Runge first reported on a disorder that was linked to pain in the humeral lateral condylar region and trouble writing in 1873. Morris later coined the term "lawn tennis arm" for this condition in 1882.¹ It has been referred to by several different names, such as angiofibroblastic hyperplasia, lateral epicondylitis(LE), and tendinosis.  Trauma to the lateral elbow can occur, however it is usually considered an overuse injury.² Approximately 40% of people experience LE at some point in their life. In general population the prevalence of LE is 1-3%. In a population based study by Sanders et al, the annual incidence of tennis elbow was reported to be 4.5 per 1000 people.³

This condition is primarily a degenerative overuse process of the extensor carpi radialis brevis (ECRB) and the common extensor tendon. Aside from degenerative changes, the histological findings include granulation tissue, micro-rupture, an abundance of fibroblasts, vascular hyperplasia, unstructured collagen, and a notable lack of traditional inflammatory cells (macrophages, lymphocytes, neutrophils) within the tissue.²

The majority of the patients complain pain located just anterior to, or in, the bony surface of the upper half of the lateral epicondyle, usually radiating in line with the common extensor mass. The pain can vary from intermittent and low-grade to continuous and severe which may cause sleep disturbance. It is typically produced by wrist and finger extensor muscle contraction against resistance. ⁴

Stability of a joint depends upon congruency of articular surfaces, thickness of articular cartilage, orientation of fibers in ligaments, capsule and direction of muscular pull, which together facilitate free and controlled joint movements. The stability of the PRUJ (Proximal Radio Ulnar Joint) is excellent because the radial head is enclosed in a very strong osteoligamentous cavity, made of the radial notch of the ulna and the annular ligament, which is a very resistant ligament. The total range of pronation- supination is roughly 180°, but the motion must be measured from a reference position (0)-elbow flexed at right angle and hand included in a vertical plane, the thumb being directed upward. From this position, the pronation is 90°, rotating the palm downward and the thumb medially. In the inverse motion-supination, normally 90°the palm is directed upward and the thumb is directed laterally. Supination, is the most important movement because it cannot be compensated by the shoulder, whereas a lack of pronation can be replaced by its abduction.⁸

In an elliptical radial head, the orientation of the long axis is perpendicular to the radial notch with the forearm in neutral rotation. The “non-circular shape” radial head does not rotate precisely around a specific centre in full pronation and supination. With pronation the radial head translates anteriorly, placing the posterior annular ligament under tension while in supination the radial head translates posteriorly, placing the anterior portion of the annular ligament under tension. ⁶

The longitudinal axis of the forearm rotation runs from the center of radial head and capitellum proximally to the base of the styloid process of the distal ulna distally. Therefore, it is oblique to the longitudinal axes of both the radius and the ulna and rotation is independent of elbow position. The axis of rotation shifts slightly ulnar and volar in supination and radial and dorsal during pronation. The radius has been shown to move proximally by 1 to 2 mm with pronation.⁷

During pronation, radius crosses over ulna as a result its anterior concavity of sagittal plane now faces posteriorly. Flexor muscles which lie anterior to both bones during supination come and lie between them as “mattress” softening their contact, displacing ulna posteriorly with respect to radius. Also cupped radial head and cylindrical radial head rim rotate medially over humeral capitulum and in fibro- osseous ring respectively. Hence plane of proximal surface of radial head tilts dorsally, distally & laterally (as great axis of radial head comes to lie transversely so that long axis of radius displaces laterally by 2 mm). During supination cupped radial head and cylindrical radial head rim rotate laterally over humeral capitulum and in fibro-osseous ring respectively so that radius now lies parallel to ulna.

Hence plane of proximal surface of radial head tilts ventrally, proximally and medially altering tension

in annular ligament and therefore the lateral ligament complex which in turn reduces stress on common extensor origin.⁸

Forearm supination is performed by two main muscles, the biceps brachii and supinator muscles⁹ and forearm pronation is performed by pronator teres and pronator quadratus. Supinator is wrapped around the neck of radius whereas biceps are inserted into the apex of the “supinator bend” that is the radial tuberosity. The pronator quadratus is wrapped around the distal end of the ulna, so that the radius moves around the ulna whereas the pronator teres inserted into the apex of the “pronator bend” of the radius.⁸ At proximal radio ulnar joint transverse stability is mainly due to annular ligament and to a lesser extend, quadrate/squared ligament. Annular ligament, not like conventional ligaments inserts on anterior and posterior rims of radial notch of ulna, winds around radial head. Its inner aspect is lined with fibrocartilage that makes radial head easier to move during forearm rotation. Quadrate/squared ligament is present at inferior part, it tightens in pronation and supination by wrapping around radial neck, thereby drawing radial head closer to ulna hence, providing transverse stability and also longitudinal stability by limiting vertical migration of radius. In most cases, the lesion will involve the junctional tissue at the common extensor muscle origin of the lateral epicondyle, specifically, the ECRB. If the ECRB is involved, extension of the wrist will be more painful if resistance is given at the heads of the metacarpals rather than at the fingertips.⁸ Radial extension will more specifically indicate the ECRB or ECRL. Tenderness above the epicondyle will indicate that the ECRL is involved, while anterolateral tenderness would arise from ECRB tissue inflammation. ²

Once a muscle fatigues the tendon accepts the kinetic forces hence the reason tendinopathy injuries are observed in overuse repetitive type athletes. Main components comprising tendinopathy are angiofibroblastic hyperplasia which is an internal misalignment of collagen fibers. Each time the degenerative tendon is further worked it restarts the fibroblastic phase of healing laying down new Type III collagen which further degenerate the components of a normal tendon. ¹¹

The onset of pain is usually gradual. The simple diagnostic tests can include the forced elbow extension test, which is usually positive. The forearm is held fully pronated and the wrist palmarly flexed; passive elbow extension then produces lateral elbow pain, which may limit full extension of the joint. Grip strength is limited by pain, as measured by dynamometry. As opposed to tenderness to palpation of the lateral epicondyle and isometrically resisted extension of the wrist, signifying true LE.²

Majority of treatment protocol for the management of LE ranges from Anti-Inflammatory Medication, Corticosteroid Injection, Electrical stimulation, LASER, acupuncture, counterforce Bracing or Splint, Ergonomics, Ultrasound, Iontophoresis, Phonophoresis, exercises (Flexibility, Strengthening and Endurance training), Manual therapy techniques, (e.g., Transverse Frictions, Joint mobilization and manipulation, Myofascial release, strain and counter strain techniques) etc.⁵

Therapeutic exercise programs reduce pain and improve function. Literature has found connections between eccentric loading and positive outcomes in tendinopathy patients by inducing hypertrophy, increasing tensile strength and decreasing neovascularization. Eccentric contraction can create a greater stimulus for the cells of the tendon, producing collagen and resulting in the tendon being able to withstand greater forces. It is believed that neovascularization is a causing factor of pain in LE and other tendinopathies. Eccentric execution results in greater force production with less energy expenditure and less oxygen consumption compared to concentric execution.¹³Recent evidence suggests that eccentric actions may be more effective, but must be used with caution due to the common effect of muscle soreness.^1,10,14

Based mainly on clinical experience, supinator weakness in LE patients is commonly addressed as increasing pain, and decreasing functional ability and hand-grip strength. This means that the causes of LE may not be Limited to the ECRB. Functional impingement of the supinator due to altered joint mechanism   and muscle imbalance   can   impair the stabilization   of the elbow   resulting   in

overcompensation of the ECRB. Changes in supinator may lead to altered and compensatory changes