Achilles Tendinopathy

Achilles Tendinopathies

are overuse injuries that arise when the tendon has been overloaded. The achilles tendon, the strongest tendon in our body, is subjected to very high loads and is thus vulnerable to overuse as a result of the cumulative loading. Typically a mid-portion tendinopathy is seen with the achilles (occurring at the midsection of the tendon) but insertional tendinopathies may also occur (happening where the tendon meets the bone).

Pathophysiology (the disease process):

When optimally loaded at a consistent and regular pace, tendons are able to undergo an adaptation process whereby they strengthen and are capable of withstanding greater loads. When loaded excessively with or without the presence of individual risk factors, tendons are unable to withstand normal amounts of load and enter a reactive stage where the tendon now reacts to load. If a tendon in the reactive stage is identified early, implementing appropriate load modification strategies will be able to resolve the tendon to its usual, healthy status. However, upon continuation of excessive loading, this can lead to tendon dysrepair which advances to degenerative tendinopathy.

So we can think of the stages of an achilles tendinopathy as a continuum of pathology. A reactive tendinopathy characteristically has increased cell number and activation. This causes thickening of the tendon and a short-term reduction in stress. Often the reactive stage occurs in an acutely overloaded tendon and/or through direct trauma.

The stage of tendon dysrepair is a worsening pathology whereby greater tendon breakdown occurs. Cells are more prominent, a greater production and separation of collagen occurs, disruption of the cell matrix is evident, and the growth of blood vessels and nerves to assist with the healing process causes symptomatic changes (pain, stiffness, reduced range). Usually this stage produces noticeable changes on ultrasound or MRI.

Degenerative tendinopathy, considered the end stage of disease following long-term tendon overload (generally > 3 months), pertains to cell apoptosis (death) alongside the progression of matrix changes. Greater disorganisation is apparent with more blood vessels forming which cause swelling and pain. Tendon rupture is possible at this end-stage.

Figure 1: Tendon Pathophysiology

Presentation of Achilles Tendinopathies:

Achilles tendinopathies commonly present in runners and sports involving frequent running and jumping. Typically, it is a gradual onset injury that is aggravated during or after activities – frequently the morning after. It is possible for pain to disappear after warming up and this is often why individuals continue training when a tendinopathy is present, especially in the early stages of the condition.
… But what does it actually look like?

When feeling around the achilles tendon there is tenderness and thickening.
Pain localised to the tendon region.
Occasionally, crepitus is present.
Pain when loading the tendon. A common test is a heel rise (calf raise) test. Repetitive heel raises will elicit symptoms of pain.

Confirmation of diagnosis through imaging can be done via ultrasound, ultrasound tissue characterisation, or MRI. It is however, important to note that tendons can be painful and symptomatic even if they appear normal on imaging.

Risk Factors of Achilles Tendinopathy:

Intrinsic Risk Factors include:

Weakness in the plantarflexor muscle bulk which results in more load on the tendon itself.
Weakness in other muscles in the kinematic chain (e.g. knee flexors) – increases the demand further down the chain.
Increased or reduced dorsiflexion range of motion increases the tendon load by changing the loading period and velocity and increasing the lever length.
Poor quality tendon structure which reduces the capacity of the tendon to tolerate load and predisposes it to injury.
Length of the gastrocnemius (calf) muscle.
Foot mobility.

Extrinsic Risk Factors include:

Recent changes in loading of the tendon:
❖ Increased training (speed, distance, number of sessions, duration, intensity).
❖ Footwear.
❖ Insufficient recovery time between sessions.
❖ Increased activities with high energy storage (e.g. jumping and landing).
❖ Training surfaces.

Stages of Rehabilitation

Achilles tendinopathy rehabilitation involves symptom management, identifying factors which increase the tendon load and intervention to address contributing factors and improve tendon strength. After an initial period of offloading, exercise is deemed the best intervention for tendinopathies and rehabilitation needs to occur in a staged approach, considering factors of strength, energy storage, and energy release.

Initial offloading of the achilles tendon can be done via a heel insert. After the acute period of injury and pain, it is important to re-expose the musculo-tendinous unit to load. To prevent future flare ups, it is also essential to address potential causal factors such as the risk factors mentioned previously.

Stage 1 – Isometric Exercise:

Purpose: To provide pain relief. Pain relief can take up to 8 weeks in the reactive stage of tendinopathy compared with 7-10 days in the degenerative stage.
Hold a heel raise position for up to 45 seconds with bodyweight in single or double leg stance. Repeat 4-5 times with rest in between. Repeat several times a day.

Stage 2 – Isotonic Exercise:

Purpose: To improve strength.
Concentric and eccentric exercise components with an extended eccentric component. Slow and heavy movements will help develop strength. Development of strength may take up to 12 weeks. For example, complete heel raises going up and down but slow the timing of the descent.
Alfredson’s model of eccentric heel drop exercises (3 sets of 15 repetitions, 2 times daily) has been widely adopted for achilles tendinopathy rehabilitation with significant evidence showcasing its role in tendon strengthening and repair.
Aim to train every muscle group that has a functional deficit; Glutes, Quadriceps, Hamstrings and Gastrocnemius.
It is important to continue this stage (isotonic exercises) throughout and following rehab.

Stage 3 – Energy Storage Exercise

Purpose: To load the tendon with energy storage movements upon gaining adequate muscle strength.
Complete faster eccentric exercises with a slower concentric phase. It is reasonable to start with bodyweight activities and gradually progress to the addition of loads.
Exercise examples include skipping, fast stair climbing. Complete these 2-3 times per week on alternating days to prevent overloading the tendon.

Stage 4 – Energy Storage and Release (Sport)

Purpose: To challenge the muscle-tendon unit in a functional, activity-specific manner that is a progression from stage 3.
Stage 4 promotes a return to sport-specific movements and training via completing movements with faster speed and release of energy and moving further into loading at end-ranges.
The tendon can be loaded through running drills, changing of direction and jumping type movement patterns in stage 4.

Are Insertional Achilles Tendinopathies any Different?

Insertional achilles tendinopathies involves the lower portion of the tendon where it inserts into the calcaneus and often coincides with retrocalcaneal bursitis. Excessive tendon loading and pulling limits the space between the tendon and bone, compressing against the bursa, and causes dorsiflexion to become an issue. Management of an insertional achilles tendinopathy follows the same stage progression approach as a typical (midportion) achilles tendinopathy; however, loading into dorsiflexion should be avoided as well as stretching. This is to present compression and irritation of the bursa.

Figure 2: Eccentric Training, Alfredson Model

Figure 3: Tendinopathy rehabilitation schematic

References:

Simic, M. Tendinopathy: Aetiology and Interventions. PHTY2058: Physiotherapy in Musculoskeletal Conditions A. 2022.
Silbernagel, K. G., Hanlon, S., & Sprague, A. (2020). Current Clinical Concepts: Conservative Management of Achilles Tendinopathy. Journal of athletic training, 55(5), 438–447. https://doi.org/10.4085/1062-6050-356-19
Alfredson, H., & Cook, J. (2007). A treatment algorithm for managing Achilles tendinopathy: new treatment options. British journal of sports medicine, 41(4), 211–216. https://doi.org/10.1136/bjsm.2007.035543
Warden w (2017). Sports injuries: overuse. Brukner P, & Clarsen B, & Cook J, & Cools A, & Crossley K, & Hutchinson M, & McCrory P, & Bahr R, & Khan K(Eds.),Brukner & Khan’s Clinical Sports Medicine: Injuries, Volume 1, 5e. McGraw Hill. https://csm.mhmedical.com/content.aspx?bookid=1970&sectionid=168688996
Achilles tendinitis – orthoinfo – aaos. OrthoInfo. (n.d.). https://orthoinfo.aaos.org/en/diseases–conditions/achilles-tendinitis/
Tendon pathophysiology. Physiopedia. (n.d.). https://www.physio-pedia.com/Tendon_Pathophysiology
Progressions for muscle and tendon rehab – sspc.com.au. (n.d.). https://www.sspc.com.au/wp-content/uploads/2020/05/SSPC-Clinician-Information-Muscle-and-Tendon-Load-Progression.pdf
Ryg, J. (2017, February 2). Why is eccentric exercise helpful for achilles tendinopathy?. Mend. https://www.mendcolorado.com/physical-therapy-blog/2015/9/16/why-is-eccentric-exercise-helpful-for-achilles-tendinopathy