An Overview of a Dog’s Joints & Ligaments

WHAT MAKES UP A JOINT?

The normal synovial joint is made of:

BONES

LIGAMENTS:

• Sheets, cords or bands of fibrous connective tissue that connect bones or cartilage
• Can be found either inside or outside the joint capsule

JOINT CAPSULE:

• Bound by a tough fibrous capsule, which contributes to the mechanical stability of the joint
• Lined inside by a very thin synovial membrane that functions to supply nutrients, joint fluid and to mediate immune or inflammatory processes
• Both the fibrous capsule and the synovial membrane have nerve and blood supply

SYNOVIAL (LUBRICATING) FLUID:

• Transparent, viscous fluid which bathes the joint
• Lubricates the joint, reducing friction between articulating surfaces
• Also supplies nutrients and removes waste from cartilage, which has very poor blood supply of its own

ARTICULAR CARTILAGE:

• Lines and protects the articular surfaces of bones in a joint
• Flexible, compressible type of connective tissue that is more resilient than bone
• Reduces friction between articulating bones
• Cushions the bones by acting as a shock absorber

THREE DIFFERENT TYPES OF JOINTS

Joints may have large ranges of movement such as the shoulder and hip joints, or have very little movement such as the joints between the bones in the skull. These joints are:

• Synovial: They allow free movement, such as knees, elbows and wrists. Synovial joints are the most numerous in the body and the most susceptible to inflammatory disease.
• Cartilaginous: As the name suggests, these are between cartilage, for example the vertebrae. There is some movement.
• Fibrous: Since these are connected with fibrous tissues, the length of the fibres will determine movement capabilities. Typically movement is none or very limited.

FUNCTIONS OF JOINTS 

The skeletal frame on its own is not flexible and needs help to move and absorb shock. Joints connect bones within the body, bear weight and enable movement. Without the right support, bone ends are prone to breakage caused by dislocation and excessive movement. Fortunately, bone ends are bound by ligaments.

JOINT AND LIGAMENT DISEASES IN DOGS

Some common diseases of joints and ligaments in dogs are:

• Dislocation of the hip, usually caused by trauma, causing lameness.
• Osteoarthritis (OA) or degenerative joint disease (DJD) is a common condition in which the joints become inflamed, swollen and painful. Symptoms can range from slight stiffness to loss of mobility. View More
• A collapse of the wrist can result from carpal hyperextension injuries, for example, jumping from an unnatural height and landing on the front legs.
• Hip dysplasia is an abnormal hip joint development that causes progressive lameness, stiffness and pain (more common in larger and giant breeds).
• Rupture of the cruciate ligament in the knee.
• Septic arthritis, a bacterial infection within a joint, can lead to systemic illness.

EVALUATION OF JOINTS AND LIGAMENTS

Diagnostic tests used to evaluate joints may include:

• Routine lab tests including blood and urine tests as well as immune tests.
• Orthopedic examination: simply use arms and hands to test motion capabilities.
• Regular X-rays can pick up dislocation, arthritis, hip dysplasia, joint effusion and other joint abnormalities.
• Arthrography, a type of contrast X-ray, relies on injected dye for enhanced assessment.
• Arthroscopy: typically, a knee or shoulder examination via a small scope inserted into a joint.
• Arthrocentesis: a microscopic examination and bacterial culturing of fluid drained from the joint.
• MRI and CT scans as well as surgical exploration are other (more costly) options to help diagnose abnormalities.

HELP MAKE YOUR DOG MORE COMFORTABLE

When pets are happy, pet owners are happier too, so don’t ignore canine joint or ligament abnormalities, even if they seem minor. If you are concerned about your dog’s joints and movement, seek the advice of your veterinarian.