Peroneal Tendon Complex: Injury and Rehabilitation
By Stephen M. Pribut, DPM
Introduction
While ankle sprains are the most common musculoskeletal athletic injury,(1) the peroneal tendon complex (PTC) is often injured concurrently. Injury to the PTC 
has become widely recognized as an acute injury and a significant source of lingering pain and disability. These injuries are frequently correlated with inversion ankle sprains and chronic ankle instability (CAI).
Anatomy
The peroneal tendon complex (PTC) includes the peroneus longus and brevis tendons, the os peroneum, and their restraining components (Figure 1). We will discuss the anatomy, clinical significance and conservative treatment of injury to the PTC.
Peroneal Muscles and Tendons
The peroneus longus and brevis muscles are located within the lateral compartment of the leg. The vascular supply is primarily from the posterior peroneal artery. Innervation of the peroneals is from the superficial peroneal nerve. The well positioned constraints which serve to maintain proper anatomical position of the PTC include the superior peroneal retinaculum, the retromalleolar groove, the shared tendon sheath, the individual tendon sheaths, the peroneal tubercle, the inferior peroneal retinaculum, and the peroneal groove below the cuboid (Table 1).
Peroneus Longus
The origin of the peroneus longus muscle is from the head and upper two-thirds of the lateral surface of the fibular body and from the intermuscular septa adjacent to the muscles of the anterior and posterior leg. The musculotendinous junction occurs proximal to the lateral malleolus. The peroneus longus along with the peroneus brevis enters the fibular fibro-osseous tunnel behind the fibular malleolus and shares a common synovial sheath. The peroneus longus tendon changes direction three times in the foot: at the lateral malleolus, the peroneal tubercle, and at the cuboid notch. A hypertrophied tubercle may be a cause of injury of the PLT.(2)
An ossified os peroneum is found in approximately 20% of individuals at the cuboid notch (Figure 2).(3). The tendon runs below the cuboid and crosses obliquely to insert into the base of the first and second metatarsal and the lateral facet of the medial cuneiform bone.
Peroneus Brevis
The peroneus brevis muscle originates at the distal two thirds of the lateral
aspect of the body of the fibular and the adjacent intermuscular septa. It passesbehind the fibula where it lies adjacent to the fibula and deep to the peroneus longus while passing through the fibro-osseous tunnel. The insertion is at the tuberosity of the base of the fifth metatarsal bone. An os vesalianum is found near the insertion in less than 1% of people.(4)
Variants
The peroneus tertius muscle is found in approximately 90% of people and begins at the distal third of the anterior fibula. The muscle is usually confluent with the extensor digitorum muscle and ends before the inferior extensor retinaculum. The peroneus quartus is an anomalous muscle found in 6.6% to 22% of individuals. It begins at the peroneus brevis and inserts into the peroneal tubercle after travelling through the shared peroneal tendon sheath. (5)
Biomechanics and Injury
Peroneal tendon injures are a direct result of their anatomy and biomechanics. (5) The peroneal muscles are multi-joint muscles. Early in stance, the PTC is subject to passive stretch as the gastrosoleus acts proximally as a tibial decelerator. Late in stance phase, the PTC acts as a weak plantar flexor at the ankle joint.
At the subtalar joint (STJ), the peroneals act as pronators and are antagonists to the tibialis anterior and tibialis posterior muscles. Additionally, the peroneus longus muscle (PLM) plantarflexes the first ray and is a pronator at the midtarsal joint. The peroneals are most active in mid- and terminal stance, functioning to stabilize the foot. (6,7) Recent studies have demonstrated weakness of functional evertor strength in CAI. (8)
The PTC is subject to strain forces when the foot is inverted or supinated about the STJ. A sudden inversion force or chronic
overuse may injure the PTC or the lateral ankle. The most frequent injuries to the PTC are traumatic tendinopathy, a tear, or a subluxation of the peroneal tendons. (9) Tendon subluxation is believed to occur with the foot in a dorsiflexed position and the peroneal tendons contracting strongly. (10)
Risk factors associated with peroneal tendon injuries may be seen in Table 2. (11, 12) Multi-directional sports, such as soccer, tennis, and basketball, are associated with these injuries. While peroneus brevis injuries are frequently suspected at the level of the lateral malleolus, injury to the distal peroneus longus is often undetected. Additional associated injuries include injury to the cuboid, the os peroneum, or fifth metatarsal. (3, 13) Differential diagnoses are listed in Table 3.
Peroneal tendon complex injury is considered a risk factor and contributor to CAI. (14, 9) A recent study showed that a brief bout of pain posterior to the lateral 
malleolus preceding an inversion ankle injury was associated with MRI evidence of peroneal tendinosis in 95% of cases. (13) Up to 75% of those suffering inversion ankle injuries may have a recurrence of injury or are subject to ongoing symptoms related to chronic ankle instability (CAI). (15, 16) Examination at the time of surgery for recalcitrant CAI often demonstrates injury. A retrospective review of 136 patients who underwent a Broström-Gould ankle reconstruction found that 53.3% required operative intervention for peroneal tendon pathology. (14)
Examination of sixty-four consecutive acute ankle inversion injuries by MRI revealed that 30% of the subjects suffered an associated tendon injury. (17) These injuries, when unrecognized, may contribute to ongoing symptoms. Estimates range from 30% to 70% of inversion ankle injuries may recur or have lasting symptoms. These ongoing symptoms diminish sensorimotor functioning and lead to decreased physical activity and concomitantly a diminished quality of life (18). It has been reported that 32% of ankle inversion injuries are still symptomatic seven years after the injury. (19)
Painful Os Peroneum Syndrome (POPS)
The os peroneum (OP) is a sesamoid bone found within the peroneus longus tendon (PLT) of most people. It is usually located just proximal to the cuboid tunnel. The OP is frequently fibrocartilaginous, often bipartite, and is only visible on x-ray 6–20% of the time (Figure 3).
The OP is subject to both fracture and contusion. Bone callus formation during healing can lead to tendinopathy of the peroneus longus tendon and it may also play a role in tears of the tendon. When the OP is injured, the MRI may show fluid around the PLT and bone marrow edema of the cuboid. (20)
Physical Examination
A history and physical examination will reveal the cause of many injuries. While the inversion movement which causes the injury occurs rapidly, the full effects may not be obvious for several hours. The lag between injury and effect will lead many patients to forget the inversion event. The history may reveal previous ankle sprain, fracture, or other lateral foot injury. Peroneal subluxation may be associated with a sensation of painful clicking.
A methodical physical examination follows the principles of look, touch, and move. Examine for swelling, color, general alignment, structure, and symmetry. Thoroughly palpate the lateral foot and ankle and explore the peroneal tendons through their entire course. Peroneus brevis tears often occur behind the fibula, while peroneus longus injury may occur at the cuboid groove or more distally. Note the strength of the peroneal tendons and pain during resisted ankle eversion. Also note pain in response to dorsiflexion of the first ray or an inability to resist the dorsiflexion. (5) Be sure to check the ankle for ligamentous disruption.
Peroneal subluxation may be tested by flexing the knee and asking the patient to actively dorsiflex the ankle with resisted eversion. The test is positive if the peroneal tendons are seen to subluxate anterior to the fibular malleolus. Intra-sheath subluxation is suspected if their position translates relative to each other. (5) The peroneal compression test suggests peroneus brevis tendinopathy. To perform this test, evert and dorsiflex the foot while compressing the fibular groove.(20)
Diagnostic Imaging
The Ottawa protocol outlined in Table 4 should only be used for acute ankle injuries and not for late injury evaluation. On x-ray, carefully evaluate all the 
lateral boney structures. Figure 4 shows a hairline Jones fracture that went undetected the previous night at an urgent care center (Figure 4). A visible fleck of bone at the fibula indicates possible subluxation of the peroneal tendons from the fibular groove. A Harris view assists in assessing the peroneal tubercle and the retromalleolar groove. (21, 22) Be on guard for a fracture of the os peroneum or distraction of multipartite fragments (Figure 5). Fractures of the os peroneum may best be assessed using a CT scan which better reveals the border of the ossicle.
Ultrasound can be useful to detect peritendinous fluid, or partial or complete rupture, but it requires an experienced examiner.
Magnetic resonance imaging (MRI) shows the anatomy in best detail. Fluid surrounding the tendons are best seen on T2-weighted or short tau inversion recovery (STIR) images. These images are useful to assess subtle injury to the cuboid and base of the fifth metatarsal. The MRI finds more pathology than is clinically relevant in some cases while it may miss other pathology. (23) MRI has a positive predictive value of less than 50%. (24, 25)
Outline of Treatment
High level evidence-based medicine is the goal we seek to attain. However, there are times when the evidence is weak, contrary, wrong, or lacking. There is only scant material written on rehabilitation for PTC injury. Researching the rehabilitation of ankle injuries is a reasonable place to begin crafting a program for the PTC. (26) Most recent overviews have come to realize the flaw of not using 
adequate protection during the earliest stage of therapy. (16, 27)
The most consistently recommended therapy for rehabilitation of an acute ankle sprain, CAI, and for prevention to reduce the risk of future re-injury is balance training. (27, 28, 29, 30)
Proposed Functional Rehabilitation of PTC Injury
Phase I: Protection, rest, ice, compression, and elevation.
Initial therapy requires protection of the injured area. A removable pneumatic cast boot serves as both protection and compression and may be removed for exercise and evaluation. (21) An ankle brace alone is not effective since the stabilization achieved is inadequate. The tendons must be protected from forces that place them under stretch, including dorsiflexion moments applied to the foot. It is helpful to protect the mid-foot, mid-tarsal joint, and first ray from forces which translate into strain forces on the peroneal tendons. The removable cast boot is used for one to four weeks depending upon the severity of the injury.
Ice may be applied for 20 minutes on/40 minutes off for three to six times per day for the first 48 hours. Ibuprofen or another NSAID may be helpful.
Phase II: Motion
Do not rush the patient into vigorous muscle and strength exercises. This has been part of chronically failing regimens previously used for the ankle. Gentle range of motion exercises may be performed.
Phase III: Neuromotor
Proprioception, balance, and muscle strength are keys to successful recovery. The most efficacious tool to accomplish these goals is the 20” wobble board. This appears to reach optimal angular relationships at maximum excursion to train the neuro-facilitative responses needed in gait.
Other proprioception and balance exercises may also be used. The most popular are Romberg one leg balance exercises and the simplified STAR excursion exercises. (31, 32)
Muscular strength exercises may be augmented using exercise band therapy. Recent evidence has shown more proximal muscle training may also assist in recovery.
Limitation of dorsiflexion and equinus may be addressed by posterior muscle group stretching and active exercises such as the heel roll-up. Toe crunches strengthening the intrinsic muscles are also helpful to stabilize the mid-tarsal joint and decrease PTC forces needed for this stabilization.
Gentle foam rolling of the calf muscles may help mobilize the ankle.
Phase IV: Return to Activity
The balance and proprioceptive exercises from Phase III should all be continued for at least three months. Specific training for a return to activity may begin.
Preparation for return to full activity includes beginning with walking, progressing to running, cutting, and sideways movements needed for sport. It generally requires four to six weeks to return to most sports but occasionally twelve weeks may be needed.
Orthotics
Evidence has pointed to orthotics as being helpful in treating CAI. Orthotics are 
also helpful in treating PTC injuries. Orthotic modifications to reduce the strain on the peroneal tendons and lateral foot structures are important components of treatment. Research also indicates that orthotics produce proprioceptive and balance improvements. (33)
Feet that suffer these injuries often have a lateral shift of the STJ location, which increases the supinatory moment of ground reaction forces. The orthotic modifications I use are designed to alter these moments and allow the peroneals to function optimally. These modifications include a 0/0 rearfoot post with “no lateral bevel” (Figure 6). This makes the orthotic less prone to cause excessive supination. You may use a low level of cast inversion and medial skive depending upon the foot type. In 
addition, you may use about 3 degrees of lateral forefoot valgus wedging to the sulcus, especially for patients who do not contact with the rear foot. Additional modifications seen in Table 6 are based on Richard Blake’s suggestions for excessive supination. (34)
Summary
We have briefly reviewed the anatomy, injuries, and rehabilitation for injuries to the PTC (Table 7). There is much to research and write about this topic. Don’t stop learning. Your patients benefit from your knowledge.
Outline of Therapeutic Treatment for Peroneal Tendon Injuries
Acute Care:
PRICE: Protection, Rest, Ice, Compression, Elevation
Pneumatic walking boot
NSAIDs
Intermediate:
ROM exercises
Wean from cast boot
Long Term:
Proprioception exercises
Wobble Board Training
STAR with imbalance platform
Custom Orthotic:
No rear foot post bevel
Full length
Minimal Cast correction
Possible FF Valgus Posting
Additional corrections as needed
More images coming:
Figure 1. Know your anatomy. Tablet-based apps help demonstrate the anatomy to your patients. (Image courtesy 3d4Medical Ltd. “Essential Anatomy 5”)
Figure 2. Normal os peroneum.
Figure 4. Hairline Jones fracture. Tender to touch and visible on x-ray.
Figure 5. Fragmented os peroneum. Healing bone callus visible.
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Bio: Dr. Pribut is a Clinical Assistant Professor of Surgery at George Washington University Medical School. He serves on the Runner’s World Board of Advisors. He is a past president of the American Academy of Podiatric Sports Medicine. Dr. Pribut is in private practice in Washington, DC.