Musculoskeletal ImagingSynovial joint
a type of specialized joint in which apposing bone surfaces are separated by a joint cavity lined by
synovial membrane.
Articular cartilage, usually hyaline in type, covers the ends of both bones, and the
synovial membrane secretes
synovial fluid into the
articular cavity. Some
synovial joints also have an intra-articular disc of fibrocartilage that divides the joint cavity partially or completely,
fat pad and
labrum. Other structures that may be associated with
synovial joints are the subchondral
endplate,
tidemark,
joint capsule,
tendon sheath,
bursa and
sesamoid bone.
Synovial joints generally allow unrestricted motion and occur predominantly in the appendicular skeleton. A morphological classification of
synovial joints is given in Table 1.
Synovial joint, Table 1. Morphological classification of synovial joints.
| Type of joint | Motion | Examples |
|---|
| Plane | Uniaxial | Intermetatarsal, intercarpal |
| Hinge | Uniaxial | Humeroulnar, interphalangeal |
| Pivot | Uniaxial | Proximal radioulnar, median atlantoaxial |
| Bicondylar | Uniaxial | Knee, temporomandibular |
| Ellipsoid | Biaxial | Radiocarpal, metacarpophalangeal |
| Sellar | Biaxial | First carpometacarpal, ankle, calcaneocuboid |
| Spheroidal | Triaxial | Hip, glenohumeral |
Adapted from Williams PL, Warwick R: Gray's Anatomy, 36th British Edition, Philadelphia, WB Saunders Co, 1980, p. 430.
Numerous musculoskeletal diseases lead to abnormalities of the synovial joints, among them rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, Reiters syndrome, calcium pyrophosphate dihydrate crystal deposition disease, osteoarthritis, gout, septic arthritis, trauma and tumour metastases. Soft tissue swelling, osteoporosis, joint space narrowing, bony ankylosis, erosions, cysts and bone proliferation or whiskering are typical findings.
DR