Muscle Swelling in Cats


Muscle swelling can be defined as any abnormal increase in size of muscle tissue. Swelling is the direct result of a proliferation of muscle cells, inflammatory cells, or bodily fluids and is caused by a number of injuries and disorders.


The causes of muscle swelling vary widely from minor injuries to some types of cancer, so the associated level of concern varies accordingly. A small area of swelling present without any other symptoms is of little concern, whereas larger swellings or swellings accompanied by symptoms like:

• Pain

• Distress

• Appetite loss

• Lethargy

are more concerning. Consultation with a vet is recommended if a cat is showing any of these symptoms whether muscle swelling is present or not.

Possible Causes

Muscle swelling in cats commonly indicates

• the presence of a tumor/growth near the area

• damage to the muscle from physical trauma; such as blunt force or a cut

• inflammatory disorders (Polymyositis, Dermatomyositis though these are rare in cats)

Risk Factors

Muscle swelling in cats can be described as:

• Generalized or focal: throughout the body or in one small area

• Acute or chronic: recently noted or ongoing

• Mild or severe

• Primary or secondary: the swelling arises solely in the muscle where it is noted or as the result of another condition

Testing and Diagnosis

The following diagnostic tests are performed to determine the underlying cause for muscle swelling and the best course of treatment:

• Physical examination: palpation of the affected area

• Blood work: indicates many types of possible illness including infection and some cancers

• Diagnostic imaging: may include X-ray, MRI, CT scan depending on what other symptoms are identified

• Fine needle aspirate to collect cells from the swollen area for microscopy analysis

• Biopsy: a small sample of tissue is taken from the affected area for analysis

Similar symptoms

Anything that causes swelling under the skin can be confused for muscle swelling. Some causes of swelling in cats include: 

• Abscess: swelling caused by infection

• Tumor: a mass of cells growing abnormally

• Granuloma: small masses of inflammation or cell growth

• Hematoma: deep bruising

• Foreign body: may become embedded in tissue due to injury

Muscle swelling may be mistaken for localized inflammation of other tissues near the muscle, like bone or connective tissue.

Associated Symptoms

Muscle swelling is often observed alongside lethargy, pain in affected area, and reduced movement using affected muscle.

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