LEG, ANKLE, AND FOOT INJURIES
The leg, the portion of the lower extremity between the knee and the ankle, is vital for locomotion. The ankle is the linking joint between the foot and the leg and is crucial to performance of all running and jumping sports. The foot is the terminal appendage of the lower extremity and functions as the contact point between the body and the terrain.
Athletic competition places a great deal of stress on the leg, ankle, and foot. As an athletic trainer understanding of the anatomy of this region and possible injuries, as well as patient care during rehabilitation, can make a great difference in the success of recovery. In this section, we will cover the anatomy of the leg, ankle, and foot, as well as possible injuries and rehabilitation techniques.
I. Leg Anatomy
Osseous (Bony) structures
The tibia is slightly concave at both the knee and the ankle to accommodate the articulations with the femur and the talus, respectively. At the ankle, it widens and extends medially to become the medial malleolus, which provides bony stability to the ankle joint. Because the tibia is protected only by skin along its anterior and medial borders, it is readily accessible to palpation and examination throughout its length. This exposure also makes it vulnerable to frequent injury by direct impact blows such as contusions and fractures.
The fibula is a long, slender bone lying posterior and lateral to the tibia and connected to the tibia in three ways: by a true joint at is proximal end (knee); by the interosseous membrane (a thick, sheet-like ligament) along its length; and by strong ligaments at its distal end (ankle). It can also be palpated with relative ease proximally at the fibular head and neck, and then again along its distal third where it ends as the lateral malleolus. In thin individuals, the common peroneal nerve can be "rolled" over the neck of the proximal fibula with the examiner's finger approximately 3 cm from the tip of the fibular head (at the knee). The nerve is very close to the skin surface at this location and vulnerable to compression by straps, wraps, and direct blows. Such compression would be manifested early by a decrease in sensation on the dorsum (top) of the foot and then by progressive motor loss of ankle dorsiflexion, toe dorsiflexion, and foot eversion with more severe or long-lasting injury.
The leg is divided by distinct fascial connection into four compartments: the anterior, lateral, superficial posterior, and deep posterior. The anterior compartment, which is most commonly involved in exertional compartment syndromes, contains the tibialis anterior muscle and the extensor muscles to the great and small toe (the extensor hallucis longus and the extensor digitorum longus). The deep peroneal nerve runs together with the anterior tibial artery deep within the anterior compartment. It provides the motor supply to the anterior compartment muscles and the sensory supply to the first web space in the foot.
The lateral compartment contains only two muscles, the peroneus longus and peroneus brevis, which plantar flex and evert the ankle. The superficial peroneal nerve is the only major neurologic structure in the lateral compartment. It innervates these two muscles and provides sensation to most of the dorsal foot.
The superficial posterior compartment contains two muscles: the gastrocnemius and the soleus. The muscles of the deep posterior compartment include the tibialis posterior (which plantar flexes and inverts the hindfoot); the flexor digitorum longus (long flexor of the toes); and the flexor hallucis longus (long flexor of the great toe). The tibial nerve, posterior tibial artery, and peroneal artery are also contained in the deep posterior compartment and supply its structures.
II. Normal Function and Gait
To understand lower extremity athletic injuries, it is important to recognize the biomechanics of normal gait, which requires knowledge of the body planes of motion. Single plane movements include dorsiflexion and plantarflexion (sagittal plane), inversion and eversion (frontal plane), and abduction and adduction (horizontal plane). Motion or deformity involving more than one plane is described as triplane.
During gait, forces are absorbed and dissipated as the body adapts to the walking surface. Most leg injuries are strains, tears, or overuse syndromes from cumulative impact loading. In normal running, the lateral aspect of the foot strikes the ground with the tibia externally rotated. As the stance phase progresses, body weight is carried over the foot. With pronation, the foot contact forcesare dissipated. As the stance phase continues, the foot reaches midstance. Halfway through midstance, the nonweight-bearing leg swings forward and the pelvis rotates, externally rotating the weightbearing leg. Foot supination through the subtalar joint creates a rigid foot in preparation for the toe off.
Excessive foot prontion is associated with medial tibial stress syndrome and tibial and fibular stress fractures. One possible explanation is that the medial soleus muscle causes calcaneal inversion with concentric contraction and then undergoes eccentric contraction as the foot is pronated, which can alter an athlete's normal running mechanics.
III. Physical Examination
An examination of the leg is relatively straightforward and should include an evaluation of the joints above and below the site of injury or symptoms. The tender areas must be visually inspected, palpated, and compared with the normal opposite leg. As a athletic trainer, you should check for subtle anatomic abnormalitites such as limb-length discrepancy; excessive femoral anteversion (increased internal rotation of the hip and little external rotation); hamstring tightness (limited straight leg raise); genu varum (bowlegs) or genu valgum (knock-knees); foot over-pronation; and excessive Q-angle. The entire extremity should be evaluated for a complete understanding of the causative factors in an athlete's lower leg complaint.
How to detemine leg alignment to the heel and heel alignment to the forefoot deserves special mention. To determine leg alignment to the heel, the athletic trainer should sit behind the standing athlete with the athlete's heel positioned directly under the tibia in a symmetrical fashion. The athletic trainer should imagine two vertical lines, one bisecting the posterior heel. The intersection of these two lines determines the valgus angle.
Measuring the alignment of the forefoot to heel to determine forefoot varus or valgus is done with the athlete in both standing ad sitting positions. Ideal forefoot position demonstrates a neutral alignment with respect to the perpendicular axes of the heel. An examiner positioned behind the athlete will be able to see a positive "too many toes" sign for unilateral flatfoot deformity. When the longitudinal arch is collapsed and viewed from behind, more toes on the affected side can be seen than on the opposite side. This sign usually indicates a posterior tibial tendon dysfunction or a spring ligament injury that causes compensatory motion through the subtalar (talocalcaneal) joint or transverse tarsal joint (talonavicular and calcaneocuboid joints). However, these findings are rare in the young athlete, whose overly pronated foot position is more commonly a bilateral dynamic deformity that occurs during the stance phase of walking and running. Symptoms secondary to overly pronated feet can often be alleviated with the use of an orthosis that has a semirigid arch support and slight medial heel posting.