Tennis elbow, which is also known as lateral epicondylitis, is a painful condition of the upper extremity that is caused by repetitive overuse or misuse of the extensor tendons of the forearm. Over time, microscopic tears begin to occur at the origin of the musculotendinous units of the extensor carpi radialis brevis and extensor carpi ulnaris muscles (Fig. 56.1). The repetitive process of tearing and healing of the musculotendinous units of the extensor tendons sets up an inflammatory process that ultimately results in pain and functional disability. If not properly treated, complete rupture of the tendinous insertion of these extensor muscles can occur (Fig. 56.2). It has been postulated that a combination of the poor blood supply of the extensor tendons combined with the significant concentric and eccentric stresses placed on these tendons may be responsible for the evolution of this common pain syndrome.

Activities that require increased grip pressure and high torque twisting of the wrist have been implicated in the evolution of tennis elbow. The biomechanics responsible for the development of tennis elbow in players of racquet sports include the (1) use of an increased grip strength to support a racquet that is too long or too heavy for the player and (2) making backhand shots with a leading shoulder and elbow rather than keeping the shoulder and elbow parallel to the net (Fig. 56.3).

The signs and symptoms frequently observed in patients suffering from tennis elbow include pain that is localized to the lateral epicondyle with maximal point tenderness at the site of the insertion of the musculotendinous units of the extensor carpi radialis brevis and extensor carpi ulnaris muscles. The pain is constant in nature with the patient experiencing an acute exacerbation of pain with any activity that requires gripping with the hand, extending the wrist, or supinating the forearm. The patient suffering from tennis elbow may complain of significant sleep disturbance with awakening when the patient rolls over onto the affected elbow. On physical examination, there is exquisite point tenderness to palpation at or just below the lateral epicondyle. Careful palpation of the area may reveal a band-like thickening of the extensor tendons, and color may be noted. Grip strength is often diminished, and patients will exhibit a positive tennis elbow test. The tennis elbow test is performed by stabilizing the patient’s forearm and then having the patient clench his or her fist and actively extend the wrist (Fig. 56.4). The examiner then attempts to force the wrist into flexion. Sudden, severe pain is highly suggestive of tennis elbow.

Tennis elbow can be confused with radial tunnel syndrome as well as a C6 to C7 radiculopathy. Tennis elbow can be distinguished from radial tunnel syndrome by determining the site of maximal tenderness to palpation. Patients suffering from tennis elbow will experience maximal tenderness to palpation over the lateral epicondyle, whereas patients suffering from radial tunnel syndrome will experience maximal tenderness to palpation distal to the lateral epicondyle over the radial nerve (Fig. 56.5).

Furthermore, it should be remembered that cervical radiculopathy and ulnar nerve entrapment may coexist as the socalled double crush syndrome. The double crush syndrome is seen most commonly with median nerve entrapment at the wrist or with carpal tunnel syndrome but has been reported with the radial nerve.

Electromyography and nerve conduction velocity testing are useful in helping in the differentiation of tennis elbow from cervical radiculopathy and radial tunnel syndrome. Plain radiographs, ultrasound imaging, and magnetic resonance imaging are indicated in all patients who are thought to be suffering from tennis elbow in order to confirm the diagnosis as well as to rule out occult bony pathology involving the lateral epicondyle and elbow joint and to identify occult fractures, masses, or tumors that may be responsible for the patient’s symptomatology (Figs. 56.6 and 56.7). Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood count, uric acid, sedimentation rate, and antinuclear antibody testing. The ultrasound-guided injection technique described below serves as both a diagnostic and therapeutic maneuver as ultrasound imaging can clearly delineate pathology of the extensor musculotendinous units at their insertion on the lateral epicondyle. This technique can also be used to guide percutaneous tenotomy (Fig. 56.8).

The key landmarks when performing ultrasound-guided tennis elbow are the extensor tendons of the extensor carpi radialis brevis and extensor carpi ulnaris muscles and their point of origin on anterior facet of the lateral epicondyle of the elbow. The extensor radialis longus musculotendinous unit may also be affected at its origin at the supracondylar crest of the humerus. Confusion in the clinical presentation of cubital and olecranon bursitis may coexist with tennis elbow. The radial
nerve passes into the substance of the brachioradialis muscle, and at a point just above the lateral epicondyle, the radial nerve divides into deep and superficial branches; the superficial branch continues down the arm along with the radial artery to provide sensory innervation to the dorsum of the wrist and the dorsal aspects of a portion of the thumb and index and middle fingers, and the deep branch provides the majority of the motor innervation to the extensors of the forearm.