Although podiatrists commonly encounter plantar fasciitis, injuries to the lateral band of the fascia are less frequently diagnosed. These authors offer anatomical insights, pertinent diagnostic pearls and key tips on treatment options.
When we think of heel pain, we traditionally think of the anatomy, etiology and the symptomatology of “medial band plantar fasciitis,” and do not give much thought to the lateral band. However, injury to this band does exist both at the calcaneus and at the insertion point at the plantar aspect of the fifth metatarsal base. The symptomatology, etiology and treatments are different from traditional plantar fasciitis so proper evaluation and imaging are paramount for an accurate diagnosis.
There is a common misnomer regarding the actual anatomical structure called the plantar fascia. Is it a true fascial band or is it more of an aponeurosis, ligament or a band of connective tissue? True fascia has multiplanar, three-dimensional movement. While the plantar fascia moves slightly, it is mostly fixed to support and tether the forefoot to the rearfoot so as to support the medial and lateral columns of the foot. The main function of the plantar fascia is to support the foot from splaying proximal to distal due to its strength and fiber orientation. This is partly due to the windlass mechanism.
Hicks originally described the windlass or “cable” like structure of the plantar fascia and how it works to support the triangle orientation or “truss” of the foot. The top part of the truss is comprised of the calcaneus, midtarsal joint and the metatarsals. It is supported plantarly by the tension of the plantar fascia. This truss withstands the ground reactive forces pushing upward and the force downward from the body’s weight.1
Although we often think and describe the fascia to patients as one solid band, it does have three distinct sections. The medial and central bands originate from the larger medial calcaneal tubercle and fan forward toward the metatarsal heads and insert. The lateral band originates from the smaller lateral tubercle and fans distally to the plantar surface of the fifth metatarsal base. These fibers are distinct from the fibers of the peroneus brevis and the midtarsal ligaments in the area. The medial and central bands are cord-like and distinct. It is easy to recognize these bands with imaging modalities as the lateral band is thinner and flat.
Magnetic resonance imaging (MRI) and diagnostic ultrasound have correlated nicely for the medial and central band thickness figures. However, as the sagittal slices move laterally in the foot, MRI is less dependable for accuracy in regard to lateral band thickness. The lateral band is hard to measure due to the convex shape of the calcaneal tubercles and the oblique orientation of the band itself. Under normal circumstances, the proximal medial band measures between 3 and 3.5 mm, the central band measures 2.5 to 3 mm and the lateral band on ultrasound measures 1.7 to 2 mm thick.
Essential Biomechanical Insights
According to the literature as well as our clinical experience, the fascia that undergoes increased traction secondary to overpronation may predispose it to fascial irritation. The increased traction may also predispose the heel to the development of a spur (Wolff’s law).2 During the gait cycle, many things may alter the long arch. Prolonged foot
overpronation can be caused by internal and external factors such as structural/bony foot malalignment and a tight gastroc-soleus complex. This can also be caused by hip and lower extremity weakness.
The gluteus maximus and gluteus medius help to abduct, extend and externally rotate our lower extremity. Weakness in these areas will produce internal rotation of the lower extremity, driving the foot into a pronated, collapsed attitude. The posterior tibial and peroneus longus muscles are also important for maintaining arch height and arch mechanics so weakness or injury may predispose the patient to overpronation as well. These pronatory forces can place strain on the medial column and may tax the medial band of the plantar fascia. The typical biomechanical factors that predispose patients to medial band fasciitis are opposite of the elements that lead to lateral band fasciitis.
Unlike the traditional pronatory or valgus forces that cause medial band issues, supinatory forces may predispose a patient to lateral band fasciitis. These forces includes a cavovarus foot, a true calcaneal varus and a rearfoot varus or forefoot valgus deformity. Supinatory forces may come from: compensation during gait to offload medial foot pain; patients improperly using a motion control/straight lasted shoe; or an improperly varus posted orthotic.
What To Look For In The Physical Exam
Although the lateral calcaneal tubercle may be irritated and the band may be thickened at that insertion point, note that the fascia can be abnormally thickened and inflamed at the base of the fifth metatarsal as well. This area has long been associated only with the diagnosis of peroneus brevis tendonitis. Rarely do providers consider other diagnoses with these findings.
Lateral band insertion injury is real and more common than we realize. In addition to peroneus brevis tendonitis, other common differential diagnoses include sural nerve entrapment neuritis, adventitial bursitis, synovial cysts, os perineum irritation and enthesiopathies. Other differential diagnoses include nodules from autoimmune disorders, such as Crohn’s disease, reactive arthritis, rheumatoid arthritis, gout, etc.
Bear in mind that the symptoms of lateral fascia insertion pain mimic peroneus brevis insertional tendonitis. Patients usually present with chronic lateral foot pain, which is exacerbated by weightbearing. Often patients are unable to accurately locate the exact location of the pain and commonly point to the entire lateral aspect of the foot.
One will find that physical provocation of the peroneus brevis tendon insertion is unremarkable. However, extreme pain arises in response to direct plantar palpation and plantar lateral palpation at the fifth metatarsal base and styloid region. Resistance to eversion muscle testing of the peroneus brevis tendon provokes no pain. Patients often report severe post-static dyskinesia. Vague lateral column or radiating fifth ray pain may also be present. Swelling and ecchymosis are usually absent. Warmth is rare unless it is related to a rheumatological diagnosis.
The biomechanical foot evaluation typically presents with a supinated/varus position as mentioned above. Typically, one would refer patients with this symptomatology for diagnostic imaging to rule out peroneus brevis insertional pathology.
What You Should Know About Diagnostic Imaging
Diagnostic imaging of lateral band fasciitis may be challenging. Plain radiographs, which one usually obtains in the office, are typically unremarkable for pathology, although they are very important for biomechanical evaluation. After obtaining radiographs, it is common for most clinicians to pursue MRI or computed tomography (CT) scans. The CT scans are the best choice for ruling out a suspected fracture or other osseous abnormality one has identified on plain films.
Magnetic resonance imaging can help rule out soft tissue abnormalities. However, MRI examinations of the foot and ankle are commonly performed in standard orthogonal planes. The lateral fascial band’s oblique orientation from the lateral calcaneal tubercle to the fifth metatarsal base typically results in poor visualization when one obtains images in standard sagittal and axial orthogonal planes.
We suggest that digital ultrasound is the best modality for this condition as one can orient the transducer parallel to the long axis of the lateral band. This facilitates optimum visualization. Ultrasound can also calculate the thickness and identify echotexture changes characteristic of either an acute or chronic process. Normal tendon and ligament have a unique, striated appearance on ultrasound. This is referred to as a normal fibrillar echotexture. With an “-itis,” the tendon or ligament structure demonstrates increased caliber with maintenance of the fibrillar echotexture. With an “-osis,” the tendon or ligament structure demonstrates increased caliber with a breakdown of the normal fibrillar echotexture.
On MRI examinations, tendon and ligament structures appear as a black band-like structure with no signal. On ultrasound examinations, lateral band plantar fasciitis at the fifth metatarsal base appears as an abnormal increased caliber of the insertion typically with a significant loss of fibrillar echotexture. Intrasubstance deficits consistent with a partial tear are rare.
The base of the fifth metatarsal will occasionally show some minor signal changes on MRI consistent with stress reaction in the more chronic cases. Ultimately, however, diagnostic ultrasound is the modality of choice for this diagnosis. Although it is not the first choice for imaging major bony pathology, diagnostic ultrasound can pick up subtle calcifications and cortical bone defects such as erosions as well as early osteophytic changes typical of a chronic enthesiopathy. We agree that MRI or CT scan would be a secondary imaging choice for this condition unless one has a high index of suspicion for a fracture or tumor.
Exploring The Treatment Options
In regard to lateral band plantar fasciitis, treatment should include many of the traditional modalities we use for any musculoskeletal condition. However, ensuring adequate attention to the etiology is important. Supporting the medial arch with strapping, padding and varus posted orthotics as we do in traditional plantar fasciitis may backfire. Doing so will load the lateral foot and exacerbate the condition of lateral band plantar fasciitis. Choose a neutral shoe. If you are using an insert, first try a vertical or slight valgus post for the rearfoot prior to using a custom device.
If one is instituting injection therapy, a plantar lateral approach up into the base of the fifth metatarsal is best. Even with a seasoned technician, placement of the medication is tricky. One should direct the needle from plantar to dorsal into the fascial tissue at the base. Providers should feel the fibrous crunch with the tapping or needling technique into the fascia.
The choice of injection medication is clinician dependent. However, this is an area in which Traumeel homeopathic medication (Heel, Inc.) is useful, especially if a series of injections are warranted. Using a series of injections will initiate the inflammatory response and will eventually lead to collagen production from the cellular cascade, which is initiated by the microscopic needle trauma. Studies have reportedly shown that Traumeel promotes growth factors that stimulate proper tissue healing. For sensitive patients, infiltrating with lidocaine first to anesthetize the area may allow the clinician to needle the proper location for a slow, carefully placed injection.
When conservative treatment fails, transection of the lateral band at the fifth metatarsal base may be an effective treatment. We recall one case, in particular, in which the patient had received 18 months of conservative care that failed to resolve the patient’s symptoms. After the patient underwent transection of the lateral band at the fifth metatarsal base, all the symptoms resolved.
It is important that clinicians thoroughly evaluate patients for all possible causes of lateral band fascial injury, especially at the fifth metatarsal base. Diagnostic ultrasound has become more prominent in the podiatric community in recent years. It a viable and trusted imaging modality when it is performed by a seasoned examiner with state of the art equipment. We evaluate the movement of our podiatric patients via biomechanical analysis with many measures including walking and running. Accordingly, one should image functionally as well.
Ultrasound is a functional test that gives us the ability to see the collagen fiber alignment and the orientation of ligament, tendon and fascia in their respective planes of movement. It will also measure the thickness and echotexture as the tissue moves and one palpates it. Magnetic resonance imaging is static and is unable to rate this functionality or resolve the orientation of the collagen fibers of the tissues being imaged.
Dr. Schoene is a triple board certified sports medicine podiatrist and a certified athletic trainer. She is a fellow of the American Academy of Podiatric Sports Medicine and of the American College of Foot and Ankle Surgeons.
Dr. Kincaid is a full-time musculoskeletal ultrasonographer at 3T Imaging in Morton Grove, Ill., and Naperville Imaging Center in Naperville, Ill.
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