

A review of some of the rheumatological problems and engineering capabilities

Up to 150 different diseases can affect the joints and musculoskeletal system. These range from musculoskeletal rheumatism, which is self-limiting and causes no demonstrable joint pathology, through metabolic and degenerative joint diseases to the chronic auto-immune disorders of inflammation of which rheumatoid arthritis is the most common in the United Kingdom, and the most severe.

Many of these conditions are characterised by inflammation which has the cardinal symptoms of heat, swelling, pain, erythema, and loss of function. Rheumatologists require accurate and objective methods of measuring all these parameters at a large number of joints, each of different anatomical structure, in order to adequately monitor the course of the disease and its response to treatment. Complementary information is required on the function of muscles, ligaments, tendons, and bone, as well as the joints. Although the individual analysis of each of these components is likely to provide the most information on disease pathogenesis, functional evaluation which integrates many of these variables simultaneously is likely to provide most information on the patient's progress. Both are needed.

In the realm of therapeutics, a wide range of prostheses, all of sound bioengineering design, are available. Greater problems arise in the matching of different prostheses to an individual patients needs and in their fixation in a patient whose disease is constantly altering the joint contour. The attention of bioengineers is now being directed towards the design of replacements for other parts of the joint and musculoskeletal system, for example, ligaments. Adequate methods of testing these under repetitive stress and of measuring the improvement they provide will be increasingly required.

A clinical review of the hyperlaxity of joints with particular reference to osteoarthrosis

The range of observed movement at a given joint varies with a gaussian distribution throughout the population. Individuals whose joints display an unusually high degree of laxity are susceptible to a variety of rheumatic and orthopaedic symptoms. The impression that such individuals develop premature osteoarthrosis is a strong one, but hard to prove. In addition, certain individuals with inherited abnormalities of connective tissue are undoubtedly at risk of accelerated osteoarthrosis.

The observed range of movement at a joint is determined by a variety of factors. The main ones are the muscular tone, the laxity of the collagen that contributes to the joint capsule and surrounding structures, and the shape of the articulating bony surfaces. The first of these is probably neurologically mediated, the latter two are usually genetically determined. In a majority of cases it is probably the mechanical joint instability that produces the articular damage, though the alternative hypothesis is that the osteoarthrosis is initiated by genetic aberrations in the collagen that coincidentally cause lax joints. Clinical and family studies using the Leeds Hyperextensometer will help to clarify this and it remains a possibility that genetic markers may point to those individuals who will be at particular risk of osteoarthrosis should joint hyperlaxity develop.

Influence of weather on stiffness and force in patients with rheumatoid arthritis

A simple instrument has been developed for quantitative measurement of stiffness (elasticity) and maximum force of the fingers and was tested in a series of 122 out-patients with RA and 101 healthy controls. Values measured for stiffness were higher in RA patients and were scattered more widely than in controls and the mean values for force in the RA patients were lower than in controls. RA patients with an elevated ESR have significantly less strength than those with low ESR. We evaluated the influence of the time of day and weather (humidity and air temperature on the wards and outside the hospital, barometer pressure) on stiffness and force. In 13 in-patients with definite or classical RA and 12 controls, measurements were performed in the morning and afternoons, over periods of 3 weeks. In RA patients, both stiffness and force increased with outside air humidity (p less than 0.05), confirming the clinical experience that stiffness increases in damp weather. In the controls, force decreased with a higher air humidity on the wards (p = 0.05) and increased with higher barometer pressure (p less than 0.05). In the controls joint stiffness was higher in the morning than in the afternoon (p less than 0.05). In the RA group, rather unexpectedly, the reverse was found (p = 0.06), possibly explained by the time of the day the investigation was done. Only in the controls was a significant increase in force noted during the 3 weeks of investigation (p less than 0.005). No correlation was seen between force and stiffness. No correlation was found between disease activity as expressed in ESR, Hb, Rose titre, ARA grading and stiffness or force.