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What is Tennis elbow and explain in detail?
Tennis elbow, also known as lateral epicondylitis or enthesopathy of the extensor carpi radialis origin, is a condition in which the outer part of the elbow becomes painful and tender. The pain may also extend into the back of the forearm. Onset of symptoms is generally gradual although they can seem sudden and be misinterpreted as an injury. Golfers elbow is a similar condition that affects the inside of the elbow.Enthesopathies are idiopathic, meaning science has not yet determined the cause. Enthesopathies are most common in middle age (ages 35 to 60).It is often stated that the condition is caused by excessive use of the muscles of the back of the forearm, but this is not supported by experimental evidence and is a common misinterpretation or unhelpful thought about symptoms. It may be associated with work or sports, classically racquet 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 particularly useful. Signs consistent with the diagnosis include pain when a subject tries to bend back the wrist when the wrist is against resistance.Treatment involves decreasing activities that bring on the symptoms together with physical therapy or other treatment gradually increasing loads. Pain medications such as NSAIDS or acetaminophen (paracetamol) may be used. A brace over the upper forearm may also be helpful. The role of corticosteroid injections is debated.

Signs and symptoms
Pain on the outer part of the elbow (lateral epicondyle)
Point tenderness over the lateral epicondyle—a prominent part of the bone on the outside of the elbow
Pain with resisted wrist extension or passive wrist flexionSymptoms associated with tennis elbow include, but are not limited to, pain from the outside of the elbow to the forearm and wrist and pain during extension of wrist.

Terminology
The term "tennis elbow" is widely used (although informal), but the condition should be understood as not limited to tennis players.  Historically, the medical term "lateral epicondylitis" was most commonly used for the condition, but "itis" implies inflammation and the condition is not inflammatory.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
Enthesopathy of the extensor carpi radialis brevis origin is idiopathic, meaning that it has no known cause.Tennis players generally believe tennis elbow is caused by the repetitive nature of hitting thousands of tennis balls, which leads to tiny tears in the forearm tendon attachment at the elbow. 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 on histopathology, and misinterpretation of painful activities as a source of damage is common.

Early experiments suggested that tennis elbow was primarily caused by overexertion. However, studies show that trauma such as direct blows to the epicondyle, a sudden forceful pull, or forceful extension cause more than half of these injuries. Repeatedly mis-hitting a tennis ball in the early stages of learning the sport causes shock to the elbow joint and may contribute to contracting the condition.

Pathophysiology
Histological findings include granulation tissue, micro-rupture, degenerative changes, and there is no traditional inflammation. Therefore, the disorder is more appropriately referred to as tendinosis or tendinopathy—more accurately an enthesopathy—rather than tendinitis. There is no evidence of inflammation or repair.The extensor digiti minimi also has a small origin site medial to the elbow that this condition can affect. The muscle involves the extension of the little finger and some extension of the wrist allowing for adaption to "snap" or flick the wrist—usually associated with a racquet swing. Most often, the extensor muscles become painful due to tendon breakdown from over-extension.  Improper form or movement allows for power in a swing to rotate through and around the wrist—creating a moment on that joint instead of the elbow joint or rotator cuff. This moment causes pressure to build impact forces to act on the tendon causing irritation and inflammation.Other speculative risk factors for lateral epicondylitis include taking up tennis later in life, unaccustomed strenuous activity, decreased mental chronometry and speed and repetitive eccentric contraction of muscle (controlled lengthening of a muscle group).

Diagnosis
Physical examination
Diagnosis is based on symptoms and clinical signs that are discrete and characteristic. For example, extension of the elbow and flexion of the wrist cause outer elbow pain. There is point tenderness at the origin of the extensor carpi radialis brevis muscle from the lateral epicondyle (extensor carpi radialis brevis origin), 1 cm distal and slightly anterior to the lateral epicondyle.  There is also pain with resisted wrist extension (Cozens test).

Medical imaging
Medical imaging is not necessary or helpful.X-rays can confirm and distinguish possibilities of existing causes of pain that are unrelated to tennis elbow, such as fracture or arthritis. Rarely, calcification can be found where the extensor muscles attach to the lateral epicondyle. Medical ultrasonography and magnetic resonance imaging (MRI) are other valuable tools for diagnosis but are frequently avoided due to the high cost.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.

Treatment
In some cases, severity of tennis elbow symptoms mend without any treatment, within six to 24 months. Tennis elbow left untreated can lead to chronic pain that degrades quality of daily living.

Physical therapy
There are several recommendations regarding prevention, treatment, and avoidance of recurrence that are largely speculative including stretches and progressive strengthening exercises to prevent re-irritation of the tendon and other exercise measures.One way to help treat minor cases of tennis elbow is simply to relax the affected arm. The rest lets stress and tightness within the forearm slowly relax and eventually have the arm in working condition—in a day or two, depending on the case.Other approaches that are not experimentally tested include eccentric exercise using a rubber bar. The exercise involves grasping a rubber bar, twisting it, then slowly untwisting it. Although it can be considered an evidence-based practice, long-term results have not yet been determined.There are differences in opinions on whether it is okay if pain occurs during these exercises. Some suggest pain of less than 5/10 is okay.Moderate evidence exists demonstrating that joint manipulation directed at the elbow and wrist and spinal manipulation directed at the cervical and thoracic spinal regions results in clinical changes to pain and function. There is also moderate evidence for short-term and mid-term effectiveness of cervical and thoracic spine manipulation as an add-on therapy to concentric and eccentric stretching plus mobilisation of wrist and forearm. Although not yet conclusive, the short-term analgesic effect of manipulation techniques may allow more vigorous stretching and strengthening exercises, resulting in a better and faster recovery process of the affected tendon in lateral epicondylitis.Low level laser therapy, administered at specific doses and wavelengths directly to the lateral elbow tendon insertions, may result in short-term pain relief and less disability.Extracorporeal shockwave therapy, while safe, is of unclear benefit.

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. This position reduces the overloading strain at the lesion area.

Medication
Although anti-inflammatories are a commonly prescribed treatment for tennis elbow, the evidence for their effect is usually anecdotal with only limited studies showing a benefit. A systematic review found that topical non-steroidal anti-inflammatory drugs (NSAIDs) may improve pain in the short term (up to 4 weeks) but was unable to draw firm conclusions due to methodological issues. Evidence for oral NSAIDs is mixed.Evidence is poor for long term improvement from injections of any type, whether corticosteroids, botulinum toxin, prolotherapy or other substances. Corticosteroid injection may be effective in the short term however are of little benefit after a year, compared to a wait-and-see approach. A randomized control trial comparing the effect of corticosteroid injection, physiotherapy, or a combination of corticosteroid injection and physiotherapy found that patients treated with corticosteroid injection versus placebo had lower complete recovery or improvement at 1 year (Relative risk 0.86). Patients that received corticosteroid injection also had a higher recurrence rate at 1 year versus placebo (54% versus 12%, relative risk 0.23).
Complications from repeated steroid injections include skin problems such as hypopigmentation and fat atrophy leading to indentation of the skin around the injection site. Steroid injections against appear to be more effective than shock wave therapy. Botulinum toxin type A to paralyze the forearm extensor muscles in those with chronic tennis elbow that has not improved with conservative measures may be viable.

Surgery
Surgery is an option. Surgical methods include:
Lengthening, release, debridement, or repair of the origin of the extrinsic extensor muscles of the hand at the lateral epicondyleSurgical techniques for lateral epicondylitis can be done by open surgery, percutaneous surgery or arthroscopic surgery, with no high-quality evidence that any particular type is better or worse than another. Side effects include infection, damage to nerves and inability to straighten the arm.  A review of the evidence related to surgery found that published studies were of low quality and did not show that surgery was any more effective than other treatments.  A subsequent research trial showed that surgery was no more effective than sham surgery, where patients only received a skin incision, although the trial was limited by a small number of patients.

Prognosis
Response to initial therapy is common, but so is relapse (25% to 50%) and/or prolonged, moderate discomfort (40%).Depending upon severity and quantity of multiple tendon injuries that have built up, the extensor carpi radialis brevis may not be fully healed by conservative treatment.  Nirschl defines four stages of lateral epicondylitis, showing the introduction of permanent damage beginning at Stage 2.

Inflammatory changes that are reversible
Nonreversible pathologic changes to origin of the extensor carpi radialis brevis muscle
Rupture of ECRB muscle origin
Secondary changes such as fibrosis or calcification.

Epidemiology
In tennis players, about 39.7% have reported current or previous problems with their elbow. Less than one quarter (24%) of these athletes under the age of 50 reported that the tennis elbow symptoms were "severe" and "disabling," while 42% over the age of 50 did. More women (36%) than men (24%) considered their symptoms severe and disabling.  Tennis elbow is more prevalent in individuals over 40, where there is about a four-fold increase among men and two-fold increase among women.  Tennis elbow equally affects both sexes and, although men have a marginally higher overall prevalence rate as compared to women, this is not consistent within each age group, nor is it a statistically significant difference.Playing time is a significant factor in tennis elbow occurrence, with increased incidence with increased playing time being greater for respondents under 40. Individuals over 40 who played over two hours doubled their chance of injury. Those under 40 increased it 3.5 fold compared to those who played less than two hours per day.

History
German physician F. Runge is usually credited for the first description of the condition, calling it "writers cramp" (Schreibekrampf) in 1873.  Later, it was called "washer womens elbow"