Lateral epicondylitis, or 'tennis elbow', is a common condition that usually affects patients between 35 and 55 years of age. It is generally self-limiting, but in some patients it may continue to cause persistent symptoms, which can be refractory to treatment.
In conclusion, lateral epicondylitis is generally a self-limiting condition with a natural history of between ten and 18 months. In the vast majority of patients the condition will eventually resolve, and symptoms are usually adequately controlled by activity modification, physiotherapy and non-operative measures.
Lateral epicondylitis was first described in the medical literature by Runge in 1873. Rather than an inflammatory condition, it is a tendinosis (i.e., chronic symptomatic degeneration of the tendon) that affects the common attachment of the tendons of the extensor muscles of the forearm (extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi and extensor carpi ulnaris) to the lateral epicondyle of the humerus.
In the United Kingdom it affects between 1% and 3% of the population, mainly those aged from 35 to 55 years, with an equal gender distribution. It is generally self limiting, and most cases require no more than treatment with simple analgesia.
In most cases of lateral epicondylitis no obvious underlying cause can be identified. However, any activity that involves overuse of the wrist extensor or supinator muscles may be incriminated. The most commonly affected muscle is the extensor carpi radialis brevis (ECRB).
Although popularly associated with tennis, lateral epicondylitis may develop from a variety of activities that involve excessive and repetitive use of the forearm extensors, such as typing, playing the piano and various types of manual work. When affected, any movement that puts force on the extended wrist may be painful, as it increases the load on the diseased common extensor tendon.
Lateral epicondylitis was previously considered to be a tendinitis, arising as inflammation of the tendon. However, it has been shown histopathologically to have a paucity of inflammatory cells such as macrophages and neutrophils. The condition is therefore now considered to be a tendinosis, which is defined as a degenerative process.
Tendons have a limited blood supply when compared with muscle, and are susceptible to injury when muscles remain contracted for long periods, effectively rendering the tendon avascular. This leads to the generation of destructive free radicals on reperfusion. Tendons undergoing repetitive use may experience a rise in temperature of up to 10%, which can lead to hyperthermic injuries. Another theory is that injury to the tendon activates protein kinases, which lead to apoptosis.
Although it is known that the structure of the affected tendon in lateral epicondylitis is degenerate with multiple micro-tears, in itself that is not sufficient to explain the variability in patients’ symptoms. The cause of pain in lateral epicondylitis is thought to be due in part to an increased concentration of neurotransmitters such as glutamate, which sensitise the pain response, and to direct irritation from chemicals such as lactate, which have been found to be increased in tendinopathy.
Patients most often complain of pain at or around the bony prominence of the lateral epicondyle that often radiates down the forearm in line with the common extensor muscle mass and occasionally proximally into the upper arm. This pain is usually triggered or exacerbated by contraction of the common extensor mass in response to a variety of activities. The intensity of the pain can range from intermittent and mild to constant and severe, affecting all daily activities, and even occur at night causing a disturbance in sleep.
Examination is unlikely to reveal obvious abnormalities on inspection alone. In patients with longstanding disease or who have had previous corticosteroid injections, there may be prominence of the bony epicondyle as a result of muscle wasting or of partial or complete rupture of the extensor tendon at its attachment. In addition there may be depigmentation or thinning of the overlying skin as a result of corticosteroid injection.
Tenderness is typically found on palpation at the site of insertion of the ECRB tendon, which is just anterior to the anterior border of the lateral epicondyle. However, not uncommonly the tenderness is more diffuse, centred around the lateral epicondyle, with a point of tenderness at the bony prominence itself.
Usually a full range of active and passive movement is maintained at the elbow with, in more severe cases, pain at the limit of elbow extension when the forearm is fully pronated.
Accurate diagnosis of lateral epicondylitis may be difficult as there are a number of other conditions with similar clinical features. Conditions that can mimic lateral epicondylitis include:
Plain elbow radiographs can be helpful to exclude bony pathologies, including loose bodies, osteoarthritis and osteochondritis dissecans. In some cases patchy calcification in the overlying soft tissue may be seen on plain radiographs at the attachment of the common extensor tendon.
Ultrasound imaging can be useful by identifying structural changes in the affected tendons, including thickening or thinning, hypoechogenic foci indicating intra-substance degenerative areas, tendon tears, calcification, bony irregularity or calcific deposits. Doppler ultrasound is able to detect neovascularisation. The absence of this and of grey-scale changes have been shown to rule out lateral epicondylitis.
MRI can demonstrate other intra-articular pathology, confirm the presence of degenerative tissue and tears within the tendon and underlying capsule.
The aims of treatment for lateral epicondylitis include:
Rest, avoidance of aggravating activities and modification of behaviour usually lead to a remission in symptoms.
Physiotherapy can help in reducing pain in patients with lateral epicondylitis by focusing on maintaining range of movement, as well as eccentric strengthening exercises. Rehabilitation of the elbow requires proximal stability at the shoulder. This is achieved by strengthening and stabilising the scapula. The focus should initially be on the lower trapezius and serratus anterior muscles, beginning with simple open chain exercises followed by closed chain exercises, which will then also recruit the rotator cuff muscles.
Acupuncture has been shown to have short-term clinical benefits. However, the long-term benefits are still unclear.
Non-steroidal anti-inflammatory drugs (NSAIDs) may improve short-term function.
A study has shown that topical nitrates are effective in the reduction of pain in lateral epicondylitis. The nitrates are thought to stimulate collagen production through an increase in local blood flow and so promoting healing of the ECRB tendon.
Local injection of corticosteroids is a commonly used treatment in management of tennis elbow. The exact mechanism of action in a tendinopathic condition such as lateral epicondylitis is poorly understood, as the effects of corticosteroid are predominantly anti-inflammatory. Corticosteroids have been found to be superior to NSAIDs at four weeks, but no long-term differences were noted between steroid injections and NSAID treatment.
Injections may be administered using a single-injection technique or peppered injections into multiple areas of the tendon. This is thought to stimulate local blood flow. A randomized trial compared single versus peppered injections of corticosteroids and found slightly better improvements in the peppered injection group in terms of Disabilities of the Arm, Shoulder and Hand (DASH) score, visual analogue scale (VAS) for pain and grip strength. However, corticosteroids have been associated with local skin atrophy, depigmentation and muscle wasting, resulting in an increase in the bony prominence of the lateral epicondyle.
Botulinum toxin affects the neuromuscular junction by reducing resting muscle tone. By effectively reducing the resting tension at the ECRB insertion it may potentially reduce pain. At present there is no consensus on the use of botulinum toxin in lateral epicondylitis.
Platelet-rich plasma (PRP) is a concentrate of platelets derived from the patient’s own blood and is known to contain a high content of growth factors that have the potential to enhance the healing process of the tendon. A blood sample is taken and centrifuged to extract the plasma content, and the blood is then re-injected around the lateral epicondyle. A number of RCTs have shown that PRP is superior to autologous blood and bupivacaine injections. However there is a great variation in the way that different commercial systems prepare and activate the PRP, and hence it is difficult to draw clear conclusions on the efficacy of PRP.