Heberden oration 1985. The rheology of joints.

The value of rheological studies of joint tissues has been illustrated by studies from our department. These have included studies of the stiffness of joints which suggest that subjective stiffness is more likely to be related to limitation of movement of a joint than to increased physical stiffness (either elastic or dissipative torques). A review of goniometry suggests that the diminution of joint movement with advancing age varies with the frequency of use of the joint. A simple goniometer for the hip has been described, and in contrast a sophisticated telemeterized system has been devised. Instruments to measure passive movement of joints, and their application for hypermobility, have been discussed. A knee analyser has been constructed to measure ligamentous and meniscal damage. Ligament replacement has been successfully achieved in the pig and in man by using a woven polyester tube. The load-bearing function of the menisci has been clearly demonstrated, explaining the relationship found in studies of parachutists and physical-education teachers between meniscectomy and osteoarthrosis of the knee. Support for the Leeds biomechanical hypothesis for the development of osteoarthrosis has been described from rheological studies of cartilage at the patellofemoral joint and at the ankle. The intervertebral joint does not appear to be a shock absorber in compression. The spine must bend to function in this way. The relevance to rigid segments of the spondylitic spine and surgical fusion of vertebrae is discussed.