A ganglion cyst is a non-cancerous, fluid-filled lump that commonly develops underneath the skin, typically near joints or tendons. These cysts are usually harmless and often contain a jelly-like substance similar to the fluid that lubricates joints. While their exact cause remains unknown, they are among the most frequently encountered soft tissue masses.
Common Sites of Ganglion Cysts
Ganglion cysts most frequently appear in areas of the body that experience repetitive motion or stress, particularly around joints and tendons. The wrist is the most common location, with cysts often forming on the back (dorsal aspect) or the palm side (volar aspect). Dorsal wrist ganglions typically arise from the scapholunate ligament, while volar wrist ganglions may originate from the radiocarpal or scaphotrapezial joints. These cysts can range in size and may become more noticeable with increased joint activity.
Beyond the wrist, ganglion cysts are also common on the hands and fingers. They can develop near any finger joint, including the last joint closest to the fingernail, where they are sometimes called mucous cysts and are often associated with arthritis. Cysts may also form at the base of the finger on the palm side, often feeling firm and pea-sized. Their frequent occurrence in these areas is linked to the intricate network of joints and tendon sheaths.
The feet and ankles represent another common site for ganglion cysts. These can appear on the top of the foot, often near the base of the toes or around the midfoot. Cysts may also form near the ankle joint, typically on the front or side, or occasionally on the sole of the foot. Like those in the hands, foot and ankle ganglions are often associated with the underlying joints and tendons in these weight-bearing areas.
Uncommon Sites of Ganglion Cysts
While ganglion cysts are predominantly found in the wrists, hands, ankles, and feet, they can occasionally occur in less common locations throughout the body. These rarer presentations are still benign, but their presence in unusual sites may sometimes lead to different symptoms. For instance, ganglion cysts can develop around the knee.
Ganglion cysts may also be found in the shoulder joint. These typically arise from the joint capsule or surrounding structures and can cause pain or limited function if they grow large enough to compress nerves or other tissues. In some instances, cysts can even form within the spine, known as spinal ganglion cysts, which can sometimes press on nerves, leading to pain or weakness. Their appearance in these areas is infrequent compared to the extremities.
Understanding Cyst Formation
Ganglion cysts are believed to form as an outpouching or distension of a weakened portion of a joint capsule or tendon sheath. Joints and tendons are surrounded by a tissue called the synovial membrane, which produces a thick, lubricating fluid known as synovial fluid. This fluid helps the joints and tendons move smoothly. When there is irritation, degeneration, or repetitive stress to the joint or tendon, the synovial membrane can herniate or bulge outward.
This herniation creates a sac-like structure that fills with the thick, jelly-like fluid. The fluid within the cyst is similar in composition to synovial fluid but is often more viscous. Some theories suggest that a one-way valve mechanism allows fluid to exit the joint or tendon sheath and collect in the cyst, but not easily flow back, causing the cyst to enlarge. The exact triggers for this process are not fully understood, but factors like microtrauma or underlying joint degeneration are thought to contribute.
Next Steps After Discovery
Upon discovering a lump that might be a ganglion cyst, seeking professional medical evaluation is important. A healthcare provider can accurately diagnose the lump, often through physical examination, and rule out other conditions. Imaging tests like X-rays, ultrasound, or MRI may be used to confirm the diagnosis, assess the cyst’s size and connection to surrounding structures, or exclude other potential issues.
Many ganglion cysts are painless and do not require immediate treatment, often resolving on their own over time. If the cyst causes pain, interferes with movement, or is a cosmetic concern, several management options are available. Initial approaches may include observation, immobilization with a brace or splint to reduce activity and pressure, or over-the-counter pain medication.
If symptoms persist, a provider might perform an aspiration, which involves draining the fluid from the cyst with a needle. However, cysts can recur after aspiration because the connection to the joint or tendon sheath remains. Surgical removal, which excises the entire cyst and its origin, is an option for persistent or problematic cysts, though recurrence is still possible even after surgery.