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The peroneus quartus (PQ) is an accessory muscle of the peroneal/lateral compartment of the leg. It is a supernumerary muscle of the lateral compartment of the lower leg. The peroneus quartus is found in 10 to 21.7% of observed individuals. It is rarely involved in pathological processes of the foot and ankle. The frequent occurrence of this muscle in humans is suggestive of a progressive evolutionary change to evert the foot in order to assume a bipedal gait.
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What You'll Learn
Peroneus Quartus Muscle and Evolutionary Change
The peroneus quartus (PQ) is an accessory muscle of the peroneal/lateral compartment of the leg. It is a supernumerary muscle, meaning that it is additional to the essential muscles required for movement. The peroneus quartus is found in 10 to 21.7% of individuals, with one study finding it in 21% of cadaver legs and another finding it in 5.2%.
The muscle has been associated with pain in the lateral ankle region and subluxation or attrition of the peroneal tendons. It is rarely involved in pathological processes of the foot and ankle, but when it is, it can be used to reconstruct some pathological conditions.
The peroneus quartus has a variety of different names and presentations, which has led to confusing terminology. It has been suggested that the frequent occurrence of this muscle in humans is indicative of an evolutionary change to evert the foot and assume a bipedal gait. This idea is supported by the fact that the muscle is rarely found in other primates.
The peroneus quartus is an accessory muscle to the peroneus brevis, with which it shares a tendon. The peroneus brevis is involved in plantar flexion and eversion of the foot, and the peroneus quartus may assist with these movements. The peroneus quartus may also help to stabilise the foot and ankle during gait.
The muscle has clinical importance, particularly in the field of orthopaedics. It can be used as a tendon graft for reconstructive procedures in the ankle. It is important for orthopaedists, anatomists, and radiologists to be aware of the peroneus quartus and its potential implications for ankle pathology.
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Peroneus Quartus and Ankle Pathology
The peroneus quartus (PQ) is a supernumerary muscle of the lateral compartment of the lower leg. It is a rare accessory muscle, found in only 10 to 21.7% of individuals. It is often asymptomatic, but it can be implicated as a cause of pain in the lateral ankle region, tendon subluxation, and attrition of the peroneal tendons. The peroneus quartus is associated with a range of pathologies, including retromalleolar conflict, longitudinal attrition, and tears of the peroneus brevis. It can also result in imaging pitfalls, as its accessory tendon can be mistaken for a tear.
The peroneus quartus has been identified as a potential etiology of ankle pain and tendon subluxation. In one case, a 16-year-old boy presented with lateral right ankle pain and subluxation of the peroneal tendons. Imaging revealed a split peroneus brevis tendon, and during surgery, a PQ muscle was found and excised, resolving the patient's symptoms. In another case, a 47-year-old male long-distance runner experienced longstanding pain in his left calf, which was diagnosed as a chronic peroneal compartment syndrome. An endoscopic-assisted fasciotomy of the peroneal compartment resolved his symptoms.
The peroneus quartus is also associated with functional ankle instability. It can play a role in the development of pain, swelling, and functional impairment of the ankle joint. Treatment options for pathology related to the peroneus quartus include fasciotomy or complete excision of the muscle. In some cases, the peroneus quartus can be used in ankle surgery to repair retinaculum injuries.
The presence of the peroneus quartus may be a result of evolutionary change, suggesting that it may have played a role in everting the foot to assume a bipedal gait. It is important for surgeons, radiologists, and clinicians to be aware of variant muscles like the peroneus quartus when considering diagnoses, interpreting radiographs, and planning surgical interventions for lateral ankle pathologies.
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Peroneus Quartus and Ankle Pain
The peroneus quartus (PQ) is an accessory muscle of the peroneal/lateral compartment of the lower leg. It is a supernumerary muscle, meaning that it is additional to the standard complement of muscles. The peroneus quartus is found in 10 to 21.7% of individuals, and it is rarely involved in pathological processes of the foot and ankle. However, it has been implicated as a cause of pain in the lateral ankle region, as well as subluxation or attrition of the peroneal tendons.
The peroneus quartus muscle has been shown to cause lateral ankle pain, ankle instability, fibular tenosynovitis, subluxation of the fibular tendons, and longitudinal splitting of the fibularis brevis tendon. This muscle can also lead to overcrowding in the peroneal sheath, reducing the available space for the peroneal muscles and potentially contributing to instability. The presence of the peroneus quartus muscle can be confirmed through magnetic resonance imaging (MRI) or surgery, and treatment options include fasciotomy or complete excision of the muscle.
There are several reported cases of individuals experiencing ankle pain associated with the peroneus quartus muscle. One case involved a 16-year-old boy who presented with lateral right ankle pain and subluxation of the peroneal tendons. Another case described a 47-year-old male long-distance runner with longstanding pain in his left calf, which was diagnosed as a chronic peroneal compartment syndrome. In both cases, surgical intervention, including fasciotomy or excision of the peroneus quartus muscle, resolved the patients' symptoms.
The peroneus quartus muscle is often asymptomatic, and its presence may go unnoticed. However, in some cases, it can contribute to chronic ankle pain and instability, particularly when there is weakness in the peroneus brevis and longus muscles. Conservative treatments for ankle instability may not always be effective in the presence of the peroneus quartus muscle, and surgical exploration and resection may be necessary for symptom relief.
In summary, the peroneus quartus muscle is a rare but potential cause of ankle pain and instability. It is important to consider the presence of this muscle in patients presenting with lateral ankle pain or functional ankle instability, especially when other treatments have failed. Treatment options such as fasciotomy or surgical excision of the muscle can provide effective relief from symptoms.
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Peroneus Quartus and Ankle Instability
The peroneus quartus is an accessory muscle of the peroneal/lateral compartment of the lower leg. It is rarely involved in pathological processes of the foot and ankle. The peroneus quartus is found in 10% to 21.7% of observed individuals, and most times this muscle is asymptomatic. However, some cases of chronic ankle pain or instability have been reported. The muscle has often been implicated as a cause of pain in the lateral ankle region, and subluxation or attrition of the peroneal tendons.
Several anatomical muscle-tendon variations have been described in the literature as being sometimes responsible for ankle instability, with the peroneus quartus muscle being the most frequent. The peroneus quartus muscle should be considered in the differential diagnosis of chronic lateral ankle pain. It is important to note that the terminology surrounding the peroneus quartus is very confusing.
A clinical study discusses the implication of the bilateral peroneus quartus muscle in functional ankle instability. The patient, a 26-year-old, was seen in consultation for recurrent episodes of lateral ankle sprains. The clinical examination found a moderate hyperlaxity on the right side in bilateral ankle varus, as well as bilateral weakness of the peroneus muscles. Additional imaging examinations showed a supernumerary bilateral peroneus quartus.
One hypothesis for the cause of ankle instability is the overcrowding effect, which results in a true conflict by reducing the available space for the peroneal muscles in the peroneal sheath.
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Peroneus Quartus and Accessory Muscles
The peroneus quartus (PQ) is an accessory muscle of the peroneal/lateral compartment of the leg. It is a supernumerary muscle, meaning that it is additional to the standard number of muscles in the leg. The peroneus quartus arises from the peroneus brevis muscle and courses medial and posterior to the peroneus longus and peroneus brevis muscles and tendons before inserting onto the lateral hind and midfoot.
The origin of the PQ muscle is the distal lateral portion of the fibula, and it typically descends medial and posterior to the peroneal tendons. The PQ muscle is usually asymptomatic, but it can occasionally lead to crowding in the retromalleolar groove, which can cause peroneus brevis tendon attrition and tears. The muscle has often been implicated as a cause of pain in the lateral ankle region, and subluxation or attrition of the peroneal tendons.
The peroneus quartus is found in 10% to 21.7% of observed individuals, with a true accessory peroneal muscle prevalence of 16%. It is rarely involved in pathologic processes of the foot and ankle, but when it is, it can cause pain, swelling, ankle instability, subluxations, mechanical attrition, longitudinal tears, and tenosynovitis of the peroneal tendons. Symptomatic relief has been reported with surgical excision.
The frequent occurrence of this muscle in humans suggests that it is a result of progressive evolutionary change to evert the foot in order to assume a bipedal gait. The terminology used to describe the peroneus quartus and its variations is very confusing, with several different terms used to refer to the same muscle.
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Frequently asked questions
The peroneus quartus (PQ) is an accessory muscle of the peroneal/lateral compartment of the leg. It is a supernumerary muscle of the lateral compartment of the lower leg.
The peroneus quartus muscle is found in 10-21.7% of observed individuals. However, another study found it to be present in only 6.6% of the legs examined.
The origin of the PQ muscle is the distal lateral portion of the fibula. It usually descends medial and posterior to the peroneal tendons.
The peroneus quartus muscle has been implicated as a cause of pain in the lateral ankle region. It has also been associated with subluxation or attrition of the peroneal tendons.
