Foot and ankle injuries represent a large proportion of all injuries resulting in time lost to sport. In high level college sport, it is estimated to account for 27% of all injuries, whilst some studies investigating the prevalence of foot and ankle injuries in recreational sport could exceed 35% of all injuries.
In Australia, around 20% of people identify as having chronic ankle dysfunction, demonstrating the ongoing burden of these injuries and potentially highlighting the insufficiencies of the rehabilitation process.
Why do so many people have ongoing ankle dysfunction post injury?
Many people consider ankle injuries as ‘minor’ or insignificant injuries, requiring a short period of rest to facilitate recovery, before an expected restoration of normal function. However, the evidence is clear that many ankle injuries result in significant ongoing functional deficits, such as reductions in local muscle strength, decreases in reactive strength (power), deficits in proprioception (joint position sense), as well as static and dynamic balance and resultant compensations within other parts of the kinetic chain. Our clear, criteria-driven approach to rehabilitation aims to address each of these impairments, to optimize return to function and performance concurrently.
In the acute period post injury, a primary goal is to maintain activity levels, whilst allowing the pain to settle. This is facilitated with regular, low-intensity muscle contractions to aid in the removal of excessive swelling and promote optimal healing within the local tissues. This is often complemented with basic management principles, such as elevation and compression to further aid in removal of excessive fluid from the injured site. During this period, low-impact proprioception, dynamic balance and range of motion exercises will be commenced. Criteria to pass through this early stage of rehabilitation includes:
– Star excursion balance test within normative data, relative to gender, height and sport.
– A weight-bearing lunge (otherwise known as a knee to wall) test, assessing ankle dorsiflexion range of motion, within 10% of the unaffected limb, or more than 9cm.
– Repeated single-leg squat, assessing gross lower-limb strength and function, as well as the integration of the foot and ankle to a global movement task.
– Time to stabilization within normative range, as measured during a single-leg drop landing from a 15cm box with our cutting-edge Vald ForceDecks.
Local muscle strength
When an area of the body is under-loaded after an injury, the body loses muscle mass very quickly. This process is known as muscle atrophy. To minimize the rate at which local muscle atrophies, we aim to progressively load the surrounding tissues as early as possible. As mentioned above, this often commences with small volumes of exercise, frequently throughout the day. As excessive swelling is removed from the local region and normal blood flow is returned, it is appropriate to progress the intensity and volume of exercise to promote increases in muscle growth and strength. The key local muscles which are targeted in this phase include the muscles of the calf, the muscles in the front of the lower-leg and ankle which flex the ankle upwards, and the intrinsic foot muscles. Calf strength is well recognized in rehabilitation, as the calf is one of the primary muscle groups which attenuates load through the ankle joint during walking, running and jumping tasks, to name a few. The ankle dorsiflexors (those at the front of the lower leg and ankle) help to balance the force of the calf muscles, minimizing shear force across the ankle joint. Important (and often neglected) in rehabilitation is the structure and function of the intrinsic muscles of the foot. These small muscles have an extremely high density of stretch receptors, known as ‘muscle-spindles’. These receptors signal subtle changes in muscle length, which informs the brain of movement, and helps regulate muscle stiffness to maintain balance and optimize function. Local strength progression criteria includes:
– Great toe plantarflexion strength (used as a proxy for intrinsic muscle function) between 2.9-3.5N.kg-1 (as determined by a number of factors, relative to body composition, sport, position, distribution of physical characteristics)
– Calf capacity (endurance) testing, consisting of controlled, single-leg body-weight calf raises, set to a metronome.
– Standing calf raise peak force (which biases the gastrocnemius muscle) greater than 28N.kg-1.
– Seated calf raise peak force (which biases the soleus muscle) greater than 16N.kg-1.
– Ankle dorsiflexion (foot / toes pulled up) peak force greater than 5N.kg-1.
Reactive Strength / Power
Most sports, especially field-based or multidirectional sports require large force to be applied in a very short period of time (think about how short the contact time is during a sprint, for example). As such, the ability of the muscle-tendon units of the lower limb to function like springs is crucial. Underpinning this quality is the ability of the muscle system to produce high contractile force and the tendons which they connect to possessing high levels of stiffness. This tendon stiffness assists with the transfer of energy, allowing the lower limb to efficiently operate for extended periods of time7. Reactive strength assessment and progression criteria consists of:
– Single and double-leg drop jumps (stepping off a box and jumping as high as possible as soon as the foot / feet touch the ground). One of the key metrics assessed during these tests is a reactive strength index (RSI). This is assessed using the Vald ForceDecks, by dividing the jump height by the contact time. Specific values vary from individual to individual based on their sport, body composition, position, to name a few. Typical target RSI scores for double-leg and single-leg drop jumps are 1.5-2.0 and 0.6-0.9 respectively. For a valid and reliable test, the foot contact times are generally required to be less than 0.3 seconds for double-leg drop jumps and 0.25 seconds for single-leg drop jumps.
– Coordinated multidirectional hopping tasks, such as cone / low hurdle hopping, forwards, backwards, side-ways and with rotation, with <10% asymmetry in time to completion and landing accuracy errors.
Running Gait Assessment
For return to running-based sport, it is prudent to assess running mechanics to identify and factors which may contribute to recurrent injury or lower-limb segmental overload, whilst improving performance concurrently. This is typically performed at steady-state speeds (assessed whilst running indoors on a treadmill) and during high-speed running / sprinting (on field). This is an important differentiation, as the two tasks have very different technical demands7,8. Assessment is performed using kinematic video analysis software, identifying a variety of key factors, such as:
– Ground contact times and asymmetries
– Pelvic control and position of centre of mass at foot strike
– Vertical and horizontal displacement of the centre of mass
– Running cadence
– Mid / rear-foot pronation during mid-stance
– Hip, knee and ankle flexion angles at mid-stance (with larger joint angles leading to increased contact time and greater load of the distal segments)
– Hip, knee and ankle angles at toe-off (which primarily effects contact time and joint excursion)
How We Can Help
1 Hunt, K. J., Hurwit, D., Robell, K., Gatewood, C., Botser, I. B., & Matheson, G. (2017). Incidence and Epidemiology of Foot and Ankle Injuries in Elite Collegiate Athletes. The American journal of sports medicine, 45(2), 426–433.
2 Luciano, A., & Lara, L. C. (2012). Epidemiological study of foot and ankle injuries in recreational sports. Acta ortopedica brasileira, 20(6), 339–342.
3 Hiller, C., Nightingale, E., Raymond, J., Kilbreath, S., & Burns, J., Black, D., Refshauge, K. (2012). Prevalence and Impact of Chronic Musculoskeletal Ankle Disorders in the Community. Archives of physical medicine and rehabilitation. 93. 1801-7.
4 Dejong, A. F., Koldenhoven, R. M., & Hertel, J. (2020). Proximal Adaptations in Chronic Ankle Instability: Systematic Review and Meta-analysis. Medicine and science in sports and exercise, 52(7), 1563–1575.
5 Khalaj N, Vicenzino B, Heales LJ, et al. (2020). Is chronic ankle instability associated with impaired muscle strength? Ankle, knee and hip muscle strength in individuals with chronic ankle instability: a systematic review with meta-analysis. British Journal of Sports Medicine;54:839-847.
6 Thompson, C., Schabrun, S., Romero, R., Bialocerkowski, A., van Dieen, J., & Marshall, P. (2018). Factors Contributing to Chronic Ankle Instability: A Systematic Review and Meta-Analysis of Systematic Reviews. Sports medicine (Auckland, N.Z.), 48(1), 189–205.
7 Green B, Pizzari T. Calf muscle strain injuries in sport: a systematic review of risk factors for injury. British journal of sports medicine. 2017 Aug 1;51(16):1189-94.
8 Hunter GR, McCarthy JP, Carter SJ, Bamman MM, Gaddy ES, Fisher G, Katsoulis K, Plaisance EP, Newcomer BR. Muscle fiber type, Achilles tendon length, potentiation, and running economy. The Journal of Strength & Conditioning Research. 2015 May 1;29(5):1302-9.