The anterior tibial tendon originates along the anterolateral tibia and inserts onto the medial aspect of the first metatarsal and medial cuneiform. It functions concentrically during the swing phase of gait to dorsiflex the ankle and allow clearance of the foot. At heel strike, the tendon works in an eccentric fashion to control the progression to the foot’s flat position. The anterior tibial tendon also assists with inversion of the foot.

Rupture of the anterior tibial tendon is relatively uncommon, and most studies involved only a small number of patients.^1,2 A normal anterior tibial tendon rarely ruptures except as a result of a laceration or sudden force. Spontaneous rupture occurs secondary to a degenerative process, usually in men aged 50 to 70 years.¹ The causes of degeneration include impingement, inflammatory arthritis, diabetes mellitus, infection, chronic microtrauma, ischemia, hyperparathyroidism, systemic lupus erythematosus, gout, obesity, and oral or local steroid therapy.³ The usual site of an anterior tibial tendon rupture is 0.5 to 3 cm proximal to its insertion, where the tendon passes under the inferior extensor retinaculum. Formerly this location was believed to be a vascular watershed area within the tendon, but microvascular studies have not found such an area.⁴

Anterior tibial tendon rupture appears in two forms. In relatively young patients, an acute onset of symptoms occurs after penetrating injury or severe trauma; in patients older than 50 years, a moderately forceful plantar flexion stress can bring on the symptoms. The second form is seen in relatively sedentary patients older than 50 years with a several-month history of atraumatic foot drop. The rupture may have a prodrome of swelling, or it may follow a minor misstep or a twisting injury of the ankle. The signs and symptoms of the second form of anterior tibial tendon injury can be confusing.¹ The injury may be masked by a rapid resolution of any initial pain and compensation by the other extensor muscles. As a result, the diagnosis of rupture often is missed or delayed.³ Pain may be minimal after the initial episode and is not a major factor for many patients who seek treatment. A patient is likely to report a foot slap or unsteady gait, limping, or increased fatigue with walking. Some patients may experience persistent anterior ankle pain as the extensor tendons compensate for decreased dorsiflexion strength.

Physical examination findings include gait abnormalities such as a foot slap or foot drop. It may be possible to palpate the proximal stump of the anterior tibial tendon as a mass along the anteromedial aspect of the ankle. Dorsiflexion of the ankle reveals eversion of the foot and a loss of tendon contour compared with the contralateral limb. Most patients are able to use the remaining, functioning tendons for dorsiflexion, but careful testing will reveal a strength deficit in comparison with the contralateral limb. Increased extension at the metatarsophalangeal joint of the toes may be observed as the extensor tendons attempt to compensate for loss of dorsiflexion power.

Both surgical and nonsurgical treatments have been recommended, but the optimal treatment remains controversial. One study found no difference in outcomes after surgical or nonsurgical treatment.⁵ The patients treated nonsurgically had an average age of 74 years and had low physical demands; most of the patients treated surgically had an average age of 55 years and were more physically
active. No relevant randomized prospective studies have been published. The available research is primarily composed of case reports and small studies, most of which recommended early direct repair to restore function.^5,6,7 This procedure may be particularly beneficial for a relatively young, active patient with a traumatic injury to the tendon. Direct tendon repair may be possible within the first few months after injury.³ The retracted tendon end usually becomes entrapped at the distal extent of the superior extensor retinaculum.^2,6 Direct repair can be done end to end with a grasping stitch using a Krackow, Kessler, or Bunnell technique. If the tendon is avulsed off the insertion site, suture anchors or soft-tissue interference screws can be used for reattachment.

Late treatment after an atraumatic rupture should be individualized based on the patient’s activity level. A patient with low physical demands or a significant medical comorbidity may benefit from nonsurgical treatment. The use of an ankle-foot orthosis can facilitate foot clearance during the swing phase of gait and decrease fatigue during prolonged ambulation. Some patients find brace treatment overly restrictive and opt not to use it.³ In a delayed surgical procedure, end-to-end repair may not be feasible because of adhesions and lack of excursion of the tendon ends, and an interpositional graft is likely necessary. A variety of methods have been described for treating chronic ruptures, including Achilles tendon grafting or transfer of the extensor hallucis longus, extensor digitorum longus, plantaris, or peroneus tertius tendon.^2,3,6,7

A 2009 retrospective review evaluated the results of surgical treatment of 19 anterior tibial tendon ruptures in 18 patients.⁶ Eight tendons had an early repair, and 11 had a delayed repair; 7 were treated with a direct repair, and 12 required the use of an interpositional graft. The plantaris tertius tendon was most commonly used for grafting, followed by the extensor digitorum longus tendon. Patients in both the early repair group and the late repair group had significant improvement in scores on the American Orthopaedic Foot and Ankle Society (AOFAS) measure. Manual testing revealed normal dorsiflexion strength in 15 of the 19 ankles. Tendon repair was recommended for all patients with an unsteady gait, weakness, or fatigability because of lack of dorsiflexion strength. A 2010 retrospective review of 15 surgically treated anterior tibial tendon ruptures in 14 patients found significant improvement in postoperative AOFAS and Medical Outcomes Study 36-Item Short Form scores.⁷ Five tendons were repaired primarily, and 10 had a tendon transfer; 9 of the transfers used the extensor hallucis longus tendon. There was no difference in the outcomes of patients with a primary repair and those who required a tendon transfer. Strength testing using a dynamometer and comparison with the uninjured contralateral limb found deficits in dorsiflexion strength in all patients. A 2015 retrospective study of 11 patients with chronic anterior tibial tendon ruptures evaluated the use of allograft in those with greater than a 4 cm gap between tendon ends.⁸ Significant improvements in strength, VAS (Visual Analog Scale) pain score, and functional outcome scores were noted. The authors felt allografts offered the advantages of shorter surgical times, absence of donor site complications, and greater options in regard to size and types of grafts.

No randomized prospective studies are available to guide the treatment of anterior tibial tendon ruptures; only case reports and relatively small retrospective case studies have been published. Patients with an atraumatic injury who have low physical demands and seek treatment after a delay can be treated nonsurgically, but most researchers favor surgical treatment of patients who have relatively high physical demands.^2,3,5,6,7 In patients undergoing late treatment, an interpositional graft usually is required.

The peroneal tendons originate as muscle bellies in the lateral compartment of the leg and become tendinous as they pass through a fibro-osseous tunnel posterior to the lateral malleolus. The peroneal tendons share a sheath that bifurcates at the level of the peroneal tubercle of the lateral calcaneus. The peroneus longus runs posterolateral to the peroneus brevis and turns sharply at the tip of the fibula, passing under the trochlear process of the calcaneus and along a groove in the plantar surface of the cuboid to insert on the plantar base of the first metatarsal. The peroneus brevis muscle belly is lower and lies between the posterior fibula and the peroneus longus tendon in the fibro-osseous tunnel before turning under the tip of the fibula to insert on the fifth metatarsal base. The peroneal tendons function as the major evertors and pronators of the ankle. In addition, the peroneus longus plantar flexes the first metatarsal.

A typical peroneal tendon disorder is classified as peroneal tendinitis without subluxation of the tendons, peroneal tendinitis with subluxation of the peroneal tendons at the level of the superior retinaculum, or stenosing tenosynovitis of the peroneus longus in the area of the peroneal tubercle, os peroneum, or cuboid tunnel. Peroneal tendon injuries can be missed because they often occur in conjunction with a lateral ankle sprain, with only vague symptoms along the lateral ankle.⁹ A patient with an acute injury may report having twisted the ankle. Symptoms of subluxation often can be concealed by the pain and swelling associated with a lateral ankle sprain.
Swelling posterior to the lateral malleolus occurs with peroneal instability, tearing, and synovitis. Symptoms of tenosynovitis can be brought on by a change in activity level. A patient with a dislocation often reports pain and a popping sensation along the lateral retromalleolar area.

A careful physical examination often is the most important step in making the appropriate diagnosis. Acute subluxation may present with ecchymosis posterior to the lateral malleolus, and it may be associated with tenderness over the insertion of the superior retinaculum. Pain and a sensation of instability in the lateral retromalleolar area can be reproduced with active eversion and dorsiflexion of the ankle.¹⁰ Palpable snapping or crepitus may be evident during this maneuver. Synovitic thickening appears to be the most reliable sign of a peroneal tendon tear.¹¹ Pain with forced plantar flexion and inversion may be seen with synovitis. Pain is not always present with a peroneal tendon tear, but it may be possible to elicit pain with resisted eversion. A tear may cause tenderness along the course of the tendon. A longitudinal tear can cause early fatigability without apparent weakness.¹² A peroneus longus tear can cause pain with resisted plantar flexion of the first metatarsal. A patient with suspected peroneal tendon pathology should undergo an assessment for concomitant ankle instability and evaluation of the alignment of the hindfoot. Varus alignment may be seen with long-standing peroneal tendon pathology or may be a precursor to it. An excessively valgus hindfoot may cause subfibular impingement as the tendons are compressed between the tip of the fibula and the calcaneus.

A plain radiograph may reveal an avulsion fracture of the lateral aspect of the distal fibula and suggest a peroneal tendon subluxation. Hypertrophy of the peroneal tubercle suggests peroneal tendon impingement. Fracture or migration of the os peroneum proximal to the calcaneocuboid joint may indicate a peroneus longus tear. The role of MRI in the evaluation of peroneal tendon pathology is unclear. A normal peroneus brevis tendon can appear to be partially torn because of an increase in signal intensity on T1-weighted images (the so-called magic angle effect). Tendon subluxation may be difficult to detect on magnetic resonance scan, especially if the subluxation is intermittent. A study of magnetic resonance images in 133 patients found that radiologists detected only 56% of the peroneus brevis tears present at surgery.¹³ In 82 patients who underwent surgery for lateral ankle instability, the positive predictive value of MRI for peroneal tendons was 66.7%.¹⁴ Overreliance on MRI was found to lead to unnecessary surgical procedures. A retrospective review of 294 magnetic resonance images in individuals without any lateral ankle symptoms found that 35% of the studies were interpreted as having some peroneal tendon pathology.¹⁵

Acute peroneal tendon dislocation usually is associated with a traumatic event during a sports activity involving rapid changes in direction. The mechanism of injury is somewhat controversial; both inversion and extreme dorsiflexion have been suggested as the ankle position at the time of injury. An eccentric contraction of the peroneal tendons against resistance causes avulsion of the superior peroneal retinaculum off the fibula, often with periosteum or a cortical bone fragment off the lateral aspect of the fibula. The periosteum is elevated, creating a pouch in which the dislocated tendons sit.

The onset of chronic peroneal tendon subluxation usually is insidious and occurs after an untreated acute dislocation.¹⁰ Recurrent subluxation from behind the lateral malleolus attenuates the superior retinaculum and often is associated with a split tear of the peroneus brevis tendon as it is caught between the fibrocartilaginous rim and the peroneus longus tendon. Often there is associated tenosynovitis.

Acute peroneal tendon dislocation that spontaneously reduces can be treated with immobilization. The reported success rate of nonsurgical treatment is approximately 50%.¹⁶ Relatively young patients with high physical demands are treated surgically. Recurrent subluxation of the peroneal tendons can be associated with longitudinal tearing in the peroneus brevis, which should be treated during the instability surgery. Surgical treatment options for peroneal tendon subluxation include reconstruction of the superior peroneal retinaculum, rerouting of the tendons under the calcaneofibular ligament, reconstruction of the retinaculum with a portion of the Achilles tendon, and a groove-deepening procedure. An isolated repair or reconstruction of the retinaculum is ideal for an acute dislocation in which the tissue is unlikely to be compromised.¹⁶ In chronic dislocation, compromised retinacular tissue may require augmentation of the retinaculum with additional tissue or routing of the tendon under the calcaneofibular ligament.

The retromalleolar groove, in which the tendons rest, usually is concave, but it is flat or convex in 10% to 20% of patients.¹⁷ The flat or convex shape contributes to peroneal tendon instability, and a groove-deepening procedure is considered if the patient has a flat or convex configuration of the posterior fibula. The extent of impaction or deepening is adjusted until it is sufficient to prevent dislocation of the tendons with ankle manipulation. A variety of techniques have been described. A recent technique uses tendoscopy to deepen the groove.¹⁰ Seven patients with peroneal dislocation had the retromalleolar groove deepened with a burr and tendoscopy. Four patients had detachment of the superior retinaculum at the site of the
fibular insertion, but surgical repair was not attempted. At an average 15.4-month follow-up, none of the patients had recurrent subluxation, and five reported an excellent outcome. Although the procedure was claimed to lead to less morbidity and more rapid recovery than an open procedure, the study included no control group for comparison.

Recent research has questioned the association between groove morphology and peroneal subluxation.^17,18,19 A retrospective MRI study of 39 ankles after surgical treatment of peroneal tendon dislocation classified the shape of the retromalleolar groove as concave, convex, or flat.¹⁹ No significant difference was found on magnetic resonance images between the treated ankles and 39 ankles without peroneal tendon dislocation. The superior peroneal retinaculum inserts into a fibrocartilaginous rim on the posterolateral fibula, which helps to deepen the retromalleolar groove, and the study authors suggested that this rim has a significant role in stabilizing the tendons. A cadaver study found that the peroneal tunnel has two components: an osseous component is formed by the retromalleolar groove, and a medial soft-tissue component is formed by the posterior intermuscular septum of the leg¹⁸ (Figure 1). The study concluded that the retromalleolar groove is shallow and unable to accommodate the peroneal tendons and suggested that splitting the soft-tissue component may be as effective as groove deepening. A 2014 study prospectively compared peroneal tendon stabilization with and without fibular groove deepening. It was a consecutive series of 29 patients where 13 patients had groove deepening and 16 did not. The author found no significant difference in outcome between the two groups and noted those without groove deepening had significantly decreased surgical time and the procedure was easier.²⁰ A 2016 healthcare database reviewed concluded that soft-tissue procedures offer a satisfactory method of treating peroneal tendon dislocation without increased risk of revision surgery when compared with osteotomy techniques.²¹

Peroneal tenosynovitis, also called peritendinitis, usually results from repetitive or prolonged activity or from trauma to the peroneal tendons. Peroneal tenosynovitis may be the result of stenosis of the synovial sheath, which can occur in the presence of a hypertrophied peroneal tubercle or other anatomic factors such a cavovarus foot, osseous calcaneal tunnel, presence of a peroneus quadratus muscle, and an incompetent superior peroneal retinaculum. Tenosynovitis usually occurs at a location where the tendon changes direction, such as behind the lateral malleolus, at the trochlear process, or under the cuboid. Tenosynovitis can be exacerbated by the presence of a space-occupying structure such as a low-lying peroneus brevis muscle belly or peroneus quartus tendon.

The initial treatment often is nonsurgical and may include activity modification, NSAIDs, physical therapy, a lateral-wedge orthotic device, or an ankle brace. If the condition does not improve, short-term immobilization with a boot or a short leg cast can be considered. Nonsurgical management is effective in most patients, but surgical treatment may be indicated if nonsurgical treatment is unsuccessful. Surgical treatment involves débridement of inflamed tenosynovium, release of any areas of stenosis or compression around the tendon, removal of any space-occupying structures such as a low-lying peroneus brevis muscle belly or peroneus quartus tendon, and repair or débridement of pathologic tendon. In addition, any associated ankle or tendon instability or hindfoot malalignment should be corrected.

Peroneal tendon tears may be associated with chronic ankle instability, peroneal tendon subluxation or dislocation, cavovarus hindfoot, a prominent peroneal tubercle, or an accessory tendon. These tears are believed to be caused by acute or repetitive mechanical trauma. Peroneus
brevis tears are reported to be more common than peroneus longus tears.⁹ Peroneus brevis tears most often occur at the distal portion of the lateral malleolus, where the peroneus longus tendon compresses the peroneus brevis tendon against the lateral malleolus.¹⁶

In the absence of an acute rupture, usually the treatment is nonsurgical and of 2 to 6 months’ duration.¹² If surgical treatment is indicated, it is important to recognize that peroneal tendon injuries can be associated with other injuries. All 30 patients who had arthroscopic evaluation of the ankle at the same time as peroneal tendon repair were found to have intra-articular pathology.⁹ Extensive scar tissue was the most common diagnosis, followed by synovitis and soft-tissue impingement. The absence of a comparison group in this study makes it difficult to determine the true benefit of arthroscopy.

Peroneal tendon tears typically are longitudinal rather than transverse, although transverse tears can occur.¹¹ The low-lying muscle belly of the peroneus brevis has been implicated as a contributor to peroneal tendon tears. A study of 115 cadaver specimens found that peroneus brevis tears were more common if the peroneus musculotendinous junction was relatively proximal.²² The traditional recommendation is for débridement and tubularization of tears involving less than 50% of the tendon diameter and for débridement and tenodesis of larger tears.¹¹ A 2014 retrospective study of 18 patients who underwent débridement and primary repair reported that 17 patients returned to full sporting activity without limitations.²³ A 2016 retrospective study of 71 patients who underwent primary repair of the peroneus brevis tears showed that 83% were able to return to regular exercise and sports at final follow-up and 91% would undergo the same procedure again.²⁴ If one of the peroneal tendons has tears involving greater than 50% of the diameter and the other is relatively intact, then débridement of the unhealthy segment and tenodesis to the healthy tendon has been recommended.¹¹ A 2016 cadaveric study has questioned this recommendation.²⁵ It evaluated allograft versus tenodesis for irreparable peroneus brevis tears and found allograft to be superior in regard to restoration of peroneus brevis tension. Currently there are no clinical studies comparing allograft reconstruction to tenodesis.