The distal musculotendinous unit of the triceps muscle is subjected to an amazing variation of stresses as it performs its function to allow range of motion of the elbow, while at the same time providing elbow stability. The relatively poor blood supply of the distal musculotendinous unit limits the ability of the muscle and tendon to heal when traumatized. Over time, muscle tears and tendinopathy develop, further weakening the musculotendinous unit and making it susceptible to additional damage.

The triceps tendon of the elbow may develop tendonitis after overuse or misuse, especially when performing activities that require repeated flexion and extension of the elbow. Acute triceps tendonitis has been seen in clinical practice with increasing frequency due to the popularity of workouts utilizing exercise machines. Improper stretching of triceps muscle and triceps tendon before exercise has also been implicated in the development of triceps tendonitis as well as acute tendon rupture. Injuries ranging from partial to complete tears of the tendon can occur when the distal tendon sustains direct trauma while it is fully flexed under load or when the elbow is forcibly flexed while the arm is fully extended (Fig. 59.1).

The pain of triceps tendonitis is constant and severe and is localized to the posterior elbow region. The patient suffering from triceps tendonitis often complains of sleep disturbance and is unable to sleep on the affected elbow. Patients with triceps tendonitis exhibit pain with active resisted extension of the elbow. In an effort to decrease pain, patients suffering from triceps tendonitis often splint the inflamed tendon by limiting forearm extension to remove tension from the inflamed tendon. If untreated, patients suffering from triceps tendonitis may experience difficulty in performing any task that requires flexion and extension of the forearm. Over time, if the tendonitis is not treated, muscle atrophy and calcific tendonitis may result, or the muscle may suddenly rupture. Patients who experience complete rupture of the triceps tendon will not be able to fully and forcefully extend the affected arm (Fig. 59.2).

Plain radiographs are indicated in all patients who present with elbow pain (Fig. 59.3). 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 elbow is indicated if triceps tendinopathy or tear is suspected (Fig. 59.4). Magnetic resonance imaging or ultrasound evaluation of the affected area may also help delineate the presence of calcific tendonitis or other elbow pathology.

The triceps brachii muscle is a three-headed muscle that serves as the main extensor of the elbow joint and is the antagonist muscle to the biceps brachii and brachialis muscles (Fig. 59.5). Each of the three heads of the triceps muscle has a different origin. The long head of the triceps finds its origin at the infraglenoid fossa of the scapula and received innervation from the axillary nerve, unlike the rest of the triceps, which is innervated by the radial nerve. The medial head finds its origin at the groove of the radial nerve as well as from the dorsal surface of the humerus, the medial intermuscular septum, and the lateral intermuscular septum. The lateral head finds its origin at the dorsal surface of the humerus at a point lateral and proximal to the grove of the radial nerve as well as the greater tubercle down to the region of the lateral intermuscular septum. The three heads of the triceps muscle coalesce into the dense distal triceps tendon, which inserts onto the olecranon process and the posterior wall of the capsule of the elbow joint (Fig. 59.6). It is at its point of insertion that the distal triceps musculotendinous unit is susceptible to the development of tendonitis, tears, and rupture.