Achillies Tendonopathy
Martin Krause

The Achilles tendon is the thickest and strongest tendon in the body. It is responsible for the power of push off and landing and has been suggested to be able to transmit force of up to 7 times body weight. However, even Homer in the Iliad espoused it's vulnerability. Achilles tendonopathy commonly involve degenerative changes, sometimes associated with a micro tear and may occasionally be accompanied by inflammation and oedema in the paratendonous structures. Biomechanical and metabolic reasons have been associated with etiology and chronicity.

Tightness in the calf places increasing strain on the tendon, reduces the range of dorsiflexion in the ankle and consequently increasing the amount and duration of pronation. Prolonged and excessive pronation reduces the ability of the foot to become rigid lever at push off due to it's subsequent limitation of supination. Alterations of the timing of pronation-supination can translate into altered rotation of the tibia at the knee and subsequent compensatory rotation at the hip. The hip can therefore appear functionally weak in rotation. Hence, strength and control of the lateral rotators and iliacus need to be determined whenever treating an achilles tendonopathy.

Further etiological factors have included stiffness in the talocrural joint to dorsiflexion, and the subtatlar joint to both inversion/eversion as well as plantarflexion. The posterior tibial compartment has been implicated in functional weakness of the medial forefoot. Additionally, there appears to be an important contribution of stability from the lateral compartment (peroneal muscles), as recurrent ankle sprains seem to be associated with a high incidence of Achilles tendonopathy. Presumably, at push of there is an inordinate amount of strain on the lateral aspect of the tendon due to increased inversion of the foot. This would also result in lack of strain in the medial aspect which can cause collagen atrophy. Finally, inversion would also reduce the ability of the foot to lock into supination at push off, therefore placing greater demands on the lateral stabilisers (gluteus medius, anterior, lateral and posterior portions) and extensors of the hip in walking and sprinting respectively. Therefore, stabilising factors need to be assessed and built into a rehabilitation programme. These, may include theraband exercises, balance training on foam or wobble boards as well as a low load endurance lumbopelvic-abdominal stabilisation regime. Shoes and Orthotics will also need consideration (see figures). Later, where performance enhancement is critical a Swiss Ball may also become an invaluable tool for higher intensity lumbopelvic stability.

Inverse dynamics suggests that the 2 joint muscles are energy straps which transfer energy from one segment to the next. During push off, the gastrocnemius provides an extensor torque around the ankle which transfers energy from the foot to the femur. This is countered by an extensor torque in the knee transfering energy into the pelvis, which is countered by an extensor torque in the hip through the momentum of body weight coming forward. On landing the reverse occurs whereby the placement of the forefoot on the ground begins the energy absorbing eccentric component of plantarflexion to dorsiflexion, knee extension to flexion, hip flexion to extension. In the this phase the stabilising 'catch' of the inferior gluteus maximus is particularly important to stabilise the pelvis, whilst the knee extensors dampen flexion torque as does the gastrocnemius. Due to this elastic and potential energy the system can become a very efficient spring designed to capture energy as well as release energy during recoil. Whereas, the majority of soft tissues only have 2-4% elasticity, muscles can elongate and recoil over several centimetres. Therefore, eccentric-concentric training of the entire kinetic chain, beginning with the Swedish protocol of 'heel drops" and even eventually involving plyometrics is essential to fully recover from Achilles tendonopathy.

Cause and effect are difficult to determine biomechanically. A thorough clinical history determining the locations and timing of previous injuries, and/or estimating areas which have been particularly loaded or neglected through activities of daily living needs to be carried out. The physical examination should encompass an inspection of the Achilles. Furthermore, assessment of gait and any other functional activity should help clarify the contributions of the muscles and joints at the ankle-foot, knee, hip and lumbar spine to the efficiency of the entire kinetic chain. Observations need to be confirmed through palpation of joints and soft tissue structures as well as examination of muscle strength, endurance and co-ordination. General consensus suggests that the tendon is vulnerable to poor recovery from injury due to it's nutritional constraints. Reduced efficiency increases the metabolic demands of locomotion, thereby diverting energy way from the healing process. Therefore, the examination will need to clarify the cause of the cause, as well as prioritise the focus of treatment.

When designing a treatment regime, the Achilles tendon needs to be considered as a functional metabolic and biomechanical unit. Tightness in the calf not only places greater strains on the tendon, but also compromises blood flow and diffusion of nutrition to the tendon, which in turn can create greater metabolic constraints. Motor-cognitive deficits may be addressed and overcome relatively rapidly, however the biological time constraints of healing suggest anywhere from 6 weeks to 6 months for recovery to take place. Rehabilitation incorporating joint mobilisations, soft tissue techniques, and exercise regimes will require an understanding of biomechanics, inflammation and the stages of healing. Due to the potentially long recovery time, some cognitive behavioural strategies for goal implementation may need to be established.

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