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Achilles tendon rupture (ATR) is a frequent and disabling injury. In the last decade the incidence of ATR has been increasing and is suffered more by men than women. Plantar flexion strength decrements and endurance impairments are observed in patients with ATR whether treated surgically or non-surgically.

Factors associated with good recovery are yet to be determined, particularly in non-surgically treated patients. The aim of this thesis was to examine Achilles tendon (AT) and triceps surae (TS) muscle-tendon unit biomechanics in non-surgically treated patients 1-year after ATR.

The body adapts and compensates injuries

The result shows that the Achilles tendon heal to an elongated length. The remodeling of the calf muscles result in strength decrements that in many patients last for more than one year. The results suggest that restoration of calf muscle force and thereby tendon stiffness leads to better recovery.

The body is adaptable and can compensate injuries by using alternative strategies and pathways of force transmission.

— In the case of Achilles tendon rupture, our results showed increased activity of the flexor hallucis longus (FHL) which is a deep flexor muscle that attach to the big toe and are capable of plantar flexion, tells Ra’ad Khair.

Because the FHL muscle is not as strong nor situated in a way to fully compensate the calf muscles attached to the Achilles tendon, rehabilitation should aim to restore calf muscle function and not to focus on toe flexors to compensate for the deficiency.

A new way to scan the Achilles tendon

Previously it was thought that the AT function as one uniform unit, but there is differential movement within the tendon. We used ultrasound imaging and advanced processing algorithms and found more uniform movement after Achilles tendon rupture in non-surgically treated tendon compared to healthy leg.

— Interestingly, the tendon internal displacement pattern was not different between legs suggesting that non-surgical treatment may preserve normal organization within the Achilles tendon, explains Khair.

Furthermore, in this study a novel method was developed that enables to scan subtendons within the AT adjacent to the originating muscles. This novel method may enable individual patient-specific rehabilitation protocols in the future.

The research was conducted in collaboration with Central Finland Hospital Nova. The data was from total of 83 individuals.

M.Sc. Ra'ad Khair defends his doctoral dissertation "Biomechanical recovery factors in non-surgically treated ruptured Achilles tendons" on 25.08.2023 at 12:00 in Seminaarinmäki lecture hall L303. Opponent is Professor S. Peter Magnusson (University of Copenhagen, Denmark) and Custos Professor Taija Juutinen Finni (Ä¢¹½Ö±²¥). The doctoral dissertation is held in English.

Live broadcast is available at

Publication details

The thesis "Biomechanical recovery factors in non-surgically treated ruptured Achilles tendons" is available in the JYX repository: