Anatomy, Bony Pelvis and Lower Limb, Calf Peroneus Longus Muscle

The peroneus longus muscle arises the head and upper lateral side of the fibula and inserts on the base of the first metatarsal, medial cuneiform. Its tendon passes inferior to the cuboid bone in a bone tunnel termed the cuboid tunnel and inserts onto the plantar surface of the foot on the medial cuneiform. However, several variants exist that may possess one or more accessory tendinous slips that insert into other neighboring bones or tendons. These physiologic variants are clinically important because the peroneus longus muscle is involved in several pathologies, including traumatic injury, tendinitis, dislocation, acute rupture, and chronic tear. Some of these may be more common with certain physiologic variants. A recent study described common physiologic variants in cadaveric specimens.[12] A table describing the incidence of various bony insertions of the peroneus longus tendon appears below.[12] The description of the most common insertions of the peroneus longus tendon may help physicians better understand the symptoms associated with peroneus longus tendon pathologies and the role played by the tendon in maintaining the arch of the foot.[12]

• The base of 1st metatarsal: 30 specimens, 100%
• Medial cuneiform: 26 specimens, 86.6%
• The neck of 1st metatarsal: 3 specimens, 10%
• The base of 2nd metatarsal: 6, 20%
• The base of 4th metatarsal: 5, 16.6%
• The base of 5th metatarsal: 7, 23.3%

In trauma and other mechanical injuries, the peroneus longus tendon can become dislocated, subluxated or ruptured. In 2016, a research team queried foot and ankle surgeons nationally to understand their management of acute peroneal tendon tears. There were marked differences in treatment protocols as well as operative techniques. 22% of the surgeons chose nonoperative treatment for greater than one year, while 33% immediately went to operative interventions. For surgeons who decided to operate, 88% tubularized tendons after the repair, 33% excised redundant tissue, and 22% removed the peroneal tubercle if it demonstrated hypertrophy.[13] In symptomatic patients, surgical treatment correlates with improved full return to activity and improvement in patient-reported outcome scores.[14] To optimize the recovery of surgically treated peroneal tendon tears and ruptures, a personalized, comprehensive rehabilitation program is necessary. Since most peroneal tendon tears occur in young active patients and athletes, early return to activity is of utmost importance.

The lateral compartment of the leg is also susceptible to acute compartment syndrome. When the pressure inside the lateral compartment increases, tissue perfusion can be compromised, which may lead to irreversible muscle and nerve damage, resulting in muscle and soft tissue necrosis.[5] The most common cause of compartment syndrome involving the lateral compartment is trauma, tight casts or dressing, post-ischemic swelling, and arterial injury.[5] However, it is also possible to develop compartment syndrome chronically and must merit consideration when a patient presents with lateral leg pain, tenderness, and firmness to palpation. Recognition of compartment syndrome is essential to the treatment and prevention of ischemia and necrosis of the neurovascular structures and muscles.[5][15][16][3] Patients with compartment syndrome will often present with pain out of proportion to the clinical situation. The physical exam findings of compartment syndrome often include pain on palpation of the muscles involved, pain with passive stretching of the muscle (most sensitive test finding before the onset of ischemia), and firmness of the compartment.[5] [15] [16] Compartment syndrome primarily affects the venous system. Consequently, arterial pulses are usually intact.[5] The definitive diagnosis of compartment syndrome requires measurement of compartmental pressures. A resting compartment pressure of greater than 30 mm Hg confirms the diagnosis of compartment syndrome.[5][15][16]  In acute compartment syndrome, time is of the essence—if treated within 6 hours of ischemia, complete recovery is anticipated whereas, after 6 hours of ischemia, necrosis occurs.[17] Definitive management of acute anterior compartment syndrome is subcutaneous fasciotomy.[5][15][16] 

The peroneus longus is important in plantar flexion and eversion of the foot at the ankle. For this reason, it is tested during the physical exam to assess the range of motion and motor strength of the ankle. Weakened or absent motor strength can indicate muscle or nerve damage to the peroneus longus and/or peroneus brevis muscles—the two muscles of the lateral compartment of the lower limb.[4] 

The peroneus longus muscle can also be involved in tendinitis, subluxation, dislocation, and acute or chronic tendon tears. Most peroneal tendon injuries occur in young, active patients, commonly occurring secondary to sports such as football, soccer, and running. Injury to the peroneus longus tendon is a cause of lateral ankle pain and may lead to ankle instability. Tears are most commonly longitudinal due to subluxation over the fibula but can also be transverse.[18] An isolated tear is more commonly found in the peroneus brevis muscle but can also occur in the peroneus longus. Non-operative treatment includes NSAIDs, ice, rest, immobilization, and physical therapy. Steroid injections can also be used in patient’s refractory to the treatments mentioned previously. Recent literature has shown a growing interest in PRP injections under ultrasound guidance; however, it is not commonly adopted in practice yet. If conservative treatment fails, operative treatment can include an open debridement and synovectomy and arthroscopic peroneal tendoscopy for tendinitis. For peroneal tendon tears, operative treatment includes an end to end repair, side-to-side anastomosis or Pulvertaft weave with chronic tears, as well as allograft reconstruction.[19][20]

Lastly, the lateral compartment of the leg can be involved in compartment syndrome. Although the anterior compartment is the most common site for compartment syndrome, lateral compartment syndrome can occur acutely following blunt force injury or trauma, or as a chronic, exertional syndrome commonly seen in athletes.[5][15] The muscle groups of the lower limb divide into compartments formed by strong, inflexible fascial membranes. Compartment syndrome occurs when increased pressure within one of these compartments’ compromises circulation and function to the tissues within that space.[5][15] The lateral compartment contains muscles that primarily plantar flexes the foot at the ankle and evert the foot. These muscles are innervated and supplied by the superficial peroneal nerve and anterior tibial artery, respectively. Increased pressure in the lateral compartment can cause paresthesias, weakness of muscle action, and pain with passive stretch of the muscles.[5][15] Compartment syndrome constitutes a medical emergency that requires fasciotomy of the involved compartment.[5]