Condition in which the outer part of the elbow becomes sore and tender
Medical condition
Tennis elbow, also known as lateral epicondylitis is an enthesopathy (attachment point disease) of the origin of the extensor carpi radialis brevis on the lateral epicondyle.  It causes pain and tenderness over the bony part of the lateral epicondyle. Symptoms range from mild tenderness to severe, persistent pain. The pain may also extend into the back of the forearm. It usually has a gradual onset, but it can seem sudden and be misinterpreted as an injury.
Tennis elbow is often idiopathic. Its cause and pathogenesis are unknown. It likely involves tendinosis, a degeneration of the local tendon.
It is thought this condition is caused by excessive use of the muscles of the back of the forearm, but this is not supported by evidence. It may be associated with work or sports, classically racquet sports (including paddle sports), but most people with the condition are not exposed to these activities. The diagnosis is based on the symptoms and examination. Medical imaging is not very useful.
Untreated enthesopathy usually resolves in 1–2 years. Treating the symptoms and pain involves medications such as NSAIDS or acetaminophen, a wrist brace, or a strap over the upper forearm. The role of corticosteroid injections as a form of treatment is still debated. Recent studies suggests that corticosteroid injections may delay symptom resolution.
Signs and symptoms.
Patients typically feel pain or burning around the outer part of the elbow (lateral epicondyle of the humerus), which can move down the forearm and sometimes up to the upper arm. The pain is worsened by activities that involve wrist extension, such as gripping objects. Pain intensity varies from mild to severe and can be intermittent or constant, significantly impacting daily life. Patients also commonly report grip weakness and difficulty lifting.
Terminology.
The term "tennis elbow" is widely used (although informal), but the condition affects non-tennis players. More recently, with the explosive growth of pickleball, the term "pickleball elbow" is frequently used. Historically, the medical term "lateral epicondylitis" was most commonly used for the condition, but "itis" implies inflammation and the condition is not inflammatory. It is also referred to as enthesopathy of the extensor carpi radialis origin.
Since histological findings reveal noninflammatory tissue, the terms "lateral elbow tendinopathy" and "tendinosis" are suggested. In 2019, a group of international experts suggested that "lateral elbow tendinopathy" was the most appropriate terminology. But a disease of an attachment point (or enthesia) is most accurately referred to as an "enthesopathy."
Causes.
The exact cause of lateral epicondylitis remains unclear. However, it is often linked to repetitive microtrauma resulting from excessive gripping, wrist extension, radial deviation, and/or forearm supination.
Traditionally, people have speculated that tennis elbow is a type of repetitive strain injury resulting from tendon overuse and failed healing of the tendon, but there is no evidence of injury or repair, and misinterpretation of painful activities as a source of damage is common.
Pathophysiology.
The extensor carpi radialis brevis is the most commonly affected muscle in lateral epicondylitis (LE), along with other extensor carpal muscles. Due to its unique origin, the ECRB tendon is prone to abrasion during elbow movements, leading to repetitive microtrauma.
Lateral epicondylitis was initially considered an inflammatory process, however there is no evidence of inflammation or repair. Therefore, the disorder is more appropriately referred to as "tendinosis" or "tendinopopathy." Tendinosis, a degenerative condition with fibroblasts, abnormal collagen, and increased blood vessels. Repetitive stress causes microtears, scar tissue formation, and biomechanical changes, worsening symptoms over time.
Recently, successful results of a prospective therapeutic study of tennis elbow were published. It was observed that tennis elbow symptoms were most painful after awakening. It was hypothesized that a very common sleep position was interfering with healing and causing pain. The study evaluated if changing this position would avoid pressure on the lateral elbow while asleep. Patients who changed this sleep position reported successful resolution of symptoms, whereas those who were unable to change continued to have pain. The conclusion reached is that the pathophysiology of tennis elbow is due to an initial microscopic tear from a sprain/strain. This initial injury is aggravated at night by pressure on the sprain which delays healing. In other words, tennis elbow is neither a tendonitis nor a tendinosis, but more like a pressure sore. If the pressure is removed the initial injury goes on to heal. The importance of this finding is that other conditions characterized by nocturnal or early morning symptoms may also be worsened by a “pathological sleep position.” We know this applies to carpal and cubital tunnel syndrome, plantar fasciitis, shoulder/neck pain and Gerd. 
Clinical evaluation.
Physical examination.
Diagnosis is based on symptoms and clinical signs that are discrete and characteristic. For example, the extension of the elbow and flexion of the wrist causes outer elbow pain. The physical examination usually reveals marked tenderness at the origin of the extensor carpi radialis brevis muscle from the lateral epicondyle (extensor carpi radialis brevis origin). Pain may worsen with resisted wrist extension, middle finger extension, and forearm supination with an extended elbow, although normal elbow movement is often maintained, even in severe cases.
Cozen's test.
Cozen's test is a physical examination performed to evaluate for tennis elbow involving pain with resisted wrist extension. The test is said to be positive if a resisted wrist extension triggers pain to the lateral aspect of the elbow owing to stress placed upon the tendon of the extensor carpi radialis brevis muscle. The test is performed with extended elbow. NOTE: With elbow flexed the extensor carpi radialis longus is in a shortened position as its origin is the lateral supracondylar ridge of the humerus. To rule out the ECRB (extensor carpi radialis brevis), repeat the test with the elbow in full extension.
Medical imaging.
Medical imaging is not necessary or helpful.
Radiographs (X-rays) may demonstrate calcification where the extensor muscles attach to the lateral epicondyle. Medical ultrasonography and magnetic resonance imaging (MRI) can demonstrate the pathology, but are not helpful for diagnosis and do not influence treatment.
Longitudinal sonogram of the lateral elbow displays thickening and heterogeneity of the common extensor tendon that is consistent with tendinosis, as the ultrasound reveals calcifications, intrasubstance tears, and marked irregularity of the lateral epicondyle. Although the term “epicondylitis” is frequently used to describe this disorder, most histopathologic findings of studies have displayed no evidence of an acute, or a chronic inflammatory process. Histologic studies have demonstrated that this condition is the result of tendon degeneration, which replaces normal tissue with a disorganized arrangement of collagen. Colour Doppler ultrasound reveals structural tendon changes, with vascularity and hypo-echoic areas that correspond to the areas of pain in the extensor origin.
Table of Clinical classification of lateral epicondylitis phases.
Prevention.
Activity modification is the best way to prevent the occurrence of lateral epicondylitis. Prevention can include avoiding extreme end range motions in extension and flexion, limit repetitive hand and wrist motions, and modification of heavy lifting with extended arms. Lifestyle factors such as smoking, alcohol drinking, and dietary habits are known to influence the prognosis of various medical conditions. Smokers showed a higher chance of developing lateral epicondylitis compared to non-smokers. Current research indicates that alcohol intake is not significantly associated with lateral epicondylitis.
Treatment.
Non-Operative Treatment.
Non operative treatment resolves 90% of symptomatic lateral epicondylitis. Nonoperative care usually includes activity modification, physical therapy, non-steroidal anti-inflammatory medications, bracing, extracorporeal shock-wave therapy, and acupuncture. Modifying activity and avoiding overuse are key to treatment. Lifting with the palm up and avoiding palm-down movements can shift strain from the lateral to the medial epicondyle, easing pain. Patients should also improve lifestyle habits and avoid triggering activities. Following the RICE method (rest, ice, compression, elevation) can help relieve pain initially.
Exercises.
Stretching and isometric strengthening are the most common recommended exercises. 
The muscle is stretched with the elbow straight and the wrist passively flexed. 
Isometric strengthening can be done by pushing the top of the hand up against the undersurface of a table and holding the wrist straight.
Orthotic devices.
Orthosis is a device externally used on the limb to improve the function or reduce the pain. Orthotics may be useful in tennis elbow; however, long-term effects are unknown. There are two main types of orthoses prescribed for this problem: counterforce elbow orthoses and wrist extension orthoses. Counterforce orthosis has a circumferential structure surrounding the arm. This orthosis usually has a strap which applies a binding force over the origin of the wrist extensors. The applied force by orthosis reduces the elongation within the musculotendinous fibers. Wrist extensor orthosis maintains the wrist in the slight extension.
Speculative treatments.
Other approaches that are not experimentally tested include eccentric exercise using a rubber bar, joint manipulation directed at the elbow and wrist, spinal manipulation directed at the cervical and thoracic spinal regions, low level laser therapy, and extracorporeal shockwave therapy.
Medication.
Recent studies demonstrate that topical nonsteroidal anti-inflammatory medications are effective within four weeks for lateral epicondylitis. Evidence for oral NSAIDs is mixed. Research indicates that  corticosteroid injections improved outcomes more effectively than NSAIDs within four weeks but offered no long-term benefits at 12 months.
Other studies suggest that, while helpful for short-term pain relief, corticosteroid injections are less effective than watchful waiting or physical therapy after one year. Repeated injections can also lead to tendon rupture and muscle atrophy. Thus, clinicians should be cautious with corticosteroid use for lateral epicondylitis due to limited long-term effectiveness and possible adverse effects.
Alternative Treatments.
While many alternative treatments, such as shockwave, laser, low-frequency electrical nerve stimulation, ultrasound, and pulsed magnetic wave therapies, have been used, none have been proven effective. Current evidence is inconclusive on the effectiveness of acupuncture was effective for lateral epicondylitits.
Platelet-Rich Plasma (PRP) Injections.
Platelet-Rich Plasma (PRP) has emerged as a potential treatment for lateral epicondylitis. PRP is derived from the patient's own blood and contains concentrated platelets, which are rich in growth factors. These growth factors are believed to initiate and accelerate tissue repair and regeneration support healing of the tendons and connective tissue and promote the growth of new blood vessels, aiding the recovery process.
The PRP procedure for lateral epicondylitis involves extracting a small amount of the patient's blood, separating the plasma through centrifugation, and re-injecting it directly into the lateral epicondyle. While good outcomes have been reported with PRP for lateral epicondylitis, the overall literature is still unclear on its effectiveness. Additionally, variations in PRP preparation methods and injection techniques across different commercial systems add further complexity to assessing its effectiveness.
Overall, current research on PRP as a treatment for lateral epicondylitis is promising. However, more studies are needed to provide clear evidence of its effectiveness.
Surgery.
Most patients with lateral epicondylitis (tennis elbow) improve with conservative treatments and do not need surgery. However, if symptoms persist despite prolonged conservative therapy, surgical options should be reconsidered. Several surgical procedures are available for lateral epicondylitis, most involving the removal of damaged tissue from the ECRB and scraping of the lateral epicondyle. This procedure can be done through open, percutaneous, or arthroscopic methods.
Percutaneous Surgery.
Percutaneous surgical approach is mainly used for releasing the common extensor tendon origin at the lateral epicondyle. This technique has been demonstrated to be safe, reliable, and cost-effective Good midterm outcomes in pain relief have been widely reported with a percutaneous surgical approach. However there is some limited evidence reported that arthroscopic and open techniques achieved a better prognosis than the percutaneous surgical approach for the treatment of lateral epicondylitis. In recent years, a new technique termed as ultrasound-guided percutaneous tenotomy has been reported as a safe and effective for the treatment of lateral epicondylitis, with improvements in symptoms, function, and ultrasound imaging at 1-year follow-up.
Arthroscopic Surgery.
Arthroscopic surgery is a minimally invasive option for treating lateral epicondylitis. This technique fully visualizes the elbow joint, and leads to a quicker return to work. In the past, studies have shown good long term effects and fewer complications with arthroscopic surgery compared to open or percutaneous approaches. However, the literature is currently mixed with some recent reviews suggest no significant differences among open, arthroscopic, and percutaneous methods regarding recovery time, complication rates, or patient satisfaction. While others state that arthroscopic surgery may allow for a quicker return to work, suggesting a potential advantage in the early postoperative period. While results are generally positive, arthroscopic surgery carries risks of injury to the radial nerve and lateral ulnar collateral ligament.
Epidemiology.
Tennis Elbow is a commonly seen condition and has been reported to affect 1% to 3% of adults each year. The incidence of lateral