CHAPTER 12 The foot
The foot is the athlete’s main contact area with the ground—an obvious point, but one which helps account for the very high number of conditions affecting this area in sport. An athlete’s foot may have to withstand forces two or three times greater than bodyweight, and this may be repeated more than 5000 times every hour when running. Most sports involve some sort of running or jumping, and so the foot is continually called upon to provide both stability and shock attenuation.
The first metatarsal bone joins proximally to the first cuneiform to form the first ray complex. Distally, the bone forms the first metatarsophalangeal (MP) joint with the proximal phalanx of the hallux. The first MP joint is reinforced over its plantar aspect by an area of fibrocartilage known as the volar plate (plantar accessory ligament). This is formed from the deep transverse metatarsal ligament, and the tendons of flexor hallucis brevis, adductor hallucis, and abductor hallucis. It has within it two sesamoid bones which serve as weight-bearing points for the metatarsal head (Fig. 12.1).
Movement of the joint is carried out by flexor hallucis longus, flexor hallucis brevis, extensor hallucis longus, the medial tendon of extensor digitorum brevis, and abductor and adductor hallucis. This fairly complex structure is often taken for granted but does give rise to a number of important conditions.
Turf toe is a sprain involving the plantar aspect of the capsule of the first MP joint. It is most often seen in athletes who play regularly on synthetic surfaces, and results from forced hyperextension (dorsiflexion) of the first MP joint. Normally this joint has a range of 50–60°, but with trauma the range may be forced to over 100°. The condition is quite common, with studies of American football players showing that 45% of athletes had suffered from turf toe at some stage (Rodeo et al., 1989a).
Forced hyperextension of the first MP joint causes capsular tearing, collateral ligament damage and damage to the plantar accessory ligament. Sometimes force is so great that disruption of the medial sesamoid occurs (Fig. 12.2). Examination reveals a hyperaemic swollen joint with tenderness over the plantar surface of the metatarsal head. Local bruising may develop within 24 hours. Differential diagnosis must be made from sesamoid stress fracture (insidious onset) and metatarsal or phalangeal fractures (site of pain and radiograph).
Treatment aims at reducing pain and inflammation and supporting the joint by taping (Fig. 12.3). An oval piece of felt or foam with a hole in the middle is placed beneath the toe, the hole corresponding to the metatarsal head. The first MP joint is held in neutral position and anchors are applied around the first phalanx and mid-foot. Strips of 2.5 cm inelastic tape are applied as stirrups between the anchors on the dorsal and plantar aspects of the toe. In each case the tape starts at the toe and is pulled towards the mid-foot, covering the first MP joint. The mid-foot and phalanx strips are finished with fixing strips.
A number of factors may predispose the athlete to turf toe. The condition is more common with artificial playing surfaces than with grass (Bowers and Martin, 1976). Artificial turf is less shock-absorbing, and so transmits more force directly to the first MP joint. Sports shoes also have an important part to play. Lighter shoes tend to be used with artificial playing surfaces. These shoes are more flexible around the distal forefoot, and allow the MP joint to hyperextend. In addition, shoes which are fitted by length size alone, rather than width, may cause problems for athletes with wider feet. This person must buy shoes which are too long to accommodate his or her foot width. Such a shoe increases the leverage forces acting on the toe joints and allows the foot to slide forwards in the shoe, increasing the speed of movement at the joint.
Preventive measures include wearing shoes with more rigid soles to avoid hyperextension of the injured joint. In addition, semi-rigid (spring steel or heat-sensitive plastic) insoles may be used. Some authors recommend the use of rigid insoles as a preventive measure when playing on all-weather surfaces, for all athletes with less than 60° dorsiflexion at the first MP joint (Clanton, Butler and Eggert, 1986).
An increased range of ankle dorsiflexion has been suggested as a risk factor which may predispose an athlete to turf toe (Rodeo et al., 1989b). However, in walking subjects, when the ankle is strapped to reduce dorsiflexion, the heel actually lifts up earlier in the gait cycle, causing the range of motion at the metatarsal heads to increase (Carmines, Nunley and McElhaney, 1988). This increased range may once again predispose the athlete to turf toe (George, 1989), so the amount of dorsiflexion per se may not be that important. If injury has recently changed the range, the athlete may not have had time to fully adapt to the altered movement pattern, and the altered foot/ankle mechanics in total may be the problem.
As with many soft tissue injuries, if incorrectly managed the condition may predispose the athlete to arthritic changes in later life. In the case of turf toe, this may occur as calcification of the soft tissues around the injury site, presenting as hallux valgus or hallux rigidus.
Hallux valgus (hallux abductovalgus or HAV) usually occurs when the first MP joint is hypermobile, and the first ray is shorter than the second (Morton foot structure). When this is the case, the second metatarsal head takes more pressure than in a non-Morton foot (Rodgers and Cavanagh, 1989) (Fig. 12.4). In addition, hallux valgus is more common in athletes who hyperpronate. Often the combination of hyperpronation and poorly supporting fashion footwear exacerbates the condition.
From Rodgers, M.M. and Cavanagh, P.R. (1989) Pressure distribution in Morton’s foot structure. Medicine and Science in Sports and Exercise, 21, 23–28. With permission.
Pronation of the subtaloid joint reduces the stabilizing effect of the peroneus longus muscle, allowing the 1st metatarsal to displace more easily. The increased motion leads to the combined deformity of abduction and external rotation of the first toe (phalanges) and adduction and internal rotation of the first metatarsal. Joint displacement occurs at both the MP joint and the metatarsal/medial cuneiform joint (Lorimer et al., 2002).
As the first MP joint dorsiflexes during the propulsive phase of running, the instability allows the hallux to deviate from its normal plane. Adduction and axial rotation occur, and the long flexors which normally stabilize the joint now themselves become deforming influences, causing bowstring effect. As the first metatarsal head adducts, the sesamoids sublux and eventually erode the plantar aspect of the first metatarsal head—this is one source of pain. Compensatory stress is placed on the joints proximal and distal to the first MP and further pain arises through synovial inflammation and capsular distraction. Eventually, secondary osteoarthritis occurs in the first MP joint and sesamoids. High heeled and constrictive footwear may predispose to the condition.
Hallux valgus may occur in one of two types. Congrous hallux valgus is an exaggeration of the normal angulation between the metatarsal and the phalanx of the 1st toe. Importantly the joint surfaces remain in opposition and the condition does not progress. The normal angulation of the 1st MPJ (measured between the long axis of the metatarsal and that of the proximal phalanx) is 8–20°; in congruous hallux valgus this angle may increase to 20–30° (Fig. 12.5A). Once the angle increases above 30°, the joint surfaces move out of congruity and may eventually sublux. This condition is now classified as pathological hallux valgus, and may progress, with the angulation increasing to as much as 60° (Magee, 2002).
After Magee (2002) with permission.
Bunion formation to the side of the first metatarsal head is common. The bursa over the medial aspect of the MPJ thickens and a callus develops. In time an exostosis is seen on the metatarsal head and the three structures combined lead to the cosmetic change which is noticeable (Fig. 12.5B). A gel padded bunion shield can help reduce both abnormal shearing and compressive stress to ease symptoms when walking. At night a bunion regulator which resists the abduction forces acting on the 1st toe can help to protect the overstretched soft tissues and reduce inflammation and pain.
Management of this condition is initially to stabilize the first MP joint by correcting faulty foot mechanics (especially hyperpronation) and advising on correct athletic footwear. If conservative management fails, surgery may be required. If the deformity is purely soft tissue in nature, the bunion may be removed, and the dynamic structures around the first toe realigned. If bony deformity is present, osteotomy (bone realignment), arthroplasty (forming a new joint) or arthordesis (joint fusion) may be necessary.
A reduction in movement of the first MP joint, hallus limitus, may progress to complete immobility or hallux rigidus where the joint is ankylosed. The condition is more common when the first metatarsal is longer than the second. Pain is generally worse during sporting activities, and occurs especially when pushing off. On examination, the joint end feel is usually firm, and limitation of movement is noted to dorsiflexion. To differentiate between a tight flexor hallucis longus and joint structures, the foot is assessed both with the foot dorsiflexed and everted (tendon on stretch) and then plantarflexed and inverted (tendon relaxed).
In hallux limitus, movement may be restricted by either a tight flexor hallucis longus (FHL) or joint structures. To differentiate between the two, movement range is assessed both with the tendon on stretch (FHL limits) and with the tendon relaxed (joint limits).
Limitation of motion through muscle tightness responds well to stretching procedures, while joint limitation which is soft tissue in nature is treated by joint mobilization. Distal distraction and gliding mobilizations with the metatarsal head stabilized are particularly useful (Cibulka, 1990). Where bony deformity is present, surgery is indicated. A number of surgical procedures are available for hallux conditions, and the interested reader is referred to Horn and Subotnick (1989) for an excellent review.
A Taylor’s bunion is seen over the base of the 5th metatarsal. It is more common in athletes who have a cavus foot with splaying toes, and may cause abrasion in unyielding sports footwear such as ski boots, cycling shoes and rollerboots. Management is generally conservative, encouraging athletes to select sports shoes with a wide toe box. Severe cases may require surgical intervention.
The plantar fascia (plantar aponeurosis) is the thickest fascia in the body. It attaches from a point just behind the medial tubercle of calcaneus and runs anteriorly as five slips. As the slips approach the metatarsal heads, they split into superficial and deep layers (Fig. 12.6A). The superficial layer attaches to superficial fascia beneath the skin, while the deep layer divides into medial and lateral portions to allow the passage of the flexor tendons. Each of the five portions attaches to the base of a proximal phalanx and to the deep transverse ligament.
As the toes dorsiflex and the 1st MP joint is extended prior to toe off, the fascia is wound around the metatarsal head (windlass effect). In so doing the fascia is tightened, shortening the foot and elevating the longitudinal arch (Fig. 12.6B). The combination of these effects supinates the foot and provides a rigid lever for push off. As the foot contacts the ground at heel strike the arch lowers and the foot pronates, becoming a mobile adaptive unit. The plantar fascia is stretched as the foot lengthens.
As we have seen in Chapters 10 and 11 tendon inflammation (patella tendonitis and Achilles tendonitis) is now thought to be an incorrect term based on the pathology of the tissue affected. Similarly the term plantar fasciitis implies tissue inflammation but histological findings do not support this concept. Reviewing 50 post surgical cases Lemont, Ammirati and Usen (2003) found degeneration and fragmentation of the plantar fascia together with bone marrow vascular ectasia (expansion). No inflammatory markers were present, implying that the condition is a fasciosis rather than a fasciitis. This fact is important when treating the condition, as steroid injections (anti-inflammatory) often used to treat plantar pain have a strong association with plantar ruptures (Murphy, 2006). In a study of 765 patients with plantar fascial pain Acevedo and Beskin (1998) found 51 patients who had received corticosteriod injection. Of this subgroup 44 ruptured, with 68% showing sudden onset tearing and 32% gradual onset tearing. At follow-up 26 subjects still showed symptoms 1 year after rupture.
Pain in the plantar fascia is common in sports which involve repeated jumping, and with hill running. Overuse may cause microtears and degeneration at the fascial insertion, and nodules from the fascial granuloma can occasionally be felt (Tanner and Harvey, 1988).
Normally, during mid-stance the foot is flattened, stretching the plantar fascia and enabling it to store elastic energy to be released at toe off. However, a variety of malalignment faults may increase stress on the fascia. Excessive rearfoot pronation will lower the arch and overstretch the fascia, and a reduction in mobility of the first metatarsal may also contribute to the condition (Creighton and Olson, 1987). In addition, weak peronei, often the result of incomplete rehabilitation following ankle sprains, will reduce the support on the arch, thus stressing the plantar fascia. Congenital problems such as pes cavus will also leave an athlete more susceptible to plantar fasciitis. The condition is exacerbated if the Achilles tendon is tight, or if high-heeled shoes are worn. Pain is often worse when taking the first few steps in the morning until the Achilles tendon is stretched.
Sports shoes play an important part in the course of this condition. Inadequate rearfoot control may fail to eliminate hyperpronation, and a poorly fitting heel counter will allow the calcaneal fat pad to spread at heel strike, transmitting extra impact force to the calcaneus and plantar fascia. On a hard surface, the shock-absorbing qualities of the shoe are important, and a patient’s footwear should always be examined.
Pain is usually over the calcaneal attachment of the fascia or its medial edge. Pain may be localized to the heel as though the athlete is ‘stepping on a stone’, or may present as a burning pain over the arch. The problem must be differentiated from rheumatoid conditions which often give bilateral pain, and Sever’s disease which gives pain to the insertion of the Achilles tendon. In addition fat pad pain (see below) will give heel pain over the whole pad rather than a single point as with plantar fasciitis.
Taping the foot (Fig. 12.7) may often give surprisingly rapid relief. The foot is locked in neutral position and an anchor strap placed just behind the metatarsal heads. Three strips of tape (medial, lateral and central) are then passed from the anchor over the heel to stop on the posterior aspect of the calcaneum. A horseshoe-shaped fixing strip secures the tape behind the heel. Additional strips may be placed transversely across the foot from the metatarsal heads to the calcaneal tubercle.
Trigger point therapy for the plantar muscles (especially quadratus plantae and flexor hallucis) may give excellent results even long term. The thickness of the tissues in this area means that a massage tool should be used to save the therapist’s fingers. The athlete sits with the therapist sitting towards the end of the treatment couch. Ischaemic pressure is placed onto the muscles and fascia in the sole of the foot and the tissues are gradually tightened as pain allows by plantarflexion of the foot and flexing the toes (windlass effect). Specific soft tissue mobilization may be performed by pressing the fascia into the pain producing direction and repeating this action at a lower (painless) grade and holding the fascia stretch for 4−5 seconds. The athlete can be taught self-management by pressing the sole of the foot down onto a hard ball (marble or snooker ball) or crossing the legs and pressing directly into the sole with the thumbs.
Extensibility of the 1st MP joint is assessed both weight bearing (foot on the floor) and non-weight bearing (patient on the couch), with normal values of 65° quoted (Murphy, 2006). Movement limitation should be categorized as bony requiring joint mobilization or soft tissue requiring stretching. The plantar fascia is stretched by using a combination of 1st MP extension and ankle dorsiflexion (Fig. 12.8).
More permanent management may require rearfoot posting to control excessive pronation. In addition, strengthening the intrinsic foot musculature is important. Although the plantar fascia is inert, stress on the structure may be increased when the intrinsic foot musculature is weak. The role of foot strengthening, including actively increasing the arch height, and ‘gripping’ the floor with the toes, may have a re-education effect on plantar proprioception.
The calcaneus is covered by elastic adipose tissue in the same way as the finger tips. The fat cells are arranged in columns made from fibrous septa which lie vertically. As weight is taken, the walls of the columns bulge and spring back as the weight is released. With age the septa lose elasticity and the thickness of the heel pad reduces.
Athletes who wear poorly padded sports shoes and those who land heavily on the heel when jumping may bruise this area. In more severe cases rupture of the fibrous septa may occur causing spillage of the enclosed fat cells (Reid, 1992). In turn, the loss of the heel pad shock-absorbing mechanism places excessive compression stress onto the calcaneum.
Pain is increased when walking barefoot. Typically, athletes complain of pain first thing in the morning when getting out of bed. The first few steps are exquisitely tender, later subsiding to a dull ache. Pain is brought on by prolonged standing and walking.
Management is by additional padding, and preventing the heel pad from spreading. Non-bottoming shock-absorbing materials are useful, and taping to surround the heel and prevent spread of the pad is effective in the short term (Fig. 12.9). Activity modification is required during the acute stage of the condition.
Morton’s neuroma (plantar neuroma) affects the plantar interdigital nerve between the third and fourth metatarsal heads. The condition is not a true neuroma (nerve tumour), but simply a localized swelling and scarring of the nerve. Symptoms may occur spontaneously and are often described as feeling like ‘electric shocks’ along the sensory nerve distribution. The condition is more common with runners (particularly when sprinting and running uphill) and dancers, and is often aggravated by wearing narrow, high-heeled shoes. The sustained dorsiflexed position of these activities stretches the digital nerve causing inflammation. Once swollen, the nerve is open to entrapment between the metatarsal heads, and eventually the nerve is scarred and permanently enlarged to form a neuroma.
The patient’s pain may be reproduced by direct pressure over the neuroma while compressing the forefoot medially and laterally to shorten the transverse arch (Mulder’s sign). The condition must be differentiated from Freiberg’s disease (see below) which occurs in the younger athlete.
Mulder’s sign is a test for Morton’s neuroma. The test is positive if pain is reproduced by palpating the neuroma while compressing the forefoot in a medial−lateral direction to shorten the transverse arch.
If the condition is caught in its oedematous stage, alteration of footwear (larger toe box and lower heel), ice application and ultrasound are effective. Injection with corticosteroid and local anaesthetic is also used. Padding the area with orthopaedic felt (Fig. 12.10) to take some of the bodyweight off the neuroma can give temporary relief. The arms of the pad rest on the adjacent metatarsals, leaving the area of the neuroma free.
Once the neuroma has formed, surgical excision under local anaesthesia may be required, with some studies showing improvement in 80% of patients (Mann and Reynolds, 1983). There may be a permanent loss of sensation over the plantar aspect of the foot supplied by the digital nerve, but in some cases regeneration can occur between 8 and 12 months after surgery. Follow-up after 2 years (mean 29 months) has shown an 88% reduction in pain with overall satisfaction being excellent or good in 93% of sporting patients (Akermark, Saartok T and Zuber, 2008).
Freiberg’s disease (lesion) is an osteochondrosis of the 2nd metatarsal head, most commonly seen in young ballet dancers. Pain occurs over the bony head of the metatarsal (contrast this with Morton’s neuroma which gives pain between the metatarsals) and is aggravated by raise onto the ball of the foot. In longer standing cases x-ray reveals flattening of the metatarsal head with damage to the epiphyseal plate. Initially no changes may be apparent on radiographs (Fig. 12.11), with bone scan or MRI being more sensitive. Management is by modification of weight bearing activities and padding over the metatarsal head to offload the joint and reduce direct pressure over the painful area. Orthotic prescription is often required.