A Summary of Inversion at the Subtalar Joint

Author: Kevin B. Rosenbloom, C.Ped, Sports Biomechanist

The articulating surfaces within the ankle and foot provide for several complex movements, inversion being one of them. The following summary will review the contributing muscles, the range of motion and some research that can peak the interests of the inquiring mind.


Inversion at the ankle is the superior raising along the medial side of the foot, thus revealing its the plantar surfaces to the sagittal (median) plane. The muscles that provide contribution to this motion are both tibialis muscles (posterior, anterior), both tibial flexor muscles (f. digitorum longus, f. hallucis longus) and the extensor hallucis longus (Visible Body 2019).

Range of Motion

Among the sources used for data collection in this article has found some consensus in the range of motion for inversion. A mean range of 30° (Washington State DSHS 2014) with a deviation of 5° in other sources. Less flexible individuals has been observed to have a range of up to 15° with individuals with her flexibility reaching up to 50° of inversion (Roaas & Andersson 1982).

Muscle Contributors

Each muscle in the leg that contributes to inversion has been discussed in previous articles. To prevent monotony in these summaries, it is suggested to review those past articles. Links to the articles will be listed just below this paragraph. However, each invertor muscle’s origins, insertions and additional actions will be described below in the Muscle Overview portion of this summary.

Tibialis posterior, flexor digitorum longus & f. hallucis longus - Ankle plantar flexion summary
Tibialis anterior, extensor hallucis longus - Ankle dorsiflexion summary


Clinicians have extended experience seeing patients with ankle inversion injuries. Ankle sprains appear to be one of the most common ailments observed not only in an athletic environment, but also in daily life. In a study by Beckman & Buchanan, they compiled a great list of some ankle sprain statistics, including that up to 85% of all ankle sprains are related to injuring the lateral ligaments specifically. With the experimental research, both authors explored the results of chronic ankle inversion and hypermobility and its effects on other portions of the lower extremities. In general, what was concluded was that nerve receptors could experience delay, superior pelvic displacement occurred and the latency of muscle activation in the hips and legs were altered (Beckman & Buchanan 1995). These results can provide useful information to clinicians and physical therapists while planning out patients’ treatment plans.

Muscle Overview - Ankle Invertors

Figure 1. Sketch of right ankle invertors, posterior view (left) and anterior view (right).

Figure 2. Sketch of right ankle invertor insertions, inferior view (left) and superior view (right.)


Tibialis posterior [1]

Origin: Interosseous membrane, posterior tibia, superior 60% of medial fibula
Insertion: Plantar surfaces of the navicular tuberosity, cuneiforms, cuboid and metatarsal base 2-4
Additional Actions: Plantar flexion and adduction at ankle joint

Flexor digitorum longus [2]

Origin: Posterior tibial shaft
Insertion: Plantar surfaces of distal phalanges 2-5
Additional Actions: Plantar flexion at ankle joint; flexion of digits 2-5 at distal interphalangeal joints

Flexor hallucis longus [3]

Origin: Distal 66% of posterior fibula and interosseous membrane
Insertion: Plantar distal phalange 1
Additional Actions: Plantar flexion at ankle joint; flexion of digit 1 at distal interphalangeal joint

Extensor hallucis longus [4]

Origin: Anterior fibula, adjacent interosseous membrane, beneath tibialis anterior
Insertion: Dorsal surface of distal phalange 1
Additional Actions:  Plantar flexion at ankle joint; extension of digit 1 at metatarsophalangeal and interphalangeal joints

Tibialis anterior [5]

Origin: Lateral tibial condyle and its proximal lateral shaft
Insertion: Medial surfaces of medial cuneiform and metatarsal base 1
Additional Actions: Plantar flexion at the ankle joint

References & Works Cited:

Barclay, T. 2018. “Anatomy Explorer,” innerbody.com. Accessed 19 Mar 2019. https://www.innerbody.com/anatomy/muscular/leg-foot.

Beckman, S. M., Buchanan, T. S. 1995. “Ankle inversion injury and hypermobility: Effect on hip and ankle muscle electromyography onset latency,” Archives of Physical Medicine and Rehabilitation 76; 12: 1138-1143. https://doi.org/10.1016/S0003-9993(95)80123-5.

Gray, H. 1918. “The Muscles and Fasciæ of the Lower Extremity,” Anatomy of the Human Body, 20th Ed. Lead & Febiger. Philadelphia & New York, USA.

Quinn, E. 2019. “Generally Accepted Values for Normal Range of Motion (ROM) in Joints,” verywellhealth.com. Accessed 19 Mar 2019. https://www.verywellhealth.com/what-is-normal-range-of-motion-in-a-joint-3120361.

Roaas, A., Andersson, G. B. J., 1982. “Normal Range of Motion of the Hip, Knee and Ankle Joints in Male Subjects, 30-40 Years of Age,” Acta Orthopaedica Scandinavica, 53:2, 205-208. https://www.tandfonline.com/doi/abs/10.3109/17453678208992202.

Visible Body. 2019. “Muscle Premium,” VisibleBody.com. Purchasable Application. Accessed 21 Feb 2019.

Washington State DSHS. 2014. “Range of Joint Motion Evaluation Chart,” Washington State Department of Social & Health Services. Accessed 20 Mar 2019. https://www.dshs.wa.gov/sites/default/files/FSA/forms/pdf/13-585a.pdf.


Kevin B. Rosenbloom, C.Ped, Sports Biomechanist

Kevin B. Rosenbloom, founder and president of Kevin Orthopedic, is a renowned certified pedorthist and sports biomechanist practicing in Santa Monica, CA. With his continuing research on the historical development of foot and ankle pathologies, comparative evolution of lower extremities and the modern environmental impacts on ambulation, he provides advanced biomechanical solutions for his patients and clients.

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