MusculoSkeletal Exam

A B

Figure 12.77 (A) Modified Helfet test: the knee is flexed 90 degrees and the midlines of the patella and tibial tuberosity are in alignment. (B) In extension, the tibial tuberosity is lateral to the patellar midline (normal).

Figure 12.78 The apprehension test for patellar subluxation and dislocation.

Wave of fluid

Figure 12.79 The wipe test for swelling in the knee. Attempt to move the fluid from medial to lateral first. Then attempt to wipe the fluid from lateral to medial over the patella. If a bulge of fluid is noted inferior and medial to the patella, the test result is positive for a small joint effusion.

Tests for Joint Effusion

Wipe Test

This test is sensitive to detecting small amounts of joint fluid. The patient lies in the supine position with the knee extended if possible. Fluid is first massaged across the suprapatellar pouch from medial to lateral. Next, try to move the fluid from lateral to medial, using a wiping action over the patella. If you see a bulge of fluid inferomedially to the patella, a joint effusion is present (Figure 12.79).

Ballotable Patella

If a large effusion is suspected, you can test for it by having the patient lie in the supine position with the knee extended as much as possible. Push down on the patella. The fluid will flow to either side and then return underneath the patella, causing the patella to rebound upward (Figure 12.80).

Functional Anatomy

The Ankle

The ankle is a synovial articulation composed of three bones: the tibia, the fibula, and the talus. Although intimately interrelated with the foot, the ankle and foot have separate and distinct functions. The ankle is the simpler of the two structures. It is an extraordinarily stable linkage between the body and its base of support, the foot. Generally, the ankle lies lateral to the body’s center of gravity. Therefore, the ankle joint is subjected to varus as well as compressive loading (Figure 13.1). The structure of the ankle is that of a bony mortise. It is bounded medially by the malleolar process at the distal end of the tibia, superiorly by the flat surface of the distal end of the tibia (the tibial plafond), and laterally by the malleolar process of the distal end of the fibula. The smaller fibular malleolus extends distally and posteriorly relative to the medial malleolus. As a result, the transmalleolar axis is externally rotated approximately 15 degrees to the coronal axis of the leg (Figure 13.2). Anteriorly, the mortise is deepened by the anterior tibiofibular ligament. Posteriorly, it is buttressed by the bony distal projection of the tibia (posterior malleolus) and the posterior tibiofibular ligament. Within this mortise is set the body of the talus. The talus articulates with the tibial plafond by its large superior convexity (the dome). It also presents an articular surface to each of the malleoli. The dome of the talus is wider anteriorly than it is posteriorly. As such, the talus becomes firmly wedged within the ankle mortise on dorsiflexion. This creates medial–lateral tension across the distal tibiofibular syndesmosis and ligament. The intact ankle mortise primarily allows the talus a single plane of motion (flexion–extension),

Compression

Varus

Figure 13.1 The ankle is lateral to the center of gravity and therefore is subject to a varus stress as well as compression.

Posterior

15˚

Anterior

Figure 13.2 The transmalleolar axis is externally rotated 15 degrees.

with only a modest amount of anterior–posterior glide. Therefore, this increased stability of the ankle during dorsiflexion affords the means to isolate and assess medial–lateral ankle ligament integrity and subtalar inversion–eversion mobility.

The ankle is solely responsible for transmission of all weight-bearing forces between the body and the foot. The ankle is remarkably immune to the otherwise universally observed degenerative changes of senescence, seen in other large synovial articulations. This unusual and unique sparing of the ankle joint is probably a consequence of a combination of factors, including the ankle’s requirement of limited degrees of freedom and its extreme degree of stability. However, to accommodate the severe stresses of daily activities and changes in ground contours, the ankle is complemented by a complex of accessory articulations that comprise the foot. The most significant of these is the subtalar (talocalcaneal) articulation.

The Foot

The primary functions of the foot are to provide a stable platform of support to attenuate impact loading of the extremity during locomotion, and to assist in the efficient forward propulsion of the body. To accomplish these tasks, the foot is made up of three sections. These sectionsathe hindfoot, the midfoot, and the forefoota are in turn composed of multiple mobile and semirigid articulations that afford foot conformity to varying surface topographies. The bony elements of the foot are arranged to form a longitudinal and a transverse arch. These arches are spanned across the plantar aspect by soft-tissue tension bands that act as shock absorbers during impact (Figure 13.3A).

The foot has 26 bones distributed among the hindfoot, midfoot, and forefoot (Figure 13.3B). The hindfoot represents one-third of the total length of the foot. It contains the two largest bones of the foot, the calcaneus and the talus. The larger is the calcaneus (heel bone).

The calcaneus lies beneath and supports the body of the second bone, the talus. The talus (ankle bone) is the only bony link between the leg and the foot. The tibia articulates with the talus in the middle of the hindfoot.

The midfoot contains the small, angular navicular, cuneiforms (medial, middle, and lateral), and cuboid bone. The midfoot makes up slightly more than onesixth of the overall length of the foot. Little movement occurs within the midfoot articulations.

The forefoot represents the remaining one-half of the overall length of the foot. It is composed of miniature long bones, five metatarsals and 14 phalanges.

Chapter 13 The Ankle and Foot

Structural integrity of the foot is dependent on the combination of articular geometry and soft-tissue support. All articulations of the foot are synovial. The soft-tissue support is provided by static (ligamentous) and dynamic (musculotendinous) stabilizers. The failure of either articular or soft-tissue structural integrity will result in ankle dysfunction, foot dysfunction, reduced efficiency, arthritis, and bony failure (fatigue fractures).

The support of the talus is afforded posteriorly by the anterior calcaneal facet and distally by the navicular bone. There is a void of bony support at the plantar aspect between the calcaneus and navicular, beneath the talar head. Support of the talar head across this void is totally dependent on soft tissues that span this gap (Figure 13.4A). Statically, this support is provided by the fibrocartilaginous plantar calcaneonavicular (spring) ligament. Dynamically, the talocalcaneonavicular articulation is supported by the tibialis posterior tendon and its broad plantar insertion onto the plantar medial aspect of the midfoot. Because the head of the talus is only supported by soft tissue, in the presence of soft-tissue or ligamentous laxity and muscular weakness, the head of the talus can sag in a plantar direction. This will force the calcaneus and foot laterally, with medial rotation of the foot about its long axis. This rotation of the foot beneath the talus has been termed pronation. The primary locus of pronation is therefore at the subtalar joint. Rotation of the subtalar joint causes causes the talus to twist within the ankle mortise. There is little possibility for movement of the talus within the ankle mortise due to the rigid anatomy of that joint. Therefore, this torsional load is transmitted through the talus to the leg and lower extremity, with a resultant internal rotational torque on the leg and a supination torque on the midfoot (talonavicular, calcaneocuboid, and naviculocuneiform articulations) (Figure 13.4B).

Pronation serves two critical functions. First, it dampens impact loading of the medial arch of the foot during locomotion, which would otherwise exceed the tolerance of the medial arch. Second, pronation of the talus creates a relative internal rotational torque of the leg, external rotation–valgus of the calcaneus, and abduction–supination of the midfoot. This configuration passively stretches the triceps surae at its attachment to the supramedial aspect of the calcaneus. It also stretches the tibialis posterior, flexor digitorum longus, and flexor hallucis longus and toe flexors as it begins to lift the heel from the foot in midstance. This passive stretching of these muscles serves to increase their mechanical efficiency.

The Ankle and Foot Chapter 13

The forefoot is composed of five digits. Each digit has a long bone (metatarsal) and two or more phalanges. These articulations of the forefoot are basically hinge joints. Their stability is primarily due to medial and lateral ligaments. Volarly, the interphalangeal joints are stabilized against excessive dorsiflexion by firm volar ligaments called plates.

The digits of the foot can be divided into three columns (Figure 13.4C). The medial digit is the largest. It is more than twice the dimension of any of the other digits. This reflects its greater importance in weightbearing and push-off activity. The second ray, together with the first, forms the medial column of the forefoot. The third ray represents the “stable” or minimally mobile central column of the foot. The lateral two rays are progressively more capable of movement. They combine to form the lateral column of the forefoot, the fifth metatarsal being the most mobile of all the digits. Because of the insertion of the peroneus brevis tendon onto the base of the fifth metatarsal, it is the site of excessive traction load when the foot is supinated during an injury such as a typical ankle sprain. The resultant excessive traction of the peroneal tendon on the base of the fifth metatarsal leads to the commonly seen fifth metatarsal fracture and more complex Jones fracture of the metatarsal shaft.

Observation

The examination should begin in the waiting room before the patient is aware of the examiner’s observation. Information regarding the degree of the patient’s disability, level of functioning, posture, and gait can be observed. The clinician should pay careful attention to the patient’s facial expressions with regard to the degree of discomfort the patient is experiencing. The information gathered in this short period can be very useful in creating a total picture of the patient’s condition.

Note whether the patient is allowing the foot to rest in a weight-bearing position. Assess the patient’s willingness and capability to use the foot. How does the patient get from sitting to standing? Is the patient able to ambulate? Observe the heel-strike and push-off phases of the gait pattern. Note any gait deviations and whether the patient is using or requires the use of an assistive device. Details of any gait deviations are described in Chapter 14.

The patient can be observed in both the weightbearing and non-weight-bearing positions. Observe

the patient’s shoes. Notice the wear pattern. Ask the patient to remove his or her shoes and observe the bony and soft-tissue contour and the bony alignment of the foot. Common bony deformities that you might see include pes cavus, pes planus, Morton’s foot, splaying of the forefoot, mallet toe, hammer toes, claw toes, hallux valgus, hallux rigidus, tibial torsion, and bony bumps (i.e., pump bump). Soft-tissue problems include calluses, corns, plantar warts, scars, sinuses, and edema. You should also observe the patient’s toenails. Look for muscular atrophy, especially in the gastrocnemius. Observe for signs of vascular insufficiency including shiny skin, decreased hair growth, decreased temperature, and thickening of the toenails. Pay attention to the integrity of the medial arch during weight-bearing compared to non-weight-bearing. Check the alignment of the calcaneus and notice if there is increased inversion or eversion during weight-bearing.

Subjective Examination

The ankle and foot are subjected to large forces during the stance phase of the gait cycle. Although the foot is very agile and adapts well to changing terrain, it is vulnerable to many injuries. In addition, the foot often presents with static deformities because of the constant weight-bearing stresses placed on it. The foot can also be involved in systemic diseases such as diabetes and rheumatoid arthritis. Does the patient present with a previous history of any systemic diseases?

You want to determine the patient’s functional limitations. Has he or she noticed a gradual change in the shape or structure of the foot? Has the patient noticed generalized or localized swelling? Did the swelling come on suddenly or over a long period of time? Has the patient been participating regularly in a vigorous activity like running? What are the patient’s usual activities? What is the patient’s occupation? Are abnormal stresses placed on the feet because of his or her job? Is the patient able to stand on toes or heels without difficulty? Is the patient stiff when he or she arises in the morning or after sitting? Is the patient able to ascend and descend steps? Can he or she adapt to ambulating on various terrains? Does one particular terrain offer too much of a challenge?

Does any portion of the foot feel numb or have altered sensation? Parasthesias in the ankle and foot may be secondary to radiculopathy from L4, L5, S1,