When it comes to ankle injuries, the rehabilitation program must account for the entire range of functions of this multifaceted joint.
By Dan Cipriani
Dan Cipriani, MEd, PT, is Assistant Professor in the Department of Physical Therapy at the Medical College of Ohio. He is a frequent contributor to Training and Conditioning.
Injuries to the foot and ankle are among the leading causes of lost playing time in athletics. In severe cases, long-term disability may result. This obviously makes prevention the ultimate goal in lower leg care. However, even with the best plans for prevention, ankle injuries will still occur.
The spectrum of ankle injuries includes a range of mild to moderate sprains, fractures, dislocations, tendinitis, and tendon ruptures. And no two ankle injuries are the same--an Achilles tendon tear is very different from a fracture or a dislocation.
Luckily, however, several common denominators exist in terms of foot/ankle rehabilitation. These common factors include reclaiming "normal" muscle and joint function as well as restoring "normal" proprioception and reaction time, allowing for a fairly general ankle rehabilitation and sports preparation program to be profiled in this article.
THE EVALUATION
Understanding the nature of a foot/ankle injury is essential to the design of the rehabilitation program. Therefore, a complete evaluation of the lower extremity to determine the extent of functional loss should be performed. This evaluation must include several areas: an examination of both the strength and range-of-motion of the foot/ankle joint, and the effects of the injury on the rest of the leg, particularly the knee and hip.
At the foot and ankle, evaluation of range of motion (ROM) should be performed in both non-weightbearing and weightbearing positions (provided the athlete is able to bear weight). The non-weightbearing evaluation lets the examiner feel the limited motion, which helps to identify what tissue/structure may be injured. The weightbearing ROM assessment is related more to function. It allows the examiner to observe compensations at the knee or hip as a result of the injury, compensations that may be missed in a non-weightbearing evaluation. In general, the weightbearing ROM will be greater than the non-weightbearing ROM.
Assessing the functional strength of the foot/ankle is the next step. However, the available measurement tools for this evaluation are problematic. While the traditional manual muscle test (MMT) is an effective tool to assist in the evaluation of significant strength deficits, it unfortunately does not accurately predict muscle function for walking and running.
The dilemma then arises of how to evaluate an athlete's functional limitations related to weightbearing activities, while he or she may not yet be able to tolerate even unassisted walking. Recently, some clinicians have begun investigating partial weightbearing devices for such an assessment; so far this appears to be an effective method, but more research needs to be done.
Regardless of the strength status of the foot/ankle following injury, it is important to understand lower-leg musculature as it relates to the entire leg. One piece of recent research suggests that the function of the lower leg is intimately related to the strength and function of the muscles of the hip; individuals with acute ankle injuries were shown to have significant strength deficits in the hip muscles. Research has also shown that muscle function is significantly affected following even the mildest of ankle sprains; reaction time in the lower leg becomes slower following sprains and strains, leaving the athlete more susceptible to re-injury. These factors must be addressed appropriately during rehabilitation.
FOOT/ANKLE KINEMATICS
The ankle joint and subtalar joint in particular have a significant influence on the functions of the knee and hip during all weightbearing activities. Recognizing these influences will assist the clinician in not only understanding the functional limitations of the injured athlete, but also in designing a comprehensive, function-specific rehabilitation program.
The Ankle Joint: The ankle, or talocular, joint is considered to be a modified hinge joint, allowing dorsiflexion and plantarflexion in the sagittal plane; however, the nature of the ankle also allows for some movement to occur across the frontal and transverse planes as well. As the ankle moves through full dorsiflexion, the foot will also move into slight eversion and abduction. This is important to keep in mind during the rehabilitation phase; in order to facilitate ankle dorsiflexion ROM, slight amounts of eversion/abduction also need to occur.
Ankle dorsiflexion is more important functionally for gait than plantarflexion. During walking and running, an individual will use most of the available dorsiflexion ROM, while an individual will use only about 50 percent of the available plantarflexion range.
It is also important to understand the position of the ankle and degrees of flexion during gait. During walking and running the ankle is in a position of slight dorsiflexion (or neutral) at initial contact. It immediately passively plantarflexes through foot flat. During midstance, the ankle moves into its greatest dorsiflexion, reaching 10 to 15 degrees just prior to heel off. From heel off through toe off, the ankle again plantarflexes, actively this time, from the range of 15 degrees of dorsiflexion to approximately 20 degrees of plantarflexion.
In addition, the motion of ankle dorsiflexion also creates a mild separation at the distal tibial-fibular articulation. In the event of a "high ankle sprain," a traumatic separation of the distal tib-fib joint, the healing time of the anterior and posterior tib-fib ligaments will dictate the athlete's return to function.
Clinically, the use of temporary heel lifts may be useful early on to maximize the range of dorsiflexion during weightbearing activities. Heel lifts may serve to place the ankle in relative plantarflexion, preventing the ankle from reaching end-range dorsiflexion, and thus minimizing stress to the tib-fib joint.
Subtalar Joint: Motion in the frontal plane occurs predominantly at the subtalar joint. This motion is measured by the movements of the calcaneus from an inverted to an everted position. Although the subtalar joint has nearly twice as much inversion ROM available compared with eversion, it is the eversion that is functionally more important. Individuals tend to use most or all of the available eversion ROM available during walking and running. Inversion ROM is approached only in injury states, such as with lateral ankle sprains (inversion sprains).
During walking and running, the subtalar joint will move quickly and forcefully through its fullest available range of calcaneal eversion (which represents pronation). This motion is imperative as it "unlocks" the rest of the foot for shock attenuation and surface accommodation. Pronation at the subtalar joint also directs the tibia into slight internal rotation at initial contact; internal tibial rotation allows the knee to "unlock" as well as to absorb shock by flexing slightly. Thus, pronation at the foot unlocks not only the forefoot but also the knee.
The motion of inversion at the subtalar joint occurs during the latter portion of midstance of gait--and actually, this inversion is simply the act of moving out of full eversion. It is not until heel off that the subtalar joint approaches an inverted position (supination). This supination is a result of the entire lower leg moving through an external rotation as the body advances over the fixed foot. As the lower leg externally rotates, the tibia forces the talus to externally rotate, which in turn forces the calcaneus to invert--or supinate.
Inversion and eversion at the subtalar joint also play a role in the rehabilitation progression following ankle sprains. For example, an athlete with an eversion sprain (medial ankle sprain involving the deltoid ligament complex) will need to be progressed gradually into weightbearing--full weightbearing will place the greatest stress on the healing ligaments because of the normal motion of pronation at the subtalar joint. On the other hand, athletes with inversion sprains can be progressed very aggressively with full weightbearing--end range inversion is never approached with walking and running, and thus the lateral ankle ligaments are less likely to be stressed during weightbearing activities.
MUSCLE FUNCTION
and REHABILITATION
Muscles and their proprioceptors play a major role in the integrated function of the ankle joint, subtalar joint, and the entire leg during walking and running. Therefore, it is imperative that the clinician keep in mind the true function of each of the muscles as they pertain to weightbearing activities.
However, a review of lower-extremity muscle function during gait in the standard anatomy text does not necessarily suffice. For example, although the gluteus medius may be depicted as a hip abductor, its function during gait is very different. During gait the stance-side gluteus medius works eccentrically to stabilize the pelvis in the frontal plane. In fact, it is most active while the hip is in a position of ADDuction, as the pelvis dips in the frontal plane on the non-stance side. Rehabilitating the gluteus medius based on an anatomy text definition will lead the clinician to perform sidelying hip abduction exercises. These will certainly increase strength of the gluteus medius, however, they will not challenge the muscles to work in functional mode.
Another example: a traditional exercise for strengthening the gastroc-soleus muscle group is the "calf raise." This exercise consists of the athlete standing and raising up on the balls of his or her feet and slowly returning. Resistance in the form of free weights or a machine is sometimes added.
This exercise is certainly an effective means to train the gastroc-soleus concentrically and eccentrically at the ankle. However, a significant shortcoming of this exercise is the range of motion in which it is performed--typically the athlete will stand in a neutral position, rise up on the balls of the feet, move into full plantarflexion, and then return to neutral. As mentioned above, the ankle joint actually begins moving from a position of 10 to 15 degrees of dorsiflexion and ends in partial plantarflexion. The movement into dorsiflexion during midstance is controlled eccentrically by the posterior calf group, and the concentric contraction of these same muscles begins while the ankle is still in maximum dorsiflexion.
To remedy the above exercise, a function-specific exercise that could be added would be the Lunge-Plus exercise. Using the right leg as the exercising leg, the athlete performs a traditional lunge, advancing forward with the left leg. Just prior to making ground contact with the left foot, the athlete is instructed to plantarflex the right foot, which essentially accelerates the lunging leg forward. This exercise provides a brief eccentric component during the early lunge movement, followed by a concentric contraction at the end of the movement--similar to the reactions during running.
Another issue to consider is how the muscles of the hip assist the foot and ankle. For example, the lateral rotators of the hip contract eccentrically during the pronation phase of gait (initial contact through foot flat) to decelerate the internal rotation forces occurring as a result of subtalar joint pronation (tibial internal rotation followed by femoral internal rotation). During the supination phase, the lateral rotators work concentrically to assist with propulsion through supination. Thus the muscles of the hip play a vital part in the normal function of the foot/ankle during weightbearing activities.
The bottom line in terms of foot and ankle rehabilitation is that the clinician must be aware of the actual functional demands of the muscles and joints, and the subsequent rehabilitation program must be based on these demands. Along the same lines, exercise specificity plays a major role in the effectiveness of every rehabilitation program. Lower-extremity exercises must take into account the special needs of each joint and muscle group, as well as consider the joints and muscles proximal/distal that contribute to normal function.
Isolation exercises, those that address a single muscle or joint as it acts in a single plane, are very useful to specifically target a "weak link." However, the clinician must also find or create exercises that will challenge the specific function of lower extremity. Lower-extremity exercises must be evaluated to determine if each exercise addresses the unique functions of a particular joint, muscle, or integrated joint/muscle-group activity.
CONCLUSION
In terms of functional returns, two analogies must always be kept in mind. Number one, any chain is only as strong as its weakest link. Number two, a weak team member will put additional stress on the rest of the team.
If the ankle is the weak or limited member of the lower-extremity "team," even the strongest athlete will be impeded. Even if the hip and knee are 100 percent, a weak (or a proprioceptively deficient) ankle will determine his or her performance level. Also, if the ankle is weak or limited in motion, the hip and knees may take on additional stresses to compensate. Thus, a proprioceptive deficiency at the ankle (or a weakness at the ankle) can put the remainder of the lower extremity at risk of injury.
With this in mind, the clinician is advised to consider an injury to the foot/ankle as an injury that truly affects the entire lower extremity. Only with a thorough non-weightbearing and weightbearing evaluation will these potential complications become evident. With a sound appreciation of gait, and the motions and forces at the foot, ankle, knee, and hip, the clinician will be able to design a functionally sound rehabilitation program to fit into the tissue's healing time-frame.