Introduction

Acute posterior tibialis tendon injury in the athlete is rare^1,2 but must be considered in the differential diagnosis of a patient who presents primarily with tenderness, swelling, and pain over the medial ankle or plantar medial midfoot. Antecedent to the acute presentation, there often is a history of less severe prodromal symptoms more consistent with a chronic interstitial rupture with tendinosis. The chronic picture is seen more often in the middle-aged to elderly patient, athlete or not, that was especially popularized by the late Kenneth A. Johnson, MD,^3–5 with whom I had the honor of fellowship training. Others,^1,2,6–9 of course, also have contributed to a further understanding of the diagnosis and treatment of this condition.

Although most of the literature emphasizes chronic posterior tibialis tendon disease, the ultimate presentation of the acutely injured athlete may be very similar to the chronic form. Therefore given the rarity of acute injury versus the more commonly seen chronic presentation, posterior tibialis tendon “dysfunction,” rather than “injury,” probably is a more accurate description and title for this chapter.

Anatomy and Biomechanics

The posterior tibialis muscle is a resident of the deep posterior compartment of the leg, originating along the proximal one third of the tibia and intraosseous membrane. Distally, its tendon travels posterior, then inferior, through the medial malleolar groove, changing direction abruptly almost 90 degrees. The stout retinaculum of the long flexors prevents the tendon from subluxating over the medial malleolus.¹⁰ Because the posterior tibialis tendon is without a mesotenon, there is an area of relative hypovascularity from this acute turn at the medial malleolus to the medial navicular insertion. These factors of hypovascularity and the mechanical stress of an acute turn of the tendon as part of a strong, weight-bearing leg muscle (second only to the gastrocnemius) make the tendon predisposed to injury in this area.

Because the posterior tibial tendon travels posterior to the axis of the ankle and medial to the axis of the subtalar joint, it serves as an ankle plantarflexor and foot invertor via the transverse tarsal joint (talonavicular and calcaneocuboid joints).¹¹ The tendon also has multiple slip attachments to the capsule of the naviculocuneiform joint, all three of the cuneiforms, the cuboid, and their respective metatarsal bases in the plantar arch.^4,12 The posterior tibialis tendon therefore is primarily a midfoot invertor and dynamically supports and elevates the medial longitudinal arch. It also indirectly supports the hindfoot because of its medial malleolar pulley action and intimate relationship to the deep deltoid ligament, plantar medial talonavicular joint capsule, and spring ligament (calcaneonavicular ligament).¹³ With relatively little elongation because of rupture, the tendon becomes incompetent to support the medial longitudinal arch initially, resulting in the acquired adult flatfoot with forefoot pronation and abduction (Fig. 8-1). However, over time other ligamentous structures are affected, including the talonavicular joint capsule, deltoid ligament, and spring ligament. The stretching out or even frank rupture of these structures eventually leads to a valgus inclination of the hindfoot and external rotation of the calcaneus, also resulting in contracture of the Achilles tendon as it becomes a hindfoot everter¹¹ (Fig. 8-2). Clinically, this may result in impinging pain and swelling in the subfibular or sinus tarsi area as the calcaneus abuts against the lateral malleolus. In very severe or neglected cases, a valgus tilt of the ankle may be seen as the deltoid ligament becomes incompetent.

Figure 8-1 Dorsal-plantar view demonstrating the normal foot (A) and the posterior tibialis tendon incompetent foot (B). With external rotation or abduction of the forefoot, the medial talar head becomes more uncovered by the navicular as it rotates externally. The calcaneus also secondarily rotates externally and tilts into more valgus.

Figure 8-2 Posterior-anterior view of the normal (A) and posterior tibialis tendon incompetent ankle and hindfoot (B). With external calcaneal rotation, the talar head translates plantarward. This also leads to increased valgus tilting of the calcaneus and subfibular or sinus tarsi impingement.

Diagnosis

Usually, a detailed history, conscientious physical examination, and x-rays will establish the diagnosis of a posterior tibialis tendon injury.

History and questions to be answered

Sometimes the history alone will provide the examiner with enough information to suggest the diagnosis.

• What was the mechanism of injury? Specifically, did the foot sustain an eversion twisting injury, especially on impact from tripping or a fall? Or, was there a sudden increase in the level of athletic activity temporally related to the onset of symptoms?

• Were there prodromal symptoms of possible tendon degeneration before the acute injury?

• Has the athlete noticed that the arch on the involved side is “flatter,” the foot is “turned out,” the ankle “turned in,” or complained that the injured foot is “weaker”?

• When unshod on a hard, wet floor surface, such as at bath time, does the patient notice a different footprint or a “sucking sound” because of a vacuum effect of the collapsed arch on the symptomatic side?

• Has the athlete noticed more medial shoe sole wear or “running over” the medial vamp?

• Is there any history of gout, pseudogout, or autoimmune disease?

• Are there sensory (dysesthesias or paresthesias) complaints?

• In terms of predisposing risk factors, is there a history of oral steroid use, injected steroids in the area of the tendon, diabetes, smoking, vasculopathy, obesity, or worsening of a preexisting pes planus deformity?

Physical examination and questions to be answered

For comparison, both unclothed and unshod lower extremities from the midthigh distally to the toes should be carefully examined.

• Is there a valgus knee deformity (genu valgum) of the symptomatic side? (This may precipitate or exacerbate posterior tibialis tendon dysfunction, especially if chronic.)

• Is there tenderness and swelling along especially the terminal course of the tendon, generally between the medial malleolus and the navicular insertion or, less commonly, in the posterior aspect of the medial malleolus (Fig. 8-3, A and B)?

• Is there tenderness in the insertional area of the anterior tibialis tendon?

• In viewing the weight-bearing patient from behind, is there increased forefoot abduction or pronation (the so-called “too many toes sign”) (Fig. 8-4)?

• Does the patient have difficulty heel rising with all of his or her weight on the injured side (“single foot heel rise” test), or if he or she is able to heel rise, does the hindfoot fail to invert or invert less than the normal side (Fig. 8-5)?

• Is there tenderness and swelling laterally in the sinus tarsi or subfibular area, suggesting impingement, especially in the patient with deformity (Fig. 8-6)?

• Is the Achilles tendon contracted?

• Are there abnormal sensory findings that might suggest peripheral neuropathy, especially in the diabetic patient?

• Is there a positive Tinel’s sign over the tibial nerve in the medial ankle or plantar foot sensory deficits that might suggest a tarsal tunnel syndrome?

• Is there a tender and swollen bony prominence in the area of the medial navicular, suggesting an accessory navicular or stress fracture?

• Is the medial malleolus itself tender, thus suggesting a stress fracture?

• Are there any dysvascular findings (absent posterior tibial or dorsalis pedis pulses, delayed capillary refill, cyanosis, toe hair loss, and dystrophic nail changes)?

Figure 8-3 Usual area of maximal tenderness and swelling along the terminal course of the posterior tibialis tendon between the medial malleolus and medial navicular insertion. Occasionally, this can extend to the area posterior to the medial malleolus.

Figure 8-4 The positive “too many toes” sign in the posterior tibialis dysfunctional right foot is appreciated when examining the weight-bearing patient from behind. The forefoot is abducted/pronated and the hindfoot is in greater valgus, resulting in more toes seen laterally in the right foot when compared with the left.

Figure 8-5 Notice hindfoot inversion in the normal left foot. Although patients with posterior tibialis tendondysfunction may be able to perform the single-foot heel-rise test, notice that the hindfoot does not invert, orinverts less, than the normal foot. This may be due to some residual function of the posterior tibialis muscletendon unit with assistive recruitment of the long toe flexors.

Figure 8-6 Zone of tenderness and swelling indicative of impingement in the subfibular or sinus tarsi area, often seen with more severe posterior tibialis tendon dysfunction with hindfoot valgus deformity.

X-rays and questions to be answered

Ideally, weight-bearing x-rays of the symptomatic foot and ankle should be taken. Also, comparison views of the other foot and ankle often are helpful diagnostically.

Ankle x-rays

• Do films demonstrate a medial or valgus tilt (Fig. 8-7, A)?

• Are there arthritic changes with joint space narrowing, osteophytes, or loose bodies medially?

• Is there any evidence of a medial malleolar stress fracture or medial talar dome osteochondritis dissecans (Fig. 8-7, C)?

• Is there major arterial (anterior and posterior tibial) calcification?

Figure 8-7 Radiographs of patients with medial ankle or midfoot pain and swelling demonstrating medial talar tilt because of primary deltoid ligament incompetency (A) accessory navicular (B) medial talar dome osteochondritis dissecans with a coronal magnetic resonance imaging (MRI) view (C) and medial column arthiritis. (D) all of which can mimic to varying degrees the clinical presentation of posterior tibialis tendon dysfunction.

Foot x-rays

• Is there an accessory navicular or possible avulsion fracture of the medial navicular (see Fig. 8-7, B)?

• Do the films of the foot reveal arthritic changes of the medial subtalar (additional Broden’s views may be helpful), talonavicular, naviculocuneiform, or medial tarsometatarsal joints (Fig. 8-7, D)?

• Is there any evidence of a tarsal coalition, especially in the periadolescent athlete?

• On the lateral view, is the talo-first metatarsal angle negative, especially if it is more so than a comparison view of the contralateral foot (Fig. 8-8)?

• On the anteroposterior (AP) view, is there an increased talo-first metatarsal angle or increased “uncovering” of medial talar head at the talonavicular joint, thus indicating forefoot abduction, again especially when compared with the contralateral foot (Fig. 8-9)?

• As in the ankle, is there arterial calcification of the dorsalis pedis or posterior tibialis arteries?

Figure 8-8 Lateral weight-bearing views demonstrating the midfoot sag of the posterior tibialis incompetent right foot. I prefer this more simplistic measurement of the angle between the long axis of the talus (a) and the I metatarsal (b). The resultant angle (c) is greater in the involved foot. In this case in the normal left foot, these lines are virtually parallel. Also, notice that the subtalar joint is less clearly seen in the symptomatic right foot because of superimposition of the talus and calcaneus from a hindfoot valgus deformity.

Figure 8-9 Anteroposterior (AP) weight-bearing views demonstrating abduction deformity resulting from posterior tibialis tendon incompetency in the right foot. Again, I prefer this more simplistic measurement of the ankle between the long axis of the talus (a) and the I metatarsal (b). The resultant angle (c) is great in the involved right foot. Also, notice that the medial talar head is more uncovered by the navicular in the involved foot (d).

Magnetic resonance imaging (MRI)

Although rarely necessary, if the history, physical examination, and x-rays fail to conclusively determine the diagnosis of a posterior tibialis tendon injury, or to confirm the diagnostician’s impression, then an MRI may be indicated.^14,15 An MRI also is helpful to determine the extent of acute injury or chronic tendinosis and thus guide treatment, especially if surgery is planned, and may predict the postoperative clinical outcome.¹⁵ Finally, the MRI may help to determine other conditions that may mimic, be concomitant with, or even contribute to posterior tibialis tendon disease^{8,10,13,16,17} (Table 8-1). Perhaps of historical interest, others have proposed the diagnostic use of tenography⁷ or ultrasound,¹⁸ but their sensitivity is significantly less than that of a high-quality MRI.

Table 8-1 Differential diagnosis

Medial ankle arthritis	Medial subtalar joint or medial column arthritis
Medial ankle instability with deltoid ligament rupture/laxity	Symptomatic accessory navicular with synchondrosis disruption
Medial malleolar or talar stress fracture	Medial navicular bony avulsion or stress fracture
Medial talar dome osteochondritis dissecans	Acute injury or tendinosis of the flexor hallucis longus or flexor digitorum longus tendons
Tarsal tunnel syndrome	Peri-insertional anterior tibialis tendon rupture or tendinosis
Tarsal coalition, especially in periadolescent athletes	Medial ankle or hindfoot/midfoot crystalline or autoimmune arthritis

Generally, the MRI will reveal fibrous tendinotic longitudinal hypertrophy or bulbous enlargement of the tendon, sometimes with cystic or longitudinal voids (Fig. 8-10, A). Also, there usually is increased tenosynovial fluid within the sheath surrounding the tendon^18,19 (Fig. 8-10, B). These findings usually are seen between the medial malleolus and navicular but also can extend proximally into the posterior medial malleolar area.

Figure 8-10 Magnetic resonance imaging (MRI) findings of posterior tibialis tendon dysfunction. (A) Sagittal view at the level of the medial malleolus (MM) demonstrating longitudinal void within the tendon. (B) Transverse view at the level of the talus (T) also demonstrating intratendinous voids and increased fluid around the tendon.

Disease Staging

Once the diagnosis is firmly established, the stage of posterior tibialis tendon disease, as popularized by Kenneth A. Johnson’s seminal work, is important to determine the proper course of treatment. Johnson initially described stages I to III,⁵ but a stage IV^11,20 has more recently been described that involves a valgus inclination of the talus with degenerative arthritis of the ankle joint (Table 8-2). This is exceedingly rare in the active athlete and will not be elaborated upon beyond its mention.

Table 8-2 Disease stages

Stage I is essentially peritendinitis and/or tendon degeneration (tendinosis) with a normal tendon length and no deformity. Stage II is characterized by an incompetent or lengthened tendon with a mild flexible deformity. Stage III encompasses the findings of the preceding stages, but with a greater degree of deformity that also may be rigid. X-rays of the stage III foot may further reveal significant arthritic changes in any or all of the triple joint complex (subtalar, talonavicular, and/or calcaneocuboid joints) or naviculo-cuneiform joints, as well as clinical signs and symptoms of subfibular or sinus tarsi impingement.