Cat Bone Structure and Function

The feline skeleton is an amazing structure that gives the body shape, strength, and mobility. It forms the rigid framework that supports the cat’s muscles and organs, protects delicate internal structures, and even plays a key role in producing blood cells. Below is an overview of how the cat’s skeleton is built, what it does, the types of diseases that can affect it, and how veterinarians evaluate skeletal problems in cats.

What Is the Skeleton?

The skeleton is the bony framework found in all vertebrate animals, including cats and dogs. It is made up of bones, ligaments, and cartilage — the hard tissues that support the body. The skeleton provides several essential functions: it supports body weight, protects major organs, allows movement by acting as a system of levers for the muscles, and produces red blood cells through a process called hematopoiesis. On average, a cat’s skeleton contains about 250 bones.

Although the feline skeleton is similar to the human skeleton, there are a few important differences. Cats have more bones in the spine than humans, primarily due to their tails. Their vertebrae are also more loosely connected, which makes the spine extremely flexible.

This flexibility is what allows cats to arch their backs, twist their bodies, and squeeze through very small spaces. Another key difference is that cats lack a true clavicle (collarbone). Without this bone, the shoulders can move more freely, which increases stride length and helps cats slip easily through narrow openings.

Where Is the Skeleton Located?

The skeleton extends throughout the entire body — from the skull in the head to the bones of the spine, ribs, tail, and limbs.

What Is the General Structure of the Feline Skeleton?

The feline skeleton is divided into three main parts. The axial skeleton includes the skull, spine, ribs, and sternum. The appendicular skeleton consists of the bones of the limbs. The visceral skeleton includes small bones that form part of certain organs, such as the tiny ossicles in the middle ear.

Bones themselves are living organs made of mineralized tissue that provide strength and structure. Their size and shape can vary depending on breed, since selective breeding has influenced skeletal structure over thousands of years.

Bones are also classified by shape. Long bones are found in the limbs, while short bones are located in areas like the wrists and ankles. Sesamoid bones are found near freely moving joints.

Flat bones protect delicate structures and provide attachment points for muscles, such as those in the skull and pelvis. Irregular bones include the vertebrae and certain skull and hip bones.

Each bone contains multiple layers. The outer surface is covered by the periosteum, a fibrous membrane rich in blood vessels that nourish the bone. Beneath this is cortical (compact) bone — a dense, strong layer that makes up about 80% of the skeleton and bears most of the body’s weight. Inside the bone lies cancellous (trabecular) bone — a spongy, honeycomb-like structure that provides strength while remaining lightweight.

Deep within the center of many bones is the medullary cavity, which contains bone marrow. Yellow marrow is rich in fat, while red marrow is responsible for producing red and white blood cells. Red marrow is primarily found in bones such as the femur, humerus, pelvis, and ribs.

What Are the Functions of the Feline Skeleton?

The cat’s skeleton serves four vital roles. It supports and protects the body, forming a rigid shield around organs such as the heart, lungs, and brain. It acts as a lever system for muscles, allowing movement.

It stores important minerals — especially calcium and phosphorus — which can be released into the bloodstream when needed. And finally, the skeleton is a major site of blood cell production and fat storage within the bone marrow.

What Diseases Affect the Skeleton?

Although the skeleton is strong, it can still be affected by disease, trauma, nutritional problems, and developmental abnormalities. Some skeletal disorders are congenital, meaning they are present at birth. Examples include mucopolysaccharidosis VI, a rare metabolic disorder most commonly seen in Siamese cats that leads to bone deformities and lameness, and osteodystrophy in Scottish Fold cats, which causes painful bony changes in the tail, toes, and limb joints. Another condition, multiple cartilaginous exostoses, involves abnormal bony growths that develop along long bones, ribs, and vertebrae in young adult cats.

Infection of the bone, called osteomyelitis, may occur when bacteria or fungi invade bone tissue — sometimes following trauma, surgery, or the placement of orthopedic implants. Nutritional disorders can also weaken bones. Rickets develops when kittens are fed diets deficient in calcium or improperly balanced foods such as all-meat diets.

Chronic kidney disease may cause mineral imbalances that soften and weaken bone. Vitamin D deficiency, or inadequate sunlight exposure to support vitamin D metabolism, can also lead to skeletal deformities and fractures. On the other hand, excessive vitamin A — often seen in cats fed mainly liver — can cause bone deformities, stiffness, and pain.

Trauma is one of the most common causes of skeletal injury in cats, especially those allowed outdoors. Falls, fights, and vehicle accidents frequently result in fractures or dislocations. Bone cancer is less common in cats than in dogs, but tumors can still arise either within the bone or spread there from other areas. Cats are more likely than dogs to develop cancers involving the bone marrow, such as lymphosarcoma.

How Is the Skeleton Evaluated?

When a cat presents with bone or joint problems, the veterinarian will begin with a thorough physical exam, carefully feeling the bones and joints and observing the cat’s gait for signs of lameness or pain. X-rays are one of the most important tools for viewing bone structure, since both cortical and cancellous bone are well-visualized on radiographs. Depending on the situation, sedation or anesthesia may be needed to keep the cat still for accurate imaging.

Blood tests such as a CBC and biochemistry panel can help detect infection, anemia, mineral imbalances, or systemic illness such as kidney disease. If infection is suspected, samples may be collected for bacterial or fungal culture.

In some cases, vitamin D, vitamin A, or hormone levels are measured. A bone biopsy may be required to diagnose tumors, infections, or congenital disorders. Bone marrow biopsies are used when bone marrow disease is suspected.

Advanced imaging, including CT scans, MRI, or nuclear bone scans, may be recommended to evaluate complex skeletal or soft-tissue problems. Chest X-rays are also commonly taken to look for tumors or infections that may have spread to the lungs or to evaluate rib and vertebral health.