In medicine, the term mobility is usually associated with the joints of the body. The extent of mobility is indicated for joints by the neutral-zero method. Joint stiffness can be documented in this way.
What is mobility?
In medical usage, mobility is often associated with the joints of the body. Numerous movement processes occur in the human body. Many of these are involuntary and thus beyond our control, such as the so-called peristalsis of the esophagus, intestines, stomach, and ureter, or the movement of the respiratory muscles and heart muscle. Medicine usually distinguishes involuntary movement processes from active movement in the sense of motor activity. Involuntary movement processes are sometimes referred to as motility. Mobility, in turn, is to be distinguished from motility. In the narrower definition, this mobility corresponds to passive mobility and thus refers to the physical property of being able to be made to move passively. In medical usage, mobility is often associated with the joints of the body that can be passively moved. The neutral-zero method is used to measure this mobility. In its expanded meaning, however, the medical term mobility does not stand exclusively for the passive ability of joints to move, but encompasses all forms of mobility. In this context, the term may refer, for example, to the ability to move independently, as in neurology. In addition, the broader meaning of the term includes the ability of tissues to move, as checked during palpation.
Function and task
In the narrow definition, medicine uses the term ‘mobility’ or ‘mobility’ to refer to the numerous joints of the body that can be moved passively. In clinical practice, the mobility of individual joints is determined using the neutral-zero method and reported as an orthopedic index. In the method, the mobility of the joint corresponds to a three-digit code. Passive motion takes place from the neutral zero position of the joint and is expressed in angular degrees from this position. The first digit of the three-digit code describes a movement away from the center of the body. Such types of movement include extension, abduction, pronation, retraction, ulnar abduction, elevation, and retroversion or horizontal extension. The second digit differs from zero only if the respective joint cannot be passively brought into normal zero position. If the joint can no longer assume this initial position, the zero is given either before the minimum flexion or after the minimum extension of the joint. The third digit represents movements that lead to the body. These include flexion, adduction, and supination. In some cases, the range of motion is also given in the opposite direction. Some joints have more than one axis of motion and then require multiple three-digit codes to indicate overall mobility. For example, a healthy hip joint is capable of extension and flexion with values of 10-0-120. The values for abduction and adduction are 45-0-30, and external rotation and internal rotation are 50-0-40. If mobility is limited in terms of abduction or adduction, a joint could have a value of 180-90-0, for example. In this case, the range of motion on the corresponding axis is only 90 degrees.
Diseases and complaints
The neutral-zero method is capable of documenting the restricted mobility of joints. Restrictions in mobility are present in the context of various diseases, such as deformities or after accidents. Mobility is also severely reduced in the case of joint stiffness or joint rigidity. Joint stiffness can generally affect all joints of the body. In most cases, however, joint stiffness affects the fingers, knee joints or elbows. Joint stiffness is acute, for example, after accidental injury, or occurs chronically with various diseases. The degree of severity depends on the cause and can vary from slight movement restrictions to complete immobility. Two types of joint stiffness are distinguished.One of them is contracture, in which the joint itself is not damaged and basically the connected ligaments, muscles or tendons are the cause. Ankylosis also corresponds to a joint stiffness. Damaged joints and bones are the cause for this type of mobility restriction. In individual cases, joint stiffness may occur as a result of bed rest. The lack of movement of joints in a plaster cast, for example, often leads to a restriction of their mobility because the tendons, ligaments or muscles shorten as part of the lack of movement. However, joint stiffness is much more common in the context of disease. One of the most significant diseases in this context is gout. Equally common is osteoarthritis, which degenerates the joints themselves and, like gout, causes severe pain. Osteoarthritis must be distinguished from age-physiological wear and tear. Only wear and tear above the age-physiological level is considered manifest arthrosis, which is primarily promoted by misalignments and incorrect stresses. The mobility of the joints can correspond to a complete immobility due to arthrosis. In contrast, age-physiologic joint stiffness does not usually result in complete immobility.
