There is provided a rate responsive biasing element 10 comprising a longitudinal connection member 20, a first location member 30 coupled to the longitudinal connection member 20, and a biasing means 41,42 located between the first location member 30 and a second location member 35 to provide a biasing force between the first location member 30 and the second location member 35. The biasing means comprises a rate-independent component and 41 a rate-dependent component 42 arranged to act in parallel. The rate independent component may comprise a spring. The rate dependent component may comprise a non-Newtonian material preferably a shear thickening fluid. The rate components may form annular members concentric relative to one another or may comprises a resilient material with a cavity containing the rate dependent component. The rate responsive biasing element 10 may form part of a prosthetic knee joint.
