, Juraj Payer2 and Manfred Herold3
(1)
National Institute for Rheumatic Diseases, Piestany, Slovakia
(2)
Fifth Department of Internal Medicine, Comenius University University Hospital, Bratislava, Slovakia
(3)
Department of Internal Medicine VI, Medical University of Innsbruck, Innsbruck, Austria
JAK Janus kinases (JAKs) are a group of intracellular tyrosine kinases that play an essential role in controlling cellular activities in response to extracellular cytokines. In mammals, the JAK family comprises four members: JAK1, JAK2, JAK3 and Tyk2 (tyrosine kinase 2). Inhibition of JAK activity has therapeutic application in the treatment of inflammatory diseases and cancer.
Janda hypermobility test – see Hypermobility test 2 (according to Janda).
Jansen-type metaphyseal chondrodysplasia An autosomal dominant hereditary metaphyseal chondrodysplasia with dysproportional nanism (dwarfism) and short and deformed limbs. The metaphyses have a shape resembling rickets. It may be confused with rickets in the neonate and infant. However, X-rays show visible prominent separation between the epiphysis and the metaphysis, especially at the distal end of the femur and proximal end of the tibia. During toddler age, spotty calcifications appear in the metaphysis, formed by a partially calcified cartilage protruding into the diaphysis. Besides the long bone involvement, the skull and spine can also be affected. There is usually generalised demineralisation of the skeleton. Laboratory tests show the same as in primary hyperparathyroidism, with the increased serum calcium and alkaline phosphatase levels and a low serum phosphate, but the serum concentrations of the parathormone (PTH) or PTHrP (PTH-related protein) are very low. Hypercalciuria and elevated hydroxyprolinuria are present. The aetiology is a mutation of the gene coding for the PTH/PTHrP receptor, which is then capable of self-activation without the presence of bound hormone.
Joint A point of interconnection of two or more bones that enables movement between them. The degree of movement depends on the type of joint.
The following types of joints are recognised:
Synarthroses: The joints without a cavity. Movement is very limited. The bones are interconnected by fibrous tissue or cartilage.
Fibrous articulations:
Syndesmosis: the bones are connected by dense fibrous tissue (sutures, distal tibiofibular articulation),
Gomphosis: dental alveoli connection with the help of collagen fibres (the teeth in bony sockets),
Cartilaginous articulations:
Synchondrosis: the bones are connected by hyaline cartilage (synchondrosis sphenopetrosa, synchondrosis manubriosternalis and xiphosternalis),
Symphysis: the bones are connected predominantly by a fibrous cartilage and a very small amount of hyaline cartilage (symphysis pubis, symphysis intervertebral). In the course of life, a cleft often appears in the fibrous cartilage of the symphysis. This articulation is called hemiarthrosis and is considered to be a transition form of a joint towards diarthrosis (e.g. the vertical cleft filled with synovial fluid – cavum symphysis in the fibrous cartilage of symphysis pubis – pubic symphysis, the clefts in the intervertebral discs of the cervical spine, uncovertebral clefts). Rigid connection of the bones by bone tissue is called synostosis.
Diarthroses: The joints with a cavity (cavum articulare) containing synovial fluid. The bones touch one another with the contact surfaces covered by a hyaline cartilage, except for the perimeter of contact surfaces where they are connected by fibrous tissue forming a joint capsule composed of dense collagen tissue lined by synovial membrane on the inside and strengthened by ligaments externally. Such joints are called synovial joints. The range of movement in them is substantially greater than with synarthroses.
Diarthroses whose mobility is substantially limited due to the shape of articular surfaces and strong ligaments are referred to as amphiarthroses (e.g. the proximal tibiofibular joint and the sacroiliac joint).
Joint and periarticular structures A complex functional unit consisting of articulating bones, intra-articular structures (menisci), articular capsule, solidifying ligaments, adjacent muscles, tendons, peritendon and bursae. Neuro-regulatory mechanisms from peripheral nerves to central nervous system, and arterial, venous and lymphatic systems belong to this unit. The basic physical examination consists of five tests:
1.
Inspection
2.
Palpation
3.
Active and passive movement examination
4.
Examination of physiological movements in the joint
5.
Muscle strength testing (ability of muscular resistance)
Joint involvement in syphilis Syphilitic arthropathies are arthritides occurring in syphilis.
► Clinical symptoms and signs
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