Lateral epicondylitis

Lateral epicondylitis, also known as “tennis elbow,” is an overuse syndrome of the common extensor tendon and predominantly affects the extensor carpi radialis brevis(ECRB) tendon.

Epidemiology

Lateral epicondylitis occurs with a frequency seven to ten times that of medial epicondylitis. As with medial epicondylitis it typically occurs in 4^th to 5^th decades of life. There is no recognised gender predilection.

Clinical presentation

Patients often present with lateral elbow pain, which is frequently exacerbated when they grasp objects during wrist extension with resistance. A history of tennis playing or similar racket sports is sometimes elicited, but the condition often results from other repetitive athletic or occupational activities, or without an identifiable cause.

Pathology

It is thought that repetitive stress and overuse lead to tendinosis involving the origin of the extensor tendons at the lateral elbow, with microtrauma and partial tearing that may progress to a full-thickness tendon tear. Alternatively, it may also result from direct trauma.

Radiographic features

MR imaging is the most widely used modality, although ultrasound may also be performed.

Plain radiograph

Up to 25 % of patients with lateral epicondylitis may have calcification within the soft tissue around the lateral epicondyle.

Ultrasound

Thickening of the common extensor tendon, associated with diffuse heterogeneity and areas of focal hypoechogenicity. There is often associated intra-tendon calcification and bony irregularity at the tendon insertion. The most common finding in a patient with lateral epicondylitis is focal areas of low echogenicity with a background of intrinsic tendinopathy.

MRI  

The hallmarks of tendinosis and tearing of the common extensor tendon on MRI are abnormal morphology and signal intensity, as follows ⁷:

• the best diagnostic clue for diagnosis of lateral epicondylitis is abnormal thickening and increased signal intensity within the common extensor origin from the lateral epicondyle 
• abnormal thickening & abnormal separation of the radial collateral ligaments and the extensor carpi radials brevis (ECRB) with granulation tissue
• the imaging findings of tendinosis must be correlated with clinical data of lateral epicondylitis because if the patient is asymptomatic in presence of these findings, the case may be attributed to subclinical diagnosis or early tendon degeneration.
• partial or even full thickness tear of the ECRB complicating tendinosis may be encountered in patient with lateral epicondylitis. It is manifested as fluid filled gap with or without loss of fiber continuity.
• peritendon edema and associated focal bone marrow edema at the site of tendon attachment to the humerus may simulate avulsion injury
• in chronic cases increased signal intensity of the nearby anconeus muscle may be seen
• associated radial nerve entrapment may occur in 5% of cases
• radial collateral ligament may also be disrupted

Treatment and prognosis

Autologous blood injection has been shown to more effective at long-term relief than corticosteroid injection, with 90% of patients in one study being pain-free at six months ⁵. Whole blood injection has been shown to be just as a effective as platelet rich plasma (PRP) injection and is also much less expensive ⁶. 

Surgery is often performed if there is no clinical response after 3 to 6 months of conservative treatment.

History and etymology

It was initially described by Morris as “lawn tennis elbow” in 1882 and now most commonly termed as Tennistennis elbow.

Differential diagnosis

For a clinical differential diagnosis of lateral elbow pain, consider:

• occult fracture
• osteochondritis dissecans of the capitellum
• lateral osteoarthrosis
• lateral ulnar collateral ligament (LUCL) instability
• radial tunnel syndrome