Painless palpable soft tissue abnormalities over joints are commonly encountered in clinical practice. The differential diagnosis can be difficult solely on clinical grounds as benign ganglion cysts that present in areas other than the wrist and the ankle or often misdiagnosed as solid tumors and solid tumors that appear over the wrist and ankle are often misdiagnosed as benign ganglion cysts. Such misdiagnosis can lead to disastrous consequences if a malignant solid tumor is erroneously diagnosed as a benign ganglion cyst (Fig. 72.1). Ultrasound imaging of painless palpable soft tissue masses provides the clinician with immediate help with the solid tumor versus cystic mass differential diagnosis, and its increasing clinical use represents a great advance in the treatment of these sometimes confusing soft tissue abnormalities (Fig. 72.2). Ultrasound also allows the differentiation of simple versus complex multiloculated ganglion cysts that may require more involved treatment (Fig. 72.3). Ultrasound guidance also allows identification of adjacent structures that may be traumatized during injections, drainage, or surgical treatment of otherwise benign ganglion cysts (Fig. 72.4).

Ganglion cysts are thought to be the result of a mechanical pressure phenomenon that results in herniation of synovialcontaining tissues from joint capsules, tendon sheaths, and other connective tissue structures such as the triangular fibrocartilage complex. As this ectopic connective tissue becomes chronically inflamed, its synovial components may begin producing increased amounts of synovial fluid, which can pool in cyst-like cavities overlying the tendons and joint space (Fig. 72.5). A one-way valve phenomenon may cause these cyst-like cavities to expand because the fluid cannot flow freely back into the synovial cavity. These cyst-like cavities can develop as simple thin-walled cysts or can become complex multiloculated structures that can be difficult to treat (see Figs. 72.2 and 72.3). Ganglion cysts can form anywhere where these structures exist with the dorsum of the wrist as the most common site of the development of ganglion cysts. Ganglion cysts may also occur on the volar aspect of the wrist.

Ganglion cysts tend to be painless soft tissue swellings, but extreme flexion and extension of the wrist can cause pain secondary to compression of adjacent structures (Fig. 72.6). Rest of the affected part and the application of local heat may provide some relief. If pain occurs, it tends to be constant and is characterized as aching and dull. It is often the unsightly nature of the ganglion cyst, rather than the pain, which causes the patient to seek medical attention. The ganglion is smooth to palpation and transilluminates with a penlight in contradistinction to solid tumors, which do not transilluminate. Palpation of the ganglion may increase the pain.

Plain radiographs are indicated in all patients who present with wrist and hand pain. Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging or ultrasound imaging of the wrist and hand is indicated to confirm that the palpable soft tissue mass is in fact a ganglion cyst and not a solid tumor that may be malignant (Fig. 72.7).

Ganglion cysts can occur almost anywhere in the body but most commonly develop on the dorsum of the wrist in the area overlying the extensor tendons or the various joint space. Statistically, there is a predilection for ganglion cyst development over the dorsal scapholunate interval (Fig. 72.8).