The os tibiale externum, also known as the cuboid accessory navicular, is a secondary or accessory bone which is located close to the navicular bone in the foot. The presence of the os tibiale externum in the foot can vary from person to person and it is not present in all individuals. It can differ in size also and it can be fully developed in some people while it can be incomplete in others.
The os tibiale externum is associated with the tibialis posterior tendon, which is responsible for movement of the foot. The tendon helps keep the arch of the foot up and helps maintain the foot position. Bourne et al. ( 2018) found that the accessory bone helps to support and increase the integrity of the tendon. This bone helps the foot to spring off the ground while walking or running. In return, this helps to increase the functionality of the tendon. Thus, the presence of the healthy and complete os tibiale externum has been found to contribute positively to the foot biomechanics thereby facilitating the movement and hence the balance.
The os tibiale externum is a bony spur that is particularly relevant in the field of sports medicine and rehabilitation. As a result of its unique location in the foot, it is a structure that athletes – especially dancers – should be aware of. Many dance positions require the foot to be highly flexible and strong, and an abnormally formed or positioned os tibiale externum can exacerbate stress on the foot, potentially leading to conditions such as tendonitis or stress fractures. As stated by Rietveld and Diemer (2016), an understanding of the os tibiale externum can lead to a more effective treatment plan. Yamajala and Mane (2023) also believe that the assessments for the rehabilitation of injuries should include the position of the os tibiale externum in order to prevent further injury and to aid in the rehabilitation of the injury.
The os tibiale externum can affect movement and functionality as well as several disease patterns. As a rule the os tibiale externum is associated with pain phenomena related to foot functionality. Often, pain in the foot area occurs due to inflammation of ligaments or due to inflammation within the body itself. A study by Kroker and Rammelt from 2020 illustrates, among other things, that the accessory bone in the foot can also play a role in posterior tibial tendon dysfunction and can thereby burden other problems in the foot. A deviation in foot functionality through diseased areas leads to a functional compensation that moves up the kinetic chain to e.g. the knee or hip.
The os tibiale externum has been described as an important component of foot structure and function. Understanding the role that the os tibiale externum plays in movement mechanics is important for the recognition of conditions that affect athletic performance, especially when treating sports injuries such as those sustained by dancers. In fact, an awareness of the clinical implications of the os tibiale externum and the possible clinical conditions associated with the structure can positively impact the diagnostic and treatment processes in a variety of clinical and sports settings. The accessory navicular is known also as the os tibiale externum. It is a small additional bone on the medial aspect of the foot, near the junction with the lower end of the tibia. Its presence and effects are significant for individuals with active lifestyles who may have specific biomechanical foot disorders.
The most common condition to be associated with the os tibiale externum is accessory navicular syndrome. The bone can become painful and swollen due to the chronic and repeated irritation of the soft tissues and overloading of the bony growth. According to some literature studies made by Golano et al. ( 2004) and Haumont et al. ( 2007), the majority of patients that have the accessory navicular syndrome complain of pain at the location of the extra bone during athletic activities such as running and jumping, hence the need for a more extreme treatment such as surgery to remove the bone of the os tibiale externum. Most often this is required after the patient has exhausted the other treatments, that generally start with rest, application of ice to the area and physical therapy.
The os tibiale externum was first mentioned by Cruveilhier in 1829, and in recent years a larger number of articles have discussed the influence of its presence on foot biomechanics. Vieira et al. (2025) verified that its presence alters foot mechanics during walking and running. Petersen & Tillmann (2002) stated that its presence results in greater loads in other structures of the foot and ankle and is an aetiological factor in musculotendinous injuries such as strains or sprains.
Diagnosis of os tibiale externum problems usually involves examination of the foot along with X-rays or an MRI scan to determine if the accessory bone is the cause of the patient’s problems and the extent of its involvement. Treatments can range from conservative to surgical. Moriggl et al. ( 2003) point out that a correct shoe fit, along with foot, ankle, and leg stretching and strengthening is often recommended as a preventive measure. This is especially important to those engaged in athletic activities such as running. An accessory navicular syndrome can also be a related problem to os tibiale externum problems.
Understanding the Os Tibiale Externum (OTE) is important for diagnosis and for providing appropriate care and management that will help to achieve a good outcome for the patient. This accessory bone needs to be considered when carrying out treatments to address any issues that arise and to prevent further problems arising. A thorough understanding of any variations in the foot that may arise and how the OTE affects these and in turn the function of the foot is also important. Further studies of the OTE and how it affects the foot and foot function and any conditions that may arise will be important to further our understanding of the foot and the possible causes of any problems that may arise. So it is important to note the OTE and its dimensions.
Citations:
Bourne, M., Sinkler, M.A. and Murphy, P.B., 2018. Anatomy, bony pelvis and lower limb, tibia. https://europepmc.org/books/nbk526053
Vieira, E.L.C. and Gali, J.C., 2025. Functional Anatomy of the Extra-articular Structures of the Knee: The Lateral Side. In Sports Injuries: Prevention, Diagnosis, Treatment and Rehabilitation (pp. 1747-1759). Cham: Springer Nature Switzerland. https://link.springer.com/content/pdf/10.1007/978-3-031-58351-3_415.pdf
Vieira, E.L.C., Vieira, E.Á., Da Silva, R.T., dos Santos Berlfein, P.A., Abdalla, R.J. and Cohen, M., 2007. An anatomic study of the iliotibial tract. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 23(3), pp.269-274. https://www.sciencedirect.com/science/article/pii/S0749806306014435
Haumont, T., Gauchard, G.C., Zabee, L., Arnoux, J.M., Journeau, P. and Lascombes, P., 2007. Extensor retinaculum syndrome after distal tibial fractures: anatomical basis. Surgical and Radiologic Anatomy, 29(4), pp.303-311. https://link.springer.com/article/10.1007/s00276-007-0215-3
Petersen, W. and Tillmann, B., 2002. Anatomy and function of the anterior cruciate ligament. Der Orthopade, 31(8), pp.710-718. https://europepmc.org/article/med/12426749
Yamajala, S. and Mane, S.S., 2023. Beyond the obvious: Exploring Os Tibiale Externum and Os Peroneum in Foot and Ankle Pain-A Case Series. Journal of Orthopaedic Case Reports, 13(3), p.44. https://pmc.ncbi.nlm.nih.gov/articles/PMC10178825/
Rietveld, A.B.M. and Diemer, W.M., 2016. Surgical treatment of the accessory navicular (os tibiale externum) in dancers: a retrospective case series. Journal of Dance Medicine & Science, 20(3), pp.103-108. https://journals.sagepub.com/doi/abs/10.12678/1089-313X.20.3.103
Kroker, L. and Rammelt, S., 2020. Bipartite os tibiale externum: A rare condition causing foot pain. Fuß & Sprunggelenk, 18(3), pp.227-233. https://www.sciencedirect.com/science/article/pii/S1619998720300775
Golano, P., Fariñas, O. and Sáenz, I., 2004. The anatomy of the navicular and periarticular structures. Foot and ankle clinics, 9(1), pp.1-23. https://www.foot.theclinics.com/article/S1083-7515(03)00155-4/abstract
Moriggl, B., Kumai, T., Milz, S. and Benjamin, M., 2003. The structure and histopathology of the enthesis organ at the navicular insertion of the tendon of tibialis posterior. The Journal of rheumatology, 30(3), pp.508-517. https://www.jrheum.org/content/30/3/508.short
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