Functions of the Achilles Tendon
The Achilles tendon originates from the merging of the soleus and gastrocnemius and inserts distally onto the calcaneus. The tendon is surrounded by paratenon made up of a single layer of cells, this tissue contributes to the blood supply of the tendon. The functions of the Achilles tendon are to absorb loads placed on it by the body, and to help flex the ankle joint. Tendons have high mechanical strength, good flexibility, and allow a certain amount of elasticity to perform their unique role (Kirkendall & garrett, 1997). If this amount of elasticity is exceeded, stress is placed on the tendon causing an overload. If this overload is repeated, without sufficient recovery time, injury may occur.
Causes of Achilles Tendonitis
Damage to the Achilles tendon is referred to as Achilles tendinopathy. Johnston, et al. (1997) states that Achilles tendinopathy is, ‘one of the most common overuse injuries among recreational athletes, accounting for up to nine percent of injuries in elite and recreational runners .’ It can also affect athletes participating in racquet sports, track and field events, volleyball and soccer, generally in sports that require running or explosive activity. During sprinting ‘the tendon experiences forces as high as 12.5 times body weight’ (Komi, et al. 1992). This is an example of how much stress the tendon is put under and shows that repeated stress can cause damage to the tendon. Achilles tendinopathy can also occur in patients with tight gastrocnemius and soleus. This is due to the same principle that increased stress is placed on the tendon.
Achilles tendinopathy can be acute or chronic and caused by intrinsic and extrinsic factors. Intrinsic factors such as tendon vascularity, gastrocnemius and soleus dysfunction, age, gender, body weight and height, pes cavus, excessive subtalar joint pronation, limited passive dorsi flexion or subtalar joint mobility can all bring on symptoms of Achilles tendinopathy. Extrinsic factors are changes in training pattern, poor technique, previous injuries, footwear and environmental factors such as training on hard, slippery or slanting surfaces. A number of studies have been carried out in the area of age and Achilles tendinopathy. A study into Achilles tendon pain in middle-aged competitive badminton players concluded that Achilles tendon injuries increased with age (Alfredson, et al. 2001). Sandrey (2003) and Leadbetter(1997) also agreed that age was an influencing factor. Schepsis, et al. (2002) proposed that Achilles tendinopathy was three times more likely to occur in men than women. However, a study into Achilles tendon pain and eccentric calf muscle training tested men and women of different ages, and found no links between Achilles tendinopathy and age and gender.
Symptoms of Achilles Tendonitis
The term tendinopathy has only come into use in recent years, it’s used to describe all Achilles tendon disorders. The term Achilles tendonitis was used to describe inflammation of the tendon, however, many studies have shown that chronic Achilles tendon disorders are more often a degenerative condition rather than an inflammatory condition (Leadbetter, et al. 1997, Khan, et al. 2000). With the main symptom being pain, investigators were confused as to why, in some cases, inflammation was not present. It is thought that pain may originate from a combination of mechanical and biomechanical causes.
Other signs include tendon thickening, thickened nodules, and a soft feeling in the tendon when palpated compared to the other limb. Myerson and McGarvey (1999) found that in addition to these symptoms a marked weakness and a decrease in push off strength were also present. Research has found that many patients will complain of pain in the morning when they step out of bed. This is due to most people sleeping with their ankles in plantar flexion, so when the foot is placed on the floor the tendon lengthens, causing pain. This suggests that exercising and keeping the tendon mobile are important in treating the condition.
- Sandrey, M. (2003) ‘Acute and Chronic Tendon Injuries: Factors Affecting the Healing Response and Treatment’ Journal of Sports Rehabilitation. 12 pp. 70-91.
- Myerson, M., McGarvey, W. (1999) ‘Disorders of the Achilles tendon insertion and Achilles tendonitis’ Instructional Course Lectures. 48 pp. 211-218.
- Kvist, M. (1994) ‘Achilles tendon injuries in athletes’ Sports Medicine. 18 pp. 173-201.
- Schepsis, H., Jones & Haas, A. (2002) ‘Achilles tendon disorders in athletes’ American Journal of Sports Medicine. 30 (2) pp. 287–305.
- Fahlstrom, M., Lorentzon, R., Jonsson, P. & Alfredson, H. (2003) ‘Chronic Achilles Tendon Pain Treated with Eccentric calf-Muscle Training’ Sports Medicine. 11 pp. 327-333.
- Fahlstrom, M., Lorentzon, R. & Alfredson, H. (2002) ‘Painful Conditions in the Achilles Tendon Region: A Common Problem in Middle-aged Competitive Badminton Players’ Sports Medicine. 10 pp. 57-60.
- Komi, p., Fukashiro, S. & Jarvinen, M. (1992) ‘Biomechanical Loading of Achilles TendonDuring Normal Locomotion’ Clinical Sports Medicine.11 pp. 521-531.
- Johnston, E., Scranton, P. & Pfeffer, G. (1997) ‘Chronic Disorders of the Achilles Tendon: Results of conservative & Surgical Treatment’ Foot & Ankle International. 18 (9) pp. 570-574.