◊ Joints Affections ◊

AFFECTION OF THE JOINTS

Anatomical Consideration

The joint is an articulation between two or more bones. According to their normal range of motion, joints are most often classified into three main groups:

1-Synarthrosis (fibrous joints)

They are immovable joints as in the skull, where bone plates are held firmly to each other by fibrous elements.

2-Amphiarthrosis (cartilaginous joint)

They are slightly movable joints as articulation between the vertebrae where a flattened disc of fibrocartilage connecting the articulating surfaces with a fibrous capsule invests the entire structure.

3-Diarthrosis (synovial joints)

They are movable joints. Synovial, or true joints, vary with regards to the number of bones composing the joint, the amount and kind of mobility in them and the form of the joint surfaces. Synovial joints characterized by presence of articular cartilage, joint cavity and joint capsule lined by synovial membrane. Joints are held together by ligaments which can be extracapsular, intracapsular or be part of the joint capsule. Some joints include intra-articular plates of fibrocartilage between the articular surfaces. They form congruent articular surfaces, allow greater range of movement and diminish concussion. Examples are the menisci in the stifle joint or the articular disc dividing the temporomandibular joint. Intraarticular fat pads are located in some joints for protection.

Synovial joints consist of

1-Articular Cartilage

The articular cartilage forms a covering over the articular surface of the epiphyseal subchondral bone. The articular cartilage is avascular structure and has no nerve supply. It receives nutrition from the synovial fluid and subchondral bone. The collagen fibers of the matrix of the articular cartilage are orientated to withstand maximum stress and strain. Hyaline cartilage diminishes the effects of concussion and greatly reduces friction.

2-Joint Capsule

The Joint capsule consists of two layers, the outer fibrous layer which is thickened in parts to form ligaments and the inner layer or synovial membrane which is responsible for secretion and absorption of synovial fluid. The synovial membrane has a rich supply of arteries, lymphatics and nerves. Its inner surface is covered with fine villi. The synovial membrane covers all structures within the joint except the articular cartilages and menisci.

3-Synovial Fluid  

Synovial fluid is an ultra-filtrate of blood plasma that contains hyaluronic acid, proteoglycans, protein, white blood cells and other biomedical mediators. The main function of synovial fluid is to lubricate the joint and provide nutrition to the hyaline cartilage. Synovial fluid is normally clear, colorless to yellow, viscid, free from blood and does not clot after standing. It contains a few cells and present inside the joint in low amount according to the volume and type of joint. The quality of the synovial fluid deteriorates with joint injury and inflammation. Synovial fluid analysis is valuable in diagnosis of joint diseases.

4-Ligaments

Joints are held in place by intra-capsular, capsular or extra-capsular joint ligaments.

AFFECTIONS OF THE JOINTS

I-ARTHRITIS

Definition: -

Arthritis can be defined as inflammation of the joint. This inflammation may involve any or all of the components of the joint, which include the bones forming the joint, the articular cartilages, the joint capsule and associated ligaments.

Types: -

1-Traumatic arthritis (serous arthritis)

2-Osteoarthritis (degenerative joint disease, DJD)

3-Septic arthritis (Infectious arthritis)

1-Traumatic Arthritis (serious arthritis)

It is characterized by non-infectious inflammation of the synovial membrane and increased synovial fluid, which causes increased capsular pressure and swelling.

Causes: -

Direct trauma is the main cause of serious arthritis. Also trauma due to poor conformation which causes constant stress on certain joint may lead to serious arthritis.

Clinical Signs: -

1-Signs of acute inflammation at the region of the joint such as swelling, pain and heat

2-Distention of the joint capsule with synovial fluid

3-Aspirated synovial fluid appears to be normal

4-Radiographically the bony structure of the joint appear normal

5-Serious arthritis may resolute leaving normal joint or develop into osteoarthritis if it persist for long time

Treatment: -

1-Rest and immobilization: -

1-Until the joint has returned to normal function

2-Bandage support may also assist healing of an acutely damaged joint (however, prolonged immobilization may lead to muscle atrophy and adhesion formation within the joint)

3-Casting is only appropriate in cases of ligamentous damage.

2-Physical therapy: -

Hydrotherapy may be useful immediately after a traumatic joint injury. It is reasonable to assume that cold hydrotherapy is indicated in the acute stage of joint injury to retard the inflammatory processes of exudation and diapedesis and reduce edema. The application of ice is extremely beneficial as a primary treatment for the most acute joint injuries. After 48 hours hot hydrotherapy may be indicated to relieve pain and reduce tension in inflamed tissue. The vasodilatory effect can aid in both fluid resorption as well as providing phagocytic cells.

3-Intra-articular injection of corticosteroids:

Aspiration of the excessive synovial fluid and intra-articular injection of anti-inflammatory drug with a prophylactic dose of antibiotics, then apply pressure bandage.  

2-Osteoarthritis (degenerative joint disease, DJD)

Osteoarthritis is a chronic disorder of synovial joints characterized by progressive deterioration of articular cartilage, in some cases resulting in a readily detectable radiographic loss in joint space, and by reactive changes in the joint margin and joint capsule.

Causes: -

1-Primary condition occurs in joint with no known previous trauma or disease. The primary condition is best exemplified by the joint changes seen in older animals. Primary osteoarthritis is generally regarded as an aging phenomenon in which deterioration of the articular cartilage occur leading to the characteristic joint changes.

2-Secondary osteoarthritis is the result of some insults to the affected joint. Usually it is a local phenomenon rather than a systemic disease, although some systemic diseases that affect joints may ultimately lead to osteoarthritis. Osteoarthritis may follow serious arthritis, trauma, or due to poor conformation.

Clinical signs: -

The clinical signs will vary with the type and degree of osteoarthritis as well as with the degree of acute inflammation. In high motion joints with acute inflammation, there will be lameness, heat, swelling of the joint (synovial effusion) and pain on flexion. In more chronic cases joint enlargement is associated with fibrous tissue deposition (some bony enlargement may also be present), but acute inflammatory signs may persist to various degrees. There will be decreased motion.

The characteristic radiographic features of osteoarthritis include: -

1-Narrowing of the joint space and deformity of the joint space due to the loss of significant amounts of articular cartilage, allowing sub-chondral bone which is more radiodens than articular cartilage to come in closer contact, therefore giving the appearance of a narrow joint space

2-The joint capsule may be undergoing fibrotic change and sometimes calcification.

3-Osteophyte formation which appear as periarticular new bone growth arising from the margins of the articular surface where the joint capsule attaches

4-Sclerosis of sub-chondral bone is seen in more chronic cases of osteoarthritis and suggested that bone beneath the cartilage is being subjected to increased stress that normally is born by articular cartilage.

The changes vary according to the severity of osteoarthritis. Although, radiography is one of the diagnostic tools, joints appear free of radiographic changes does not mean it is free of articular disease.

Treatment: -

The choice of treatment and its effectiveness will depend on the stage of the disease and the degree of active inflammation present. The principles of treatment of osteoarthritis can be divided into three areas

1-The first is the prevention or treatment of any primary cause.

2-The second principle is the treatment of active soft tissue disease contributing to articular cartilage degeneration. This includes rest, physical therapy, anti-inflammatory drugs and joint lavage.

3-The third principle is the treatment of cartilage degeneration. This includes articular cartilage curettage, osteophyte removal, radiation therapy and surgical arthrodesis.

The specific treatment methods are: -

1-Rest

2-Joint lavage

3-Intra-articular corticosteroids are useful for the treatment of soft tissue inflammation and the inhibition of enzymatic damage.

4-Surgical curettage of diseased articular cartilage

5-Surgical arthrodesis: for many cases of end stage osteoarthritis, the only methods available for pain relief are total joint replacement or arthrodesis. Arthrodesis is satisfactory in low motion joints as the pastern joint.

3-Septic arthritis (Infectious arthritis)

Septic or infectious arthritis means inflammation of the joint as a result of bacterial infection in the joint.

Causes: -

1-Hematogenous infection: -

Hematogenous septic arthritis is most commonly observed in young animals associated with umbilical infection (joint ill). Septic arthritis may be associated with pneumonia, entritis, metritis, suppurative mastitis, or any other form of systemic infection. Intrauterine infection can occur.

2-Traumatic injury with local introduction of infection: -

Direct trauma is a common cause of septic arthritis in older animals.  Direct penetration of the joint is not essential; tissue destruction and cellulitis in the region of the joint can lead to an open joint and septic arthritis.

3-Iatrogenic infection: -

It is associated with joint aspiration, injection, or arthrotomy.

Clinical signs: -

In young animal with hematogenous infection, the disease is commonly polyarticular with the larger joints, mainly hock, stifle, carpus and fetlock primarily involved. In addition to the typical localizing signs of infectious arthritis, the problem may also be accompanied by osteomyelitis.

Localizing signs in septic arthritis include lameness which may be slight in the early stages but usually progresses rapidly to a nonweight-bearing type of lameness. There will be swelling and heat of the involved joint. Both periarticular soft tissue swelling and synovial effusion are components to the joint swelling. Periarticular swelling will range from edema and cellulitis in the acute case to fibrosis in the more chronic case with bony enlargement being seen at a later stage. A low grade fever may be present in adults with infectious arthritis. Foals with polyarthritis generally tend to have increased temperatures.

Traumatically induced infectious arthritis in adult tends to be associated with more diffuse soft tissue swelling. In some instances, animal presented with open drainage from the joint.

Radiograph should be performed immediately to eliminate traumatic damage to the bone or osteomylitis. Marked effusion is often apparent by observing an increased joint space on radiographic examination. Sequential radiographs are important to assess the degree of destruction. Lytic change in the bone can develop very quickly. As the disease progresses, radiographic changes include periosteal proliferation and narrowing of the joint space due to destruction of articular cartilage. Rather than diffuse narrowing of the joint space, punctuate areas of lysis may be seen. With further progression, generalized osteomyelitis develops in the subchondral bone, and the joint space widens again as bone is destroyed. The combination of osteomyelitis and marked periosteal proliferation may cause eventual ankylosis.

Synovial fluid analysis is the most definitive way of confirming the existence of infectious arthritis.

Treatment: -

Treatment of infectious arthritis is designed to eliminate the causative organism and remove the harmful enzymes and proteinaceous material that can damage the articular cartilage.

1-Systemic administration of broad spectrum antibiotics

2-Intra-articular injection of broad spectrum antibiotics

3-Needle drainage by application of a wide needle and aspiration of all contents then injection of antibiotics

4-Through and through lavage by application one needle above and a second needle below then a large amount of normal saline solution is injected from above and drained from below.

5-Distension irrigation technique is performed by injection of normal saline solution inside the joint cavity and left for short time then removed.

6-Arthrotomy and surgical debridement with partial synovectomy may be necessary to eradicate the infection.

7-Arthrodesis of the joint

8-Amputation of the limb in complicated cases of small animal

Prognosis: -

The prognosis for any case of infectious arthritis is never good because lack of response to treatment can occur. Even with early and correct treatment, problems can still develop. In general, response to treatment in neonated polyarthritis seems better than in adult animal but the success is certainly not completely.

II-OSTEOCHONDRITIS DISSECANS (OCD)

Definition: -

It is a degenerative disease of young horses due to vascular changes (ischemia) and demineralization of bone. The lesion involves articulation and may cause fracture of articular cartilage. The chance of healing decreases as the cartilage doesn’t remain intact (separates and allows necrotic bones to be free).

Signs: -

1-Distension of joint capsule

2-Radiographic irregularity in the outline of the bone followed by demineralization and fragmentation.

3-Complete destruction of the articular cartilage at late stages.

Treatment: -

OCD lesions are usually treated by surgical excision of the cartilage flap and curettage of the subchondral bone to stimulate bleeding and fibrocartilage filling of the bone defect.

III-DISLOCATION OR LUXATION OF THE JOINT

The joint is dislocated when the two articular extremities forming it are displaced from perfect contact with one another.

Types: -

1-Complete dislocation or luxation: The articular surfaces become in no part in contact with one another

2-Incomplete dislocation or subluxation: the articular surfaces are still partially in contact with one another

Causes: -

1-Severe violence as motor-car accident

2-Congenital as secondary to hip dysplasia

3-Pathological as in cases of paralysis of some muscles or in cases of arthritis

Clinical signs: -

1-Immobility of the affected joint. This is due to mechanical impossibility of the free movement of the articular extremities on account of their displacement.

2-Deformity is due to displacement of the bone extremities. A prominence is seen in one side and a depression may be seen in the other side. The limb takes abnormal direction.

3-A large inflammatory swelling may be seen in deep situated dislocation and tends to conceal the characteristic features of the condition.

4-A rocking sound or crepitation may be obtained on manipulation of the bones due to knocking of the articular ends against each other

5-Severe pain during passive manipulation of the joint

6-Muscular atrophy in chronic cases

Treatment: -

1-Closed reduction and fixation in recent cases within the first 24 hours

2-Open reduction and fixation in old cases

The treatment depends on the type of affected joint and is more successful in small animals than large animals.