Posterior Malleolus: Anatomy & Fracture
The posterior malleolus is the bony projection at the back of the shinbone. It forms part of the ankle joint and can be fractured in ankle injuries.
Things worth knowing about "Posterior Malleolus"
The posterior malleolus is the bony projection at the back of the shinbone. It forms part of the ankle joint and can be fractured in ankle injuries.
What is the Posterior Malleolus?
The posterior malleolus (Latin: malleolus posterior) is a bony prominence located at the posterior (back) aspect of the tibia (shinbone). Together with the medial malleolus (inner ankle, also part of the tibia) and the lateral malleolus (outer ankle, part of the fibula), it forms the ankle mortise – the socket-like structure that encompasses the talus bone and forms the upper ankle joint (articulatio talocruralis).
The upper ankle joint is a hinge joint that enables the foot to move upward (dorsiflexion) and downward (plantarflexion). The posterior malleolus provides the posterior boundary of the joint socket and plays a critical role in maintaining ankle stability.
Anatomical Significance
The posterior malleolus is anatomically important because it:
- forms part of the posterior articular surface of the ankle joint,
- serves as an attachment site for important ligaments and tendons,
- prevents posterior displacement of the talus,
- contributes to the overall stability of the upper ankle joint together with the other malleoli.
The posterior surface of the malleolus also provides a groove for important tendons running toward the sole of the foot, including the tendons of the flexor digitorum longus and tibialis posterior muscles.
Injuries of the Posterior Malleolus
Injuries to the posterior malleolus most commonly occur as part of ankle fractures. A particularly well-known injury pattern is the trimalleolar fracture (also called a three-malleolus fracture), in which all three malleoli are broken simultaneously. Isolated fractures of the posterior malleolus are less common but do occur.
Causes and Mechanisms
Fractures of the posterior malleolus typically result from:
- Twisting injuries of the ankle, such as during sports or a fall,
- Rotational trauma, where the foot rotates while the leg remains fixed,
- Axial loading injuries caused by falling from a height,
- Motor vehicle accidents and other high-energy trauma.
Symptoms
Typical symptoms of a posterior malleolus fracture include:
- severe pain around the ankle and posterior lower leg,
- swelling and bruising (hematoma) around the ankle,
- tenderness on palpation over the posterior tibial margin,
- restricted range of motion of the ankle joint,
- inability to bear weight on the affected foot.
Diagnosis
Diagnosis of a posterior malleolus fracture is established through:
- X-rays of the ankle in two planes (anteroposterior and lateral) as the initial imaging study,
- Computed tomography (CT): Provides detailed assessment of fragment size, joint involvement, and displacement; essential for surgical planning,
- Magnetic resonance imaging (MRI): Indicated when additional ligament or cartilage damage is suspected.
A key factor in clinical decision-making is the size of the posterior fragment: if the fragment involves more than 25–30% of the articular surface, surgical fixation is generally recommended to maintain joint stability and congruency.
Treatment
Conservative Treatment
Small, non-displaced or minimally displaced fractures of the posterior malleolus involving less than 25% of the joint surface can often be treated conservatively. This includes:
- immobilization in a below-knee cast or a supportive boot for 6 to 8 weeks,
- non-weight-bearing on the affected leg using crutches,
- anti-inflammatory and pain-relieving medications (e.g., ibuprofen, diclofenac),
- subsequent physiotherapy to restore range of motion and muscle strength.
Surgical Treatment
Larger or displaced fragments require surgical management. Common procedures include:
- Screw fixation (osteosynthesis): The bony fragment is secured with metal screws inserted from front to back or from back to front,
- Plate fixation: A metal plate is used for additional stabilization in complex fracture patterns,
- simultaneous repair of frequently associated medial and lateral malleolus fractures.
Rehabilitation and Recovery
Recovery following a posterior malleolus fracture can take several months depending on injury severity and treatment method. Structured physiotherapy is essential to restore full ankle function. Rehabilitation goals include recovery of range of motion, muscle strength, and proprioceptive (balance-related) function.
If not adequately treated, long-term complications such as post-traumatic ankle osteoarthritis may develop. Therefore, proper medical treatment and follow-up care are of particular importance.
References
- Browner BD, Jupiter JB, Krettek C, Anderson PA: Skeletal Trauma: Basic Science, Management, and Reconstruction. 5th edition. Elsevier Saunders, 2015.
- Haraguchi N et al.: Pathogenesis of posterior malleolus fractures of the ankle. Journal of Bone and Joint Surgery, 2006; 88(5): 1085–1092. DOI: 10.2106/JBJS.E.00856.
- Court-Brown CM, McBirnie J, Wilson G: Adult ankle fractures – an increasing problem? Acta Orthopaedica Scandinavica, 1998; 69(1): 43–47. DOI: 10.3109/17453679809002355.
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