Bone and Joint Disease Overview

Bone and Joint Disease

• Bone pathology encompasses a range of causes, including developmental, degenerative, anomalous, autoimmune, metabolic, nutritional, neoplastic, idiopathic, inflammatory, infectious, toxic, and vascular conditions.
• Bone physiology involves osteoblasts creating new bone, osteocytes as principal bone cells, and osteoclasts for bone resorption. Bone structure also includes organic components (type 1 collagen and proteoglycans, contributing to flexibility), and inorganic calcium phosphate (hydroxyapatite crystals) giving rigidity.
• Congenital bone diseases include chondrodysplasia-dwarfism. Developmental conditions include osteochondrosis/hip dysplasia, angular limb deformities, hypertrophic osteodystrophy, and pituitary dwarfism.
• Metabolic bone diseases include nutritional osteodystrophy (common in puppies on meat-based diets), hypervitaminosis A (cats fed exclusively on liver), and metabolic-renal hyperparathyroidism (mostly in toy breeds).
• Traumatic bone conditions include fractures, and periosteal reactions, particularly frequent in juvenile dogs.
• Infections can result in osteomyelitis, often following fracture repair; symptoms potentially include pain, lameness, swelling, and sinus tracts.
• Neoplasia commonly involves osteosarcoma, often localized "around the knee". Aggressive tumours often metastasise. Different types of bone tumours are fibrosarcoma (uncommon), Multiple myeloma (osteolytic lesions), synovial tumours (rare), solitary osseous plasmacytoma, and metastatic tumours.
• Diseases of unknown origin commonly affect dogs include Marie's disease, hypertrophic osteopathy, craniomandibular osteopathy, and panosteitis.

Diagnosis of Bone Disease

• Signalment (age, sex, breed) and owner observations (lameness, duration, worsening/improving, exercise effects, recent trauma) are crucial.
• Clinical examination includes checking for wounds, fragments of bone, palpable fracture, symmetry, muscular atrophy, posture, limb palpation (heat, pain, swelling), gait assessment, and if any other clinical diseases present.
• Key imaging methods include radiography, ultrasound, CT, MRI, scintigraphy, and biopsy.
• Computed Tomography (CT) creates 3D images from many 2D radiographic images.
• Magnetic Resonance Imaging (MRI) provides excellent soft tissue imaging, while being less detailed for bone structures.
• Bone biopsy helps determine the cause when neoplasia is suspected, and to guide treatment plan and antimicrobial therapy.
• Determining lesion location and distribution (monostotic, polystotic) aids diagnosis, since older animals are often associated with monostotic conditions and younger ones with polystotic.

Joint Disease

• Diarthroidial joints allow smooth, frictionless movement, relying on cartilage, collateral ligaments, fibrous capsule, synovial membrane, and synovial fluid.
• Congenital joint problems include hip and elbow dysplasia, OCD (osteochondritis dissecans), and patellar luxation.
• Neoplastic disorders (though less common) including osteoarthritis, cruciate ligament rupture, secondary to developmental problems are also found.
• Inflammatory and infectious disorders involve osteoarthritis, septic arthritis.
• Immune-mediated polyarthritis affects young dogs, often displaying multi-limb pyrexia.
• Clinical findings (pain, discomfort, joint swelling, reduced movement, crepitus, muscle atrophy, bone changes) and examining gait for lameness are important.
• Synoviocentesis (examination of synovial fluid) can aid diagnosis; normal appears pale yellow/transparent, high viscosity, low in white blood cells, and total protein. Abnormal is serous/turbid/reduced viscosity, and has high white blood cell count, with >90% neutrophils. Also assesses other synovial fluid components.
• Imaging like radiography and ultrasound is used in joint disease diagnosis. Arthroscopy gives a direct view of the joints, useful for elbow diagnosis and treatment.

Management of Bone and Joint Disease

• Management options vary depending on the underlying condition and owner expectations.
• Specific surgical treatments include TPLO (for cruciate ligament disease), TTA, and lateral suture.
• Conservative management for developmental osteochondrosis involves rest, controlling inflammation and reducing body weight, and adjusting Ca:P ration in the diet.
• Surgical management of osteochondrosis may entail removing a cartilage flap via surgery or arthroscopy.
• Analgesia, controlling inflammation, and managing damage are considerations.
• Treating septic arthritis might involve joint lavage, removing bacteria, debris, and inflammatory mediators. Joint fluid samples are useful for culture and sensitivity tests.
• Diagnosing and managing immune-mediated problems may involve identifying the underlying cause, giving immunosuppressive therapy, along with analgesia.