Introduction to Rehabilitation of the Foot and Ankle

Justin K. Greisberg, MD

Jenna Baynes, MD

Dr. Greisberg or an immediate family member serves as a paid consultant to Extremity Medical; has received research or institutional support from Extremity Medical; has received nonincome support (such as equipment or services), commercially derived honoraria, or other non-research–related funding (such as paid travel) from Saunders/Mosby-Elsevier; and serves as a board member, owner, officer, or committee member of the American Orthopaedic Foot and Ankle Society. Neither Dr. Baynes nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article.

Introduction

The human foot is one of the few anatomic structures that separates us from other primates. While one could argue that other parts of the limbs, such as the hand or shoulder, are just modifications of the basic primate design, the foot has evolved from a position of mobility to one of stability. The basic primate foot is adapted for grasping, while the human foot is meant for prolonged weight bearing.

In simplest terms, the foot provides a stable foundation, with a “universal joint” (ankle/hindfoot) that can keep the leg vertical while the foot accommodates any uneven terrain. The rigid arch provides a lever arm to amplify contractions of the Achilles tendon.

Foot and Ankle Anatomy

Bone Morphology

The talus is the center of the ankle/hindfoot complex. A large part of the bone is covered with articular cartilage, and there are no tendon insertions on the bone. With little soft-tissue coverage, the blood supply to the talus is tenuous, and injuries can result in avascular necrosis and collapse.

The anterior process of the calcaneus is just below the talus, but the body of the calcaneus sits a bit more laterally, to give some valgus to the hindfoot. The Achilles tendon inserts on the large tuberosity, which is also the sole hindfoot point of contact with the ground.

The navicular, cuboid, and cuneiforms pack in together tightly (Figure 52.1). The first metatarsal is much larger in diameter than the other metatarsals. While it is quite mobile in other primates, in the human, the first metatarsal is tucked in tightly alongside the second in a position of stability. In the ideal human foot, the first metatarsal should take about 40% of normal weight-bearing forces.

Joints

The distal tibia and fibula come together to form the ankle mortise, a highly constrained socket for the talus. The talus rotates in the mortise to provide the majority of plantarflexion and dorsiflexion motion.

The talus also articulates with the navicular (talonavicular joint) and the calcaneus (subtalar joint). Although these joints are generally separate, the two joints form the hindfoot complex. Together, they provide most of the inversion and eversion. These joints actually make a three-dimensional screw motion, so that inversion is accompanied by some plantarflexion and forward translation of the foot, and eversion is accompanied by dorsiflexion and some posterior translation. Fusion of either joint eliminates most of the motion in the other.

Although there are three joints around the talus, in reality, the ankle and hindfoot joints act together as a universal joint, to allow the foot to accommodate any terrain while the leg remains vertical.

The calcaneocuboid provides a small amount of additional hindfoot motion. Together with the talonavicular joint, these
two joints, also called the Chopart joints, can provide a moderate amount of plantar/dorsiflexion when the ankle is stiff or fused.

Figure 52.1 Illustration of fhe hindfoot, which contains the subtalar and talonavicular joints, where most inversion/eversion occurs. The midfoot provides very little motion, and actually is more important for rigidity than flexibility. (Modified from Oatis CA: Kinesiology—The Mechanics and Pathomechanics of Human Movement. Baltimore, Lippincott Williams & Wilkins, 2004.)

The articulations between the navicular, the cuneiforms, and the medial three metatarsals are relatively rigid. These joints have evolved in the human for stability, not mobility. Insufficient stability of these midfoot joints can result in foot deformities, such as a collapsed arch or hallux valgus.

Motion at the metatarsophalangeal (MTP) joints is helpful during the gait cycle, especially extension/dorsiflexion during heel rise, but stiffness/fusion of the first MTP joint is surprisingly well tolerated (as long as there is no pain). The interphalangeal joints are not essential to normal human locomotion.

Muscles

The Achilles tendon is the culmination of the two heads of the gastrocnemius and the soleus. The gastrocnemius origin is on the posterior distal femur; thus, it crosses the knee and the ankle. In quadrupeds (e.g., the horse or cheetah), a contracture of the Achilles tendon holds the calcaneus off the ground; the heel never touches the ground. Active extension of the knee automatically causes a passive plantarflexion of the ankle, which leads to efficiency when running. In humans, some of this evolutionary Achilles tightness is still present, such that gastrocnemius tightness is a common problem in many patients.

Furthermore, the gastrocnemius-soleus complex is so much larger than any other leg muscles that there is a constant imbalance, with a tendency to develop an equinus contracture, especially with prolonged nonweight bearing. Achilles stretching, especially of the gastrocnemius, is an important part of rehabilitation from most ankle injuries or surgeries.

Active contraction of the Achilles tendon results in plantarflexion through the ankle joint. This rotation is amplified across the rigid midfoot joints to the metatarsal heads, acting as a lever. (In other words, a centimeter of contraction in the Achilles tendon leads to several centimeters of plantarflexion at the metatarsal heads.) This is the key to efficient propulsion in human gait (Figure 52.2).

In the normal gait cycle, the posterior tibial tendon fires just before heel rise, inverting and locking the hindfoot and midfoot joints in a stable position, thus creating the rigid lever across the midfoot. If the posterior tibial tendon fails to lock the arch (as in posterior tibial tendon dysfunction), the midfoot remains flexible, and the Achilles contraction leads to progressive breakdown of the arch ligaments, with a progressive flatfoot deformity. Thus, a healthy posterior tibial tendon is essential to normal gait.

As the human foot accommodates uneven terrain, intermittent firing of the leg muscles keeps the leg vertical. In particular, the peroneal tendons, especially the peroneus brevis, prevents accidental inversion that might lead to a sprain. The peroneal tendons constantly work in response to input from the position sense receptors in the ankle joint, so that ankle stability is controlled somewhere below the level of the cerebral cortex.

Figure 52.2 Illustration of the midfoot. When the midfoot is rigid, the medial column acts as a rigid lever from the talus to the first metatarsal head. A relatively small magnitude of Achilles contraction is amplified to make a large amount of plantar flexion at the metatarsal head, through a “lever” effect. (Modified from LifeART image copyright (c) 2016, Lippincott Williams & Wilkins. All rights reserved.)

If the peroneal tendons and their balance reflexes are not functioning properly (such as when recovering from an injury or following a long period of immobilization), inversion injuries will occur. Rehabilitation of the ankle will require
strengthening of the peroneals and recovery of the position sense reflexes.

Principles of Rehabilitation

Immediately following an injury or surgery, the body reacts by initiating the inflammatory response. The first phase is the acute inflammatory phase, which usually lasts about 48 to 72 hours, but can be as long as 7 to 10 days. Damage to small blood and lymph vessels initiates a temporary vasoconstriction that lasts a couple of seconds to minutes. This is quickly followed by vasodilation and increased permeability, with an influx of blood, serum proteins, clotting factors, and platelets that make up the inflammatory exudate. What we see clinically is localized swelling, redness, pain, increased temperature, and loss of normal function.

The second phase of soft-tissue healing is the subacute migratory and proliferative phase, which typically lasts 10 days to about 6 weeks and overlaps the inflammation phase. The transition from debris removal to granulation tissue formation is a marker of proliferation and is necessary for scar tissue formation. Initially, the tensile strength of the wound matrix is low and is made up of type III collagen, but soon the weaker type III collagen begins to be replaced by a stronger type I collagen. Clinically, there is reduced erythema and swelling.

The third and final phase of soft-tissue healing is the remodeling phase, which can last anywhere from 6 weeks to 1 year depending on the degree of injury. During remodeling, the initial healing tissue converts to dense scar tissue, whereby the injured area becomes stabilized and restored. Clinically, this phase may initially be characterized by pain or soreness occurring after activity, but progresses toward pain-free function.

Although tendons, ligaments, muscles, articular cartilage, and bones show some variation in sequence and duration of events, all tissues follow the same general phases of soft-tissue healing. Thus, the same general intervention principles can be applied to most soft-tissue injuries of the foot and ankle. However, specific rehabilitation protocols must be followed after certain injuries and surgical procedures.

The timing of treatment after a foot and ankle injury is crucial, and should coincide directly with the various stages of healing and principles of weight-bearing progression. Just as the phases of soft-tissue healing overlap, the stages of rehabilitation should as well. Immediately after trauma to an injured body part, the primary goal is controlling pain and inflammation. Although some inflammation is necessary for healing, if not controlled, secondary injury can occur and lead to chronic inflammation. Initial treatment includes rest, protection, ice, compression, elevation, early motion, gentle manual therapy, medication, and therapeutic modalities.

A period of rest does not mean that the patient must be completely inactive. Rather, in order to avoid the harmful effects of immobilization, a period of “relative” rest is typically recommended. Most foot and ankle surgeons will rest and even immobilize the leg for a few days up to as long as 6 weeks following surgery. Once the tissues are rested and the wounds are healed, a patient can begin to initiate controlled activity. Be mindful that pain is a subjective response to injury and all people have a different pain threshold. It can be an extremely useful warning signal in most situations; therefore, use it to guide progression.

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