Steifheit

Steifheit is a German noun meaning stiffness or rigidity. In general usage the term describes a property of resisting deformation, and in technical contexts it covers phenomena in medicine, biology, and engineering that relate to how easily something can be bent, stretched, or moved.

In medicine, Steifheit commonly refers to joint stiffness, a reduction in range of motion often following inactivity or inflammation. Causes include inflammatory rheumatic diseases (for example rheumatoid arthritis and ankylosing spondylitis), degenerative disorders (such as osteoarthritis), injuries, muscle spasm, and neurological conditions. Morning stiffness is a notable feature of several inflammatory diseases. Diagnosis relies on history and examination; treatment targets the underlying condition and may involve physical therapy, regular exercise, heat or cold therapy, and medications such as analgesics and nonsteroidal anti-inflammatory drugs.

In engineering and biomechanics, stiffness is defined as the resistance of a structure or material to deformation; for linear-elastic materials it is the ratio of force to displacement, or equivalently stress to strain (Young's modulus). Stiffness depends on material properties, geometry, and boundary conditions, and it is a key parameter in design, safety, and energy storage. It is measured by static load testing, dynamic tests, or derived from material data.

In biology and botany, Steifheit can describe tissue rigidity related to cellular structure, turgor pressure, and hydration. In exercise physiology, perceived stiffness may result from muscle tone, fatigue, or recovery state.