RADIOLOGY OF SKELETAL SYSTEM Lecture 3 JOINTS

Radiological anatomy of the joint in the plain film The synovial joint have articular surface covered by the hyaline cartilage. Cartilage is of the same radiodensity as the soft tissues and ,therefore ,is not visualized as such; only the space between the adjacent articular cortices can be appreciated .

The commonly used expression (joint space) is in fact a misnomer as it is not a space at all but consist of articular cartilage and synovial fluid. The synovium, synovial fluid and capsule also have the same radiodensity as the surrounding soft tissues. The articular cortex forms thin well defined line which merge smoothly with the cortex of the bone .

Imaging technique : Plain film :is primary method of investigation of joint disease , but the MRI is being used with increasing frequency to show not only the surface of the intra-articular structures but also showing the meniscal and ligament tear (e.g. cruciate ligament of the knee joint) , rotator cuff tear in shoulder joint and the adjacent structures ( bone or muscles).

Ultrasonography High-frequency transmission of sound can be used to evaluate the soft tissues , tendons, ligaments, and even the cartilage of the joint. The ultrasound waves cannot be transmitted through cortical bone so the intramedullary cavity cannot be imaged with this technique.

Arthrography involved injection of C. M Arthrography involved injection of C.M. into the joint space and taken either plain film or CT scan ) for demonstration of mensical & ligament tear , but it is largely replaced by the MRI because it is invasive method .

Signs of joint disease by plain film Signs indicating the presence of the arthritis : 1- joint space narrowing : Due to destruction of articular cartilage , occur in all joint disease except in avascular necrosis. 2- soft tissue swelling :Swelling of the tissue surrounding joint may be seen in any joint disease accompanied by Joint effusion. The thickened synovium in synovial tumors haemophilia may give rise to striking soft tissue swelling . 3- osteoporosis: occur in the bone adjacent to joint specially in painful condition (underuse of bone seem to be an important factor in the osteoporosis.

Signs of joint disease by plain film Signs that point to the cause of arthritis : A--Bone erosion : there are several causes of erosions : 1-Inflammatory overgrowth of synovium which occurs in: rheumatoid arthritis - psoriasis - Reiter’s disease – Ankylosing spondylitis and Tuberculosis 2-Response to the deposition of urate crystals in gout .

Signs of joint disease by plain film Signs that point to the cause of arthritis : ( A-Bone erosion ) 3-Destruction due to infection : pyogenic arthritis &Tuberculosis . 4-Synovial overgrowth due to repeated haemorrhage in haemophilia and related bleeding disorders. 5-Destruction due to neoplastic overgrowth of synovium e.g. synviosarcoma.

Signs of joint disease by plain film Signs that point to the cause of arthritis : B- osteophytes , subchondral sclerosis and cyst : these are features of the osteoarthritis. C--Alteration in the shape of joint: occurs in slipped epiphysis & congenital hip dislocation

Rheumatoid arthritis Polyarthritis inflammatory disease seen at all age groups but especially from 20-55 y, more common in female than male . The disease typically involves small joints ( metatarsophalangeal , metacarpo-phalangeal and carpal joints ) , the axial joints is later and less often affected . The tendency at the peripheral joint to symmetry and often identical digits on either side of the body are affected .

Radiological finding(Plain film) 1-soft tissue swelling: it is the earliest sign due to oedema of the periarticular tissue and to synovial inflammation in bursa, joint distension also following increase in synovial fluid . In the hand, fusiform swelling due to capsular distension and local oedema may be seen over the interphalangeal joints and over the metacarpo- phalangeal joints. Soft-tissue changes are less well demonstrated in the foot.

Radiological finding(Plain film) 1-soft tissue swelling: Swelling around an affected joint is symmetrical, while in gout the swelling is eccentric. In rheumatoid arthritis : rheumatoid nodule may cause a localized eccentric swelling, and these often occur at pressure points, for example over the olcranon.

Radiological finding(Plain film) 2-osteoporosis: assessment of osteoporosis by compared the normal joint with abnormal one and is Increase with the duration of disease and age of the patient, it is precursor of erosion .

Radiological finding(Plain film) The osteoporosis either : Generalized :This may be due to steroids or limitation of movement due to pain or muscle wasting, and occurs later in the course of the disease. b. Localized :Local osteoporosis around joints occurs earlier and is due to synovial inflammation and hyperaemia.

Radiological finding(Plain film) 3- joint space change & alignment deformities In early stage a joint space may be widened by synovial hypertrophy and an effusion. Later in disease, joint spaces narrowing due to cartilage destruction. Alignment abnormalities at joints may result from local synovitis weakening the capsule and tendinitis preventing normal musculotendinous action.

Radiological finding(Plain film) 3- joint space change & alignment deformities Many changes of alignment in rheumatoid hand are irreversible but if due to local soft-tissue laxity, may be corrected by applied pressure. Subluxations at metacarpophalangeal joints lead to ulnar deviation

Radiological finding(Plain film) 3- joint space change & alignment deformities The boutonniere deformity results from proximal interphalangeal joint flexion and distal interphalangeal joint extension. The swan-neck deformity from the reverse (proximal interphalangeal joint extension and distal interphalangeal joint flexion), the boutonniere deformity is the more common.

Radiological finding(Plain film) 4- periostitis : Local periosteal reactions occur either along the midshaft of a phalanx or metacarpal as a reaction to local tendinitis or at the metaphysis near a joint affected by synovitis.

Radiological finding(Plain film) 5 –Erosion:These are most important diagnostic change but are not necessarily present when the patient first attends. Classic periarticular erosion occur at the bare-area ( the edge of the articular cartilage and attachment of the joint capsule ) . Erosions arise in an area of local demineralization beneath the cortex, which is progressively resorbed. On occasion, intraosseous defects-cysts or geodes 2-3 cm or more in diameter, may be seen beneath joint surfaces.  

Gout Caused by deposition of sodium biurate crystals , commonly affects small joints specially interphalangeal joint of big toe .

Radiological finding(Plain film) 1-Erosion: punched out in appearance ,they tend to appear near joint margins , as they enlarge, they tend to involve more of the cortex of shaft rather than the articular surface . Large erosions extend to the articular cortex. Cartilage destruction is relatively late manifestation.

Radiological finding(Plain film) 1-Erosion: Usually much bony destruction is seen before cartilage loss supervenes. In the hand, gout tends to attack the distal and proximal interphalangeal joint , while rheumatoid arthritis affects the metacarpo- -phalangeal and proximal interphalangeal joints.

2- Tophi : shown as soft tissue swelling eccentric in distribution ( in contra- distinction to the fusiform swelling of rheumatoid arthiritis ) , some time may be calcified

Radiological finding(Plain film) 3- Osteoporosis : not seen except in advanced cases which have been immobilized .

Osteoarthritis Is a degenerative condition affecting joints especially those which bear weight ( e.g. knee & hip joints ) or those subjected to much ( wear and tear ) , common at the large joint , virtually not affected the small joint. The disease either primary ( occurs in normal joint no underlying cause ) while secondary type if the joint is abnormal or subjected to unusual stresses.

Osteoarthritis The primary type is a familial arthritis that affects middle-aged women, while the secondary type involved any age group ,and equal in both sex .

Radiological finding(Plain film) 1- joint space narrowing : result from destruction of cartilage , is asymmetric , more common at the excessive weighted –bearing area ( medial part of knee joint , upper part of hip joint ) . 2- joint space remodeling : Joint narrowing due to cartilage destruction is followed by loss of underlying bone in stressed areas, and formation of new bone and cartilage in non-stressed area and at joint margins, so there is increase in density (seclrosis) , at the joint margins –peripheral osteophytosis , or within the joint central osteophytosis.

Radiological finding(Plain film) 3- loose bodies : formed by detachment of osteophytes,or ossification of cartilage debris 4- sub-articular cyst or geod formation : Large well defined lytic lesion with thin corticated margin in subarticular regions, relatively large ( up to 2-3cm ), this sign seen also in rheumatoid arthritis when affects large joint ( like knee or hip joint).

Subchondral Cyst or Geode of the Shoulder degenerative joint disease Subchondral Cyst or Geode of the Shoulder

Hallmarks of Degenerative Joint Disease : Osteoporosis and bony ankylosis are not manifestations of degenerative disease.  Hallmarks of Degenerative Joint Disease : Joint space narrowing Sclerosis Osteophytes  

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