Introduction
This chapter provides a review of foot and ankle anatomy and examination followed by an evidence-based discussion of the major provocative tests employed to diagnose ankle and foot injuries. Epidemiologically, foot and ankle complaints are the third most common musculoskeletal reason for adult patients to present in a primary care setting, ranking only behind back and knee pain. In the pediatric population, foot pain is the most common musculoskeletal complaint in patients under 15 years of age. We review anatomy, discuss basic principles of examination related to the foot and ankle, and focus on specific testing for common clinical scenarios. Our goal is to provide the clinician with an understanding of the science (or lack thereof) that guides our examination and its subsequent interpretation.
General Definitions
Before discussing the specifics of examination, it is necessary to have a fundamental understanding of anatomic terminology to effectively communicate the general alignment and movement of the foot. Complex multiplanar joint movements and joint-to-joint interactions generate the motions we simplify in our clinical exam. There is a lack of consistency complicated by the fact that we use terms to describe relationships to both the body and the foot itself. Varus and valgus use the midsagittal plane of the body as a reference point. However, abduction and adduction reference the longitudinal axis of the foot. As opposed to the hand, which uses the third ray, the longitudinal axis of the foot is described as a line from the center of the heel through the second metatarsal shaft. For example, hallux valgus ( Fig. 10.1 ) uses the midsagittal axis of the body, whereas abduction of the hallux is deviation of the great toe away from the foot and actually toward the body. This can be even more confusing when considering terms such as metatarsus adductus ( Fig. 10.2 ), which again, references the position of the metatarsals in relation to the body.
Tibiotalar, talocalcaneal, and transverse tarsal motions are complex, interdependent, and not confined to one plane. For this reason, we will clarify our use of the following terms: dorsiflexion and plantar flexion refer to tibiotalar joint motion, while calcaneus and equinus define the ankle’s static position; inversion and eversion delineate talocalcaneal (subtalar) joint movement; internal rotation and external rotation of the ankle refer to combined tibiotalar and talocalcaneal motion; and pronation and supination are composite movements involving the midfoot and forefoot. Pronation is characterized by external rotation and abduction of the forefoot relative to the tibia combined with hindfoot eversion, thus plantarflexing the medial column. Supination elevates the medial column through internal rotation and adduction of the foot on the tibia combined with hindfoot inversion.
Anatomy and Physical Examination
Inspection
Assessment of the foot and ankle begins with observation of a patient’s gait pattern and static standing posture and the style and wear pattern of the shoes. Shoes, particularly well-worn shoes, can provide evidence about foot position and gait patterns. Wear on the lateral heel is associated with a varus hindfoot, while significant medial wear is typically seen in pes planus.
Particular attention must be given to careful skin inspection of dorsal, plantar, and interdigital regions of all feet, but especially the neuropathic foot (eg, patients with diabetes with peripheral polyneuropathies), to examine for bruising, erythema, pressure sores, nail abnormalities, blisters, and calluses. Be observant of any pigmented melanotic areas because melanoma of the foot accounts for 1.5% to 7% of cutaneous melanomas in a predominantly white population and up to 72% in darker skinned populations. As skin pigment increases, the overall incidence of cutaneous melanoma decreases, but the rate of acral lentiginous melanoma seems to stay the same. These lesions are often not identified or are misdiagnosed as benign lesions at initial presentation, which can result in a delay in diagnosis and treatment and subsequent negative effect on patient outcome.
The weight-bearing posture should be observed with both shoes and socks removed. In general, alignment can be classified as neutral, cavovarus ( Fig. 10.3 ), or planovalgus ( Fig. 10.4 ). Although there are numerous variations, most feet fall into one of these categories. The Johnston County Osteoarthritis Project reported on 1691 adult patients (age = 68.6 ± 9.1 years) who were evaluated for racial differences in foot disorders and alignment type ( Table 10.1 ). Pes cavovarus is defined as a high medial arch and varus heel. It can be associated with numerous complaints, including lateral ankle instability, peroneal tendon pathology, ankle arthritis, and lateral foot overload. Although originally used to describe the appearance of the foot due to post-compartment syndrome muscle contractures, the “peek-a-boo” heel sign (see Fig. 10.3 ) has become a valuable clinical exam tool for the “subtle cavovarus foot.” The peek-a-boo heel sign is viewed from the front with the patients’ feet pointing straight ahead. If the examiner can identify the medial border of the plantar fat pad, there is some component of varus hindfoot alignment. Although the peek-a-boo heel sign is commonly referenced in the literature, to our knowledge, there has not been a study to evaluate the diagnostic accuracy of this test. A cavus foot can be the result of a plantar flexed first ray elevating the arch and tipping the hindfoot into varus, from rigid hindfoot varus, or a combination of the two. The Coleman block test can be used to determine the flexibility of the hindfoot deformity and assess for forefoot driven hindfoot varus. The Coleman block test is performed by placing a block under the lateral column of the foot and unloading the first metatarsal by allowing it to hang over the edge. If the hindfoot is flexible and corrects into valgus, then it is said to be forefoot-driven hindfoot varus. If the hindfoot remains in varus, then the etiology may be secondary to abnormal morphology or pathology of the talus, calcaneus, or subtalar joint.
| Total Sample n = 1691 | African Americans n = 528 (31.2%) | Whites n = 1163 (68.8%) | Unadjusted OR (95% CI) | Adjusted OR (95% CI) * | |
|---|---|---|---|---|---|
| Pes planus | 391 (23.1%) | 202 (38.8%) | 189 (16.3%) | 3.19 (2.53–4.04) | 2.94 (2.31–3.75) |
| Pes cavus | 79 (4.7%) | 8 (1.5%) | 71 (6.1%) | 0.24 (0.11–0.50) | 0.28 (0.13–0.59) |
* Adjusted for age, sex, body mass index, and education; reference = white.
Contrary to the “peek-a-boo heel” sign, the “too-many-toes” sign is a clinical tool for evaluating pes planovalgus. The examiner observes the patient from behind and looks for exposed toes on the lateral aspect of the tibia. The number of toes visualized can be used to quantify the severity of forefoot abduction associated with hindfoot valgus (see Fig. 10.4 ).
Inspection of the patient’s stance and gait is important. Normally, the foot passively pronates during the initial ground contact in the early stance phase. This subtalar eversion unlocks the transverse tarsal joint to allow for force dissipation. The foot should not remain pronated during heel rise and lift off. As the body transfers over the foot, inversion of the subtalar joint stiffens up the transverse tarsal joint in preparation for toe-off. Failure to initiate heel inversion may be associated with tibialis posterior tendon insufficiency. The foot should contact the ground with the heel first, and the heel should begin to rise at 35% of the gait cycle. Early heel rise may occur as a result of tightness of the gastroc–soleus complex or anterior ankle impingement. Late heel rise may be secondary to weakness of the gastro-soleus musculature.
Palpation
Bones and Joints
The ankle mortise consists of two joints: the distal tibiofibular joint (tibiofibular syndesmosis) and the talocrural articulation (ankle mortise). The talocrural joint involves articulation of the talus with both the tibia and fibula. The foot can be divided into sections: hindfoot, midfoot, and forefoot ( Fig. 10.5 ). The hindfoot consists of the talus and calcaneus. The midfoot includes the navicular, cuboid, and cuneiforms. The metatarsals and phalanges make up the forefoot.
Palpation of the ankle should include the medial and lateral gutters, the tibiotalar plafond, the talar dome, and the syndesmosis. Proximally at the ankle, the medial malleolus of the tibia and the lateral malleolus of the fibula are prominent and should always be palpable. Note that the lateral malleolus of the fibula extends farther distally than does the medial tibial malleolus. When an ankle injury is in question, one should palpate the tibial and fibular shafts several centimeters proximal to the malleoli looking for gross deformity or tenderness. Syndesmotic ankle injuries can be associated with fractures of the proximal fibula (Maisonneuve fracture). This follows the general tenet of orthopedic physical examinations that one should always examine the joints above and below an injury.
In 1992, Stiell and others published a set of guidelines to aid in clinical decision making for the use of radiography in acute ankle injuries. These guidelines became known as the “Ottawa ankle rules” ( Fig. 10.6 ). These “rules” suggest that ankle radiographs are indicated if there is pain in the malleolar zone and bony tenderness at area A or B, or the inability to take 4 complete steps both immediately after the injury and in the ER. Foot radiographs are indicated if there is pain in the midfoot zone and bony tenderness at area C or D, or the inability to take 4 complete steps both immediately and in the ER. Numerous studies have looked at the utility of these guidelines. Bachmann and colleagues performed a systematic review and meta-analysis on 27 studies reporting on 15,581 patients. Their data analysis supports the Ottawa ankle rules as a screening tool with approximately 98% sensitivity and median specificity of 31.5%. They concluded that routine use should reduce the number of unnecessary radiographs by 30% to 40%.
In the setting of a rotational ankle injury with distal fibula fracture or syndesmotic disruption, careful examination of the medial soft tissues is critical. If there is clinical concern for a deltoid ligament injury, stress radiographs should be obtained because numerous studies have shown stress-view radiographs to be more sensitive and specific than physical exam alone. Gravity stress views are as sensitive and generally more comfortable for the patient than manual stressing.
Moving distally, the next joints encountered are the talonavicular and talocalcaneal (subtalar) joints. The talonavicular joint can be palpated dorsally between the extensor hallucis longus and tibialis anterior tendons, medial to the tibialis anterior and laterally, just lateral to the extensor digitorum longus tendons. Gentle lateral and medial rocking of the talocalcaneal and transverse tarsal joints by gripping the calcaneus in the opposite hand while pressing in this location will make the talonavicular joint more readily appreciated. Anterior and slightly distal to the lateral malleolus, a depression between the talus and calcaneus, termed the sinus tarsi , is accessible. Tenderness and swelling at the sinus tarsi may be noted after ankle sprains, which may indicate a subtalar injury component. In addition, it is important to palpate the lateral process of the talus because fractures here, also known as a “snowboarder’s fractures,” are commonly misdiagnosed as an “ankle sprain.” Subacute or chronic pain in the setting of pes planus may indicate subfibular impingement. Once thought to be a benign anatomic variant, the accessory anterolateral talar facet has been shown by several authors to be a potential source of pain in both adult and pediatric flat-footed patients.
The calcaneus has several bony prominences, which can be palpated. The anterior process of the calcaneus and the calcaneocuboid joint should be palpated and any tenderness noted. Posteriorly, the Achilles tendon inserts on the calcaneal tuberosity. Pain and swelling in this region may be related to tendinopathy, enthesopathy, superficial tendo-achilles (“pump bump”), or retrocalcaneal bursitis ( Fig. 10.7 ). In pediatric or adolescent patients calcaneal apophysitis (Sever disease) can occur in this region. Medially, the sustentaculum tali is the prominence just distal to the medial malleolus and functions as the insertion site for the calcaneal attachment of the deltoid and spring ligaments as well as the roof of the fibro-osseous tunnel for the flexor hallucis longus (FHL) tendon. Immediately inferior and distal to the lateral malleolus lies the peroneal trochlea, which divides the peroneus brevis (dorsal to the trochlea) and the peroneus longus (plantar to the trochlea).
Other bony landmarks and structures of clinical importance include the navicular tuberosity medially and the styloid process of the fifth metatarsal laterally. The metatarsal shafts are appreciated on the dorsum of the foot while the metatarsal heads are typically more accessible to palpation on the plantar surface.
Soft Tissue Structures
The medial and lateral collateral ligaments of the ankle are composed of the anterior talofibular ligament (ATFL), posterior talofibular ligament (PTFL), and calcaneofibular ligament (CFL) laterally ( Fig. 10.8 ), and the deltoid ligament complex medially ( Fig. 10.9 ). The ATFL, PTFL, and CFL should each be palpated from their origin on the lateral malleolus to their insertion points. Lateral ankle sprains are the most common sports injuries. Among a series of 321 consecutive acute ankle sprains, Broström described a prevalence of complete ligament rupture in 75% of cases. Of these, isolated rupture of the ATFL occurred in about 65% of cases, combined ATFL–CFL tears in about 20%, and isolated tibiofibular (syndesmosis) rupture in about 10%.
The ATFL is actually an extension of the anterior joint capsule and is in the order of 20 mm long, 10 mm wide, and 2 to 5 mm thick. It originates from the anterior border of the lateral malleolus and inserts distally on the body of the talus just anterior to the articular facet. Its fibers are oriented approximately 75 degrees to the floor. The ligament is most taut and positioned essentially in line with the long axis of the tibia in the plantar flexed ankle. It requires the least load to failure of any of the lateral ligaments. Rupture of this ligament is associated with tearing the anterior joint capsule, and bony avulsion of the fibular malleolus is also relatively common.
The CFL is extracapsular, crosses both the tibiotalar and talocalcaneal joints, and measures on average 2 cm long, 5 mm wide, and 3 mm thick. It is most taut with the ankle in neutral or slight dorsiflexion, when its fibers are positioned in line with the long axis of the tibia. The origin of this ligament, which is 2.5 times stronger than the ATFL, is from the distal pole of the fibular malleolus, and the insertion is into a small posterolateral tubercle on the calcaneus. The CFL constitutes the medial wall of the peroneal tendon sheath as the tendons pass under the lateral malleolus. Broström noted intraoperatively that the ruptures of the CFL were associated with tears of the medial wall of this tendon sheath. Rubin and Witten found the CFL to be lax in weight bearing, and this supports the fact that ankle stability during axial loading derives primarily from the tibiotalar and talocalcaneal joint articulations.
The PTFL, similar to the ATFL, is confluent with the ankle joint capsule. It traverses from its origin on the posterior fibular malleolus to a lateral tubercle on the posterior talus. Its fibers are oriented nearly horizontal. The PTFL is the strongest of the lateral ligaments and is taut only at the extremes of dorsiflexion with avulsion of the lateral malleolus occurring before PTFL disruption.
The deltoid ligament courses from the medial malleolus, dividing into four parts: the anterior and posterior tibiotalar ligaments, the tibiocalcaneal ligament, and the tibionavicular ligament. It has both superficial and deep portions and is stronger than any of the lateral ankle ligaments.
The distal tibiofibular syndesmosis is important because it is involved in many moderate to severe ankle sprains, often termed high ankle sprains. There are four ligaments that make up the distal tibiofibular syndesmosis: the anterior tibiofibular, posterior tibiofibular, transverse tibiofibular, and interosseous ligaments. The anterior tibiofibular ligament is palpable at the anterolateral ankle. Although its proximity to the ATFL may limit the specificity of diagnosing a syndesmotic versus lateral ankle sprain, pain with palpation of this structure seems to be the most sensitive screening test ( Table 10.2 ).
| Test | Sensitivity (%) Ryan a et al. | Sensitivity (%) Sman b et al. | Specificity (%) Ryan a et al. | Specificity (%) Sman b et al. |
|---|---|---|---|---|
| Pain with palpation | 83 | 92 | 63 | 29 |
| Squeeze test | 36 | 26 | 89 | 88 |
| External rotation stress test | 68 | 71 | 83 | 63 |
a Ryan et al. used arthroscopy as the gold standard.
b Sman et al. used magnetic resonance imaging as the gold standard.
Spanning the sole of the foot from the calcaneus to the bases of the proximal phalanges is the plantar aponeurosis or plantar fascia, which is often tender at its medial calcaneal origin when inflamed. The plantar fascia is easier to palpate when tensioned through the windlass mechanism by extension of the metatarsophalangeal (MTP) joints.
The Great Toe
First MTP joint pain can be divided into inflammatory, degenerative, and traumatic. Hallux rigidus (degenerative arthritis of the first MTP joint) presents with pain and/or stiffness. Osteophytes can often be palpated along the dorsal aspect of both the metatarsal head and base of the proximal phalanx. Patients may have pain throughout range of motion (ROM) or only at the extremes of flexion and extension. The diagnosis is confirmed with radiographs, and treatment is typically conservative with pressure relief over the dorsal aspect of the joint and using a carbon fiber or steel insert to limit motion through the joint with walking. Pain at the plantar aspect of the first MTP joint may be seen with a plantar plate injury (ie, “turf toe”) or injury to one of the two sesamoid bones that buttress the FHL tendon just proximal to the MTP joint (ie, sesamoiditis, osteonecrosis, fracture). The sesamoids can typically be palpated, and the point of maximal pain should be noted. Varus and valgus stressing is performed to evaluate the collateral ligaments, and drawer testing is performed to evaluate the integrity of the plantar plate. Plain radiographs are the initial imaging modality of choice looking for fracture, sclerosis, or proximal migration of the sesamoids. Please note that 2.7% to 14.3% of the population will have incidental finding of a bipartite sesamoid.
The Lesser Toes
The differential diagnosis of pain around the lesser MTP joints includes synovitis, metatarsal stress fracture, Freiberg’s infraction, degenerative arthritis, inflammatory arthritis, plantar plate injury/capsular degeneration, and interdigital neuroma. Plantar plate injuries can result in pain and progressive deformity of the MTP joints. Drawer testing is performed to assess for MTP joint instability. It involves grasping the metatarsal shaft in one hand and the proximal phalanx in the other. The MTP of the involved toe should be dorsiflexed 25 degrees before applying a dorsally directed force on the proximal phalanx. Increased translation indicates a positive test result. It is helpful when this is compared with other uninvolved toes. Klein and associates reported on the diagnostic statistics of common physical examination techniques compared with intraoperative findings of a plantar plate abnormality as the reference standard. Pain at the second metatarsal head (98%), edema at the second metatarsal head (95.8%), and a positive drawer sign (80.6%) are the most sensitive physical examination tests for a plantar plate injury. The drawer sign is far more specific (99.8%) compared with pain (11.1%) and edema (11.1%). When evaluating the ability for a drawer test to differentiate between high-grade and low-grade plantar plate tears, Klein and others reported the drawer test maintained a high specificity at 91.5%, but the sensitivity dropped to 22%. If there is clinical concern, both magnetic resonance imaging (MRI) and ultrasound are extremely sensitive in identifying plantar plate injuries.
Tendons
At the medial aspect of the ankle, behind the medial malleolus, pass three tendons along with the posterior tibial artery and nerve through the flexor retinaculum. A useful mnemonic for remembering these structures is “Tom, Dick, and very nervous Harry,” which stands for the posterior t ibialis, the flexor d igitorum longus, v essels (posterior tibial artery), posterior tibial n erve, and the flexor h allucis longus. Passing just anterior to the medial malleolus is the anterior tibialis tendon, which is recognized prominently during ankle dorsiflexion. The extensor hallucis longus tendon can also be palpated as it crosses the dorsomedial ankle and foot on its way to insertion at the great toe.
Posterior to the lateral malleolus pass the peroneus longus and brevis, while the peroneus tertius crosses the ankle anterior to the lateral malleolus just lateral to the extensor digitorum longus. Asking the patient to evert the ankle should allow one to distinguish the peroneus tertius from the extensor digitorum longus ( Fig. 10.10 ). The peroneal tendons should be palpated for tenderness and stability. Peroneal tendon instability can cause painful clicking or snapping over the lateral ankle and is best assessed through resisted eversion in a dorsiflexed position.
Vascular Examination
The pulses of the posterior tibial and dorsalis pedis arteries are both palpable in normal individuals. The posterior tibial pulsation can be found just posterior to the medial malleolus as it runs alongside the tendons of the posterior tibialis, flexor digitorum longus (FDL), and FHL contained by the flexor retinaculum. The pulse of the dorsalis pedis is readily appreciated in the interspace between the proximal aspect of the first and second metatarsals. Pulses should be palpated and documented in every clinical encounter. Despite popular opinion, there is no universally accepted standard grading of pulses. Scales range from a 3- to 5-point grading system. Although a 4-point score seems to be most common (0 = no palpable pulse; 1+ is diminished, but detectable pulse; 2+ is normal; 3+ is bounding), we find descriptive terms to be more clinically valuable. If no pulses are palpable, describe the temperature, color, and capillary refill of the feet and toes to provide a clinical picture of the general vascular status. Perform Doppler ultrasound if available.
Biomechanics
Tibiotalar Joint
Ankle plantar flexion and dorsiflexion are sagittal plane motions that occur primarily at the tibiotalar joint. Dorsiflexion involves cephalad tilting of the foot toward the tibial shaft, with a normal range of 20 degrees. Downward pointing of the foot occurs with plantar flexion, with the normal range of 50 degrees. Interestingly, Siegler and associates showed in vitro that up to 20% of dorsiflexion or plantar flexion motion is generated at the subtalar joint. Limitations of joint motion may be due to any combination of osseous, cartilaginous, ligamentous, musculotendinous, or fibrous restrictions. Ligamentous laxity is common and may contribute to individual differences in the ankle ROM of healthy subjects. In a cohort of 18 healthy subjects who underwent a biomechanical analysis of ankle ROM, Siegler and colleagues found no significant side-to-side differences.
Dorsiflexion is the position of stability for the tibiotalar joint. Rubin and Witten noted that, in a dorsiflexed ankle, the broader anterior part of the talus is in firm contact with the malleoli and resists talar tilt. In dorsiflexion, the fibular malleolus is displaced 2 to 3 mm laterally. The main function of the lateral ankle ligaments is to stabilize the joint near its neutral position, while at extremes of ROM bone-to-bone contact provides stability. Furthermore, several researchers have demonstrated that the ankle articulation is inherently stable under loaded conditions. Boardman and Liu added that the integrity of the anterolateral joint capsule also contributes significantly to ankle stability.
Range of motion of the ankle should be performed with the knee both flexed and extended utilizing the Silfverskiöld test. The foot is dorsiflexed with the knee flexed and then repeated with the knee extended to document the maximum dorsiflexion in both positions. Because the gastrocnemius muscle originates on the posterior femur, the muscle–tendon unit is placed on maximum stretch by extending the knee. By testing with the knee flexed, the proximal gastrocnemius muscle is relaxed. A normal ankle has dorsiflexion of at least 10 degrees with the knee extended and should improve another 10 degrees with knee flexion. Normal dorsiflexion with the knee flexed, which significantly decreases with knee extension, indicates primary gastrocnemius contracture, whereas a contracture that does not improve with knee flexion can represent a capsular contracture, combined gastroc-soleus contracture, or bony impingement.
Talocalcaneal Joint
Hindfoot inversion and eversion occur primarily at the subtalar or talocalcaneal articulation. While some advocate that subtalar motion should be measured with the tibiotalar joint held in neutral dorsiflexion to ensure that the talus is firmly grasped in the mortise, others have noted good joint congruence throughout the range of talocalcaneal motion. Inman noted a large variability in subtalar motion, from 20 to 60 degrees, due to variation in subtalar axis and anatomy, kinematic coupling with the ankle joint, and maintenance of true subtalar neutral positioning. Siegler and coworkers showed that, at extremes of motion, the tibiotalar joint can also contribute to inversion and eversion.
Talocalcaneal motion is assessed with the patient sitting, holding the calcaneus in one hand and the forefoot in the other. The examiner subsequently can move the subtalar joint into inversion and eversion. There is usually twice as much inversion as eversion and a lack of subtalar motion may indicate abnormalities such as arthritis, peroneal spastic flat foot, or tarsal coalition. Excessive inversion may be noted after injury to the lateral ankle ligaments.
Transverse Tarsal Joint (Chopart Joint)
The talonavicular and calcaneocuboid articulations together comprise the transverse tarsal joint. Forefoot supination and pronation occur at this collective joint and should be tested with the hindfoot maintained in subtalar neutral because motion at the transverse tarsal joint is affected by talocalcaneal inversion and eversion. As with the talocalcaneal joint, side-to-side comparison is helpful in determining unilateral restrictions. Decreased transverse tarsal motion may be seen in chronic tibialis posterior tendon insufficiency and arthrosis involving the transverse tarsal joint. Midfoot amputation at this level is commonly called a Chopart amputation.
Tarsometatarsal Joint (Lisfranc Joint)
The cuboid and three cuneiforms adjoin the five metatarsal bones to form the collective tarsometatarsal joint, or Lisfranc joint. Tenderness at the interval between the first and second metatarsal bases may indicate rupture of the Lisfranc ligament and should trigger advanced imaging such as stress-view x-rays or MRI to evaluate for ligamentous injury. Ross and Cronin reported the “plantar ecchymosis sign” as a clinical finding to aid in the diagnosis of Lisfranc injuries.
Extrinsic Muscles of the Ankle and Foot
Plantar Flexion
The triceps surae or gastrocnemius–soleus complex contains the prime plantar flexors of the ankle ( Fig. 10.11 ). The gastrocnemius has medial and lateral heads originating from the medial and lateral femoral condyles, respectively. Their obliquely oriented fibers adjoin into a common Achilles tendon that is also shared by the soleus muscle and inserts into the calcaneal tuberosity. The posterior tibialis, peroneus longus, FDL, and FHL, and to a lesser extent, the plantaris muscle, comprise the accessory plantar flexors of the ankle and foot.
Dorsiflexion
The most important ankle dorsiflexors of the ankle and foot are the tibialis anterior and the extensor digitorum longus. The peroneus tertius and extensor hallucis longus serve as supplemental dorsiflexors.
Inversion and Supination
The main invertors are the tibialis anterior and tibialis posterior muscles, which also contribute to forefoot supination. The FDL and FHL can serve as auxiliary forefoot supinators as well. In a neutral hindfoot, the triceps surae produce calcaneal inversion. However, in a valgus hindfoot, the moment arm of the Achilles actually moves lateral to the axis of the subtalar joint and functions as an evertor.
Eversion and Pronation
The peroneus longus, peroneus brevis, and peroneus tertius act in concert to evert the forefoot. The lateral portion of the extensor digitorum longus can aid in this function.
Intrinsic Muscles of the Foot
Interphalangeal and Metatarsophalangeal Flexion
The FDL and flexor digitorum brevis (FDB), the FHL, and the quadratus plantae all serve as interphalangeal joint flexors. The MTP joints are flexed by the FDL, FDB, FHL, flexor hallucis brevis and flexor digiti minimi brevis, abductor hallucis and abductor digiti minimi, and all the lumbricals and interossei.
Metatarsophalangeal Extension
The extensor digitorum longus and brevis, and the extensor hallucis longus and brevis all contribute to MTP extension.
Neurologic Examination
The tibial nerve enters the ankle and foot region coursing behind the medial malleolus and subsequently dividing into medial and lateral plantar branches. The tibial nerve supplies the ankle plantar flexors, invertors, and extrinsic toe flexors in the leg and then divides into the medial and lateral plantar branches that are analogous to the median and ulnar nerves in the hand. The medial plantar nerve innervates the abductor hallucis, FDB, flexor hallucis brevis, and first two lumbricals and provides cutaneous sensation to the medial three and a half digits. The lateral plantar nerve supplies the quadratus plantae, flexor digiti quinti brevis, abductor digiti quinti, the lateral three lumbricals, the interossei, and cutaneous sensation to the lateral plantar aspect of the foot. The first branch of the lateral plantar nerve (Baxter’s nerve) can become entrapped between the fascia of the abductor hallucis and the medial aspect of the quadratus plantae or the calcaneus itself. The point of maximal tenderness is typically more dorsal than that associated with plantar fasciitis, and pressure in this area can cause radiation of pain into the lateral foot.
While the peripheral nerves innervating the structures of the ankle and foot are not typically palpable, the examiner should be aware of interdigital neuromas (eg, Morton’s neuroma) ( Fig. 10.12 ) and nerve entrapments, including tarsal tunnel syndrome (entrapment of the tibial nerve as it crosses the ankle through the flexor retinaculum), as sources of foot pain ( Fig. 10.13 ).
