Musculoskeletal Disorders. Sean Gallagher
Characteristics/description
Lateral epicondylitis (commonly referred to as “tennis elbow”) is a disorder characterized by pain at or near the lateral epicondyle of the humerus. The pain may be localized to this region, may radiate down the extensor muscle group of the forearm, and occasionally may radiate proximally to the upper arm (Vaquero‐Picado, Barco, & Antuña, 2017). This pain can be triggered or exacerbated by contraction of the common extensor mass in response to a variety of activities (Ahmad et al., 2013). Tenderness is most often exhibited at the site of the attachment of the extensor carpi radialis brevis (ECRB) tendon; however, pain and tenderness on palpation can also be experienced around the prominence of the lateral epicondyle. Pain intensity can be quite variable and manifest as intermittent and mild to constant and severe. The latter can affect a wide range of daily activities and may even occur at night, thereby causing a disturbance in sleep.
Epidemiology
Studies suggest that the prevalence of lateral epicondylitis in the general population in the United Kingdom is approximately 1–3% and is more common in adults aged 35–55 years. Gender does not appear to play a significant role as to prevalence (Smidt & van der Windt, 2006). However, the examination of the prevalence rates of lateral epicondylitis in working populations provides a different picture. A study of the prevalence of lateral epicondylitis among workers at 12 worksites indicated a prevalence rate of 5.2% in the dominant arm (Fan et al., 2009). A Finnish study found that the true incidence of lateral epicondylitis was due to the overuse of or change in biomechanics as a result of elbow pain (Shiri, Viikari‐Juntura, Varonen, & Heliövaara, 2006). Incidence was found to be variable depending on the criteria used to confirm the diagnosis. They found it to be definitely present in 1.3% of the population between the ages of 30 and 65 years and likely present in a further 2.98%.
Anatomy/pathology
In lateral epicondylitis, it is believed that a common extensor tendon (a conglomeration of the tendons of the extensor carpi radialis brevis, the extensor digitorum, the extensor digiti minimi, and the extensor carpi ulnaris) is affected by progressive process of inflammation and then degeneration (Figure 2.5). The degeneration of the tendon is the result of repetitive application of stress, leading to the microtear development in the common tendon (Kraushaar & Nirschl, 1999). The accumulation and growth of microtears is the process by which tendinosis initiates and propagates in the tendon. If the tendon continues to experience stress in this region, these pathologic changes may ultimately lead to partial or complete rupture of the tendon (Kraushaar & Nirschl, 1999).
Figure 2.5 Location of inflamed or injured tissues in the extensor carpi radialis brevis (ECRB) tendon.
Jacobson, J. A., Chiavaras, M. M., Lawton, J. M., Downie, B., Yablon, C.M., & Lawton, J. (2014). Radial collateral ligament of the elbow: Sonographic characterization with cadaveric dissection correlation and magnetic resonance arthrography. Journal of Ultrasound in Medicine, 33(6), 1041–1048. DOI: 10.7863/ultra.33.6.1041. Wiley.
Risk factors/activities associated with lateral epicondylitis
As the nickname “tennis elbow” suggests, this disorder is often associated with activities that require repetitive or prolonged gripping activities (such as a tennis racquet when playing tennis). Occupationally, tasks that require forceful, prolonged, or repetitive use of hand tools are often associated with the development of lateral epicondylitis. This disorder is also associated with the use of powered hand tools, such as hand drills or other powered drivers requiring repetitive and forceful exertions involving the forearm extensor muscles, especially if such activities are required of the worker throughout an entire workday. In addition, handling tools greater than 1 kg, weights in excess of 20 kg (more than 10 times per day), and repetitive activities greater than 2 hour/day have been implicated as occupational risk factors for lateral epicondylitis (Ahmad et al., 2013).
Medial elbow tendinopathy
Characteristics/description
Medial epicondylitis is an overuse tendinopathy due to chronic repetitive concentric or eccentric loading of the wrist flexors and pronator teres, resulting in angiogenic and fibroblastic changes (Kiel & Kaiser, 2019). Although epicondylitis is most commonly experienced on the lateral side of the elbow, certain activities (often occupational tasks) that cause repeated stress on the elbow can lead to pain and discomfort affecting the medial epicondyle. Pain associated with medial epicondylitis is often localized to the medial epicondyle, sometimes with radiation to the proximal forearm (Amin, 2015). Pain associated with medial epicondylitis is often increased in activities involving wrist flexion or pronation (Kiel & Kaiser, 2019) This pathology is due to the development of microtrauma and degeneration of the common flexor tendon and is most commonly seen in patients above 40 years of age (Amin, 2015). The prognosis for medial epicondylitis is generally quite favorable. Most patients can return to work or athletic activities after activity modification and/or physical therapy treatment (Kiel & Kaiser, 2019).
Epidemiology
Medial epicondylitis is much less prevalent than lateral epicondylitis; however, this disorder still accounts for approximately 10–20% of all epicondylitis (Shiri et al., 2006). According to one study, the prevalence in the general population is quite low, with only 0.4% afflicted. A significantly higher prevalence can be found in individuals participating in activities that repeatedly stress the tendons making up the common flexor tendon (i.e., the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and the flexor digitorum superficialis) (Kiel & Kaiser, 2019). In some occupational settings, the prevalence of medial epicondylitis has been found to range from 3.8 to 8.2% (Shiri et al., 2006; Descatha et al., 2003; Wolf et al., 2010). Three out of four cases are in the dominant arm. Medial epicondylitis is highest among subjects aged 45–64. Some studies suggest that the prevalence of this disorder in men and women appears roughly equivalent (Amin, 2015), but others have suggested greater prevalence in women (Kiel & Kaiser, 2019).
A study examining the prevalence of medial epicondylitis across five industrial sectors was reported by Descatha et al. (2003). This study indicated prevalence between 4 and 5%, with annual incidence estimated at 1.5% for this disorder. Forceful work was found to be a risk factor for medial epicondylitis but not exposure to repetitive work. Risk factors differed for medial and lateral epicondylitis. The prognosis for medial epicondylitis in this population was good with a 3‐year recovery rate of 81% (Descatha et al., 2003). A later study suggested that forceful and repetitive wrist bending, forceful gripping, and rotating/twisting actions of the forearm were significantly associated with medial epicondylitis (Descatha, Dale, Jaegers, Herquelot, & Evanoff, 2013). Odds ratios for these three physical factors were not significant for exposures less than 2 hr/day, but all were significant for exposures greater than 4 hr/day. These findings suggest that repetition (in combination with force) was an important factor in the development of medial epicondylitis in these workers.
Anatomy/pathology
The pathology associated with medial epicondylitis is similar to that of lateral epicondylitis; however, different activities may provide the requisite stress on the flexor tendons compared to those affecting the extensor tendons. As with medial epicondylitis repetitive activity leads exposure to forceful and repetitive activities is thought to lead to recurrent microtears in the tendon