The lack of definition between the calf and the ankle, often unhelpfully called “cankles,” results from two distinct issues: the accumulation of localized fat (adipose tissue) or the retention of excess fluid (edema). Understanding this distinction is the first step in addressing the cause, as fluid buildup requires a different approach than fat accumulation. This article explains how to physically differentiate between these conditions and outlines the common reasons for ankle swelling.
Identifying the Cause: Fat Versus Fluid Retention
The most reliable way to determine if ankle enlargement is due to fat or fluid is by performing the “pitting test.” Edema occurs when fluid leaks from blood vessels and accumulates in surrounding tissues, making the area compressible. To check for this, gently press your thumb or index finger against the swollen area near the shin or ankle bone for several seconds.
If the pressure leaves a temporary indentation, or “pit,” in the skin after you lift your finger, this confirms the presence of excess fluid, known as pitting edema. The severity is sometimes graded by how deep the pit is and how long it takes to rebound. If the tissue springs back immediately without leaving any mark, the swelling is considered non-pitting.
Adipose tissue, or fat accumulation, feels softer and more uniform than fluid retention. When you press on an area of localized fat, the tissue will not leave a lasting indentation and will simply spring back once the pressure is released. This difference occurs because fat cells do not allow for the displacement of interstitial fluid in the same way that edema does.
Common Reasons for Ankle Swelling
Once you confirm the enlargement is due to fluid retention (edema), consider the likely causes. Many instances of ankle swelling are temporary and related to lifestyle factors affecting fluid balance and circulation. Prolonged periods of sitting or standing are a common culprit, as gravity causes fluid to pool in the lower extremities without muscle movement to pump it back toward the heart.
A diet high in sodium can lead to fluid retention throughout the body, including the ankles, as the kidneys work to retain water to balance the excess salt. Dehydration can paradoxically contribute to swelling, as the body attempts to hold onto its remaining water supply. Minor injuries, such as a sprain or strain, cause localized swelling as part of the body’s natural inflammatory response.
Hormonal fluctuations are a frequent cause of temporary edema, particularly in women. Swelling can occur before menstruation or during pregnancy due to increased blood volume and pressure on the pelvic veins. Various medications can also cause fluid retention as a side effect, including certain blood pressure drugs, steroids, and some hormone therapies. These common causes of edema are manageable through simple changes like elevating the legs, increasing movement, or modifying dietary salt intake.
Warning Signs Requiring Medical Attention
While many causes of ankle swelling are benign, specific symptoms must be recognized as warning signs of a serious underlying health condition. An immediate red flag is swelling that occurs suddenly and affects only one ankle, especially if accompanied by pain, redness, or warmth. This combination can suggest a deep vein thrombosis (DVT)—a blood clot in a deep vein of the leg—requiring urgent medical intervention.
Persistent or severe bilateral swelling can signal systemic issues affecting major organs. If swelling is paired with shortness of breath, chest pain, or heart palpitations, it may indicate heart failure, where the heart is not pumping blood effectively. Swelling that does not improve after several days of home care or elevation may also be linked to kidney disease, which impairs the body’s ability to remove excess fluid and sodium. It can also signal liver disease, which affects the production of proteins that keep fluid in the bloodstream. Any unexplained, persistent, or worsening ankle swelling should prompt a consultation with a healthcare professional.