Ankylosing spondylitis (AS) is a chronic, inflammatory form of arthritis that primarily affects the spine, but its reach extends far beyond the vertebral column. As a systemic disease, AS can influence various joints and connective tissues throughout the body—including the feet. While spinal fusion and back pain are hallmark features, many individuals with AS experience debilitating foot symptoms that significantly impair mobility and quality of life. This essay explores the nature of AS, its pathophysiology, and the specific ways it affects the foot, including associated conditions like plantar fasciitis, Achilles tendonitis, and toe dactylitis.

What Is Ankylosing Spondylitis?

Ankylosing spondylitis is a type of spondyloarthritis, a group of inflammatory diseases that target the spine and, in some cases, peripheral joints. It is characterized by chronic inflammation, particularly at the entheses—the sites where tendons and ligaments attach to bones. Over time, this inflammation can lead to ankylosis, or fusion of the joints, resulting in reduced flexibility and mobility.

Key Features of AS:

• Chronic inflammation of the spine and sacroiliac joints
• Progressive stiffness and pain, especially in the lower back
• Fusion of vertebrae, leading to a rigid spine
• Peripheral joint involvement, including hips, shoulders, and feet
• Systemic symptoms, such as fatigue and eye inflammation (uveitis)

AS typically begins in early adulthood and is more common in males. Genetic factors, particularly the presence of the HLA-B27 gene, play a significant role in susceptibility.

How AS Affects the Foot

Although AS is most commonly associated with spinal issues, it can also affect the feet and ankles, leading to pain, stiffness, and structural changes. These symptoms arise due to inflammation in the joints and entheses of the foot, which can manifest in several distinct conditions.

Plantar Fasciitis

Plantar fasciitis is one of the most common foot-related complications in AS. The plantar fascia is a thick band of tissue that connects the heel bone to the base of the foot, supporting the arch and absorbing shock during movement.

AS-Related Plantar Fasciitis:

• Caused by enthesitis at the heel
• Results in sharp heel pain, especially during the first steps in the morning (“first-step pain”)
• Pain may improve with movement but worsen with prolonged activity
• Can affect one or both feet

This condition can severely limit walking and standing, making daily activities challenging for individuals with AS

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Achilles Tendonitis

The Achilles tendon, which connects the calf muscles to the heel bone, is another common site of inflammation in AS. Achilles tendonitis in AS is due to enthesitis at the tendon’s insertion point.

Symptoms:

• Pain and stiffness in the back of the heel and lower calf
• Swelling or lumps near the tendon
• Morning stiffness that improves with movement
• Pain during high-impact activities, such as running or jumping

Persistent inflammation can lead to tendon rupture, making early diagnosis and treatment crucial

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Toe Dactylitis (“Sausage Digits”)

Dactylitis refers to the swelling of an entire digit, often resembling a sausage. In AS, this occurs due to inflammation in the joints and entheses of the toes.

Features:

• Redness and swelling of one or more toes
• Pain and tenderness
• May affect multiple toes simultaneously
• Can be a sign of disease progression

Dactylitis is not only painful but also a visual indicator of systemic inflammation, prompting further medical evaluation

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Ankle Joint Involvement

Though less common than spinal symptoms, AS can affect the ankles, leading to joint pain, swelling, and reduced mobility.

Ankle Symptoms:

• Warmth and tenderness over the joint
• Swelling and stiffness, especially after rest
• Possible fusion of ankle bones in severe cases
• Changes in gait and posture due to pain

Imaging studies may reveal fusion in the midfoot, hindfoot, or ankle joints, which can severely impair walking

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Pathophysiology: Why the Feet Are Affected

The underlying mechanism of AS involves autoimmune inflammation targeting the entheses. Since the feet contain numerous entheses—especially around the heel and toes—they are particularly vulnerable.

Enthesitis in AS:

• Inflammation at tendon-bone junctions
• Leads to pain, swelling, and structural damage
• Common in Achilles tendon, plantar fascia, and toe joints

Over time, chronic enthesitis can result in calcification, bone fusion, and deformities, further complicating mobility.

Impact on Gait and Posture

Foot pain and stiffness from AS can alter the way individuals walk and stand. These compensatory changes may lead to:

• Muscle spasms or cramps
• Toe clawing for balance
• Altered gait, increasing strain on other joints
• Postural changes, exacerbating spinal symptoms

Such adaptations can create a vicious cycle of pain and dysfunction, affecting overall quality of life

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Diagnosis and Management

Diagnosis:

Diagnosing foot involvement in AS requires a combination of:

• Clinical examination
• Imaging (X-rays, MRI)
• Blood tests for inflammatory markers and HLA-B27

Treatment Options:

Managing foot symptoms in AS involves both medical and physical interventions:

Medications:

• NSAIDs (e.g., ibuprofen) to reduce inflammation
• Biologics (e.g., TNF inhibitors) for systemic control
• Steroid injections for localized relief

Physical Therapy:

• Stretching and strengthening exercises
• Orthotic devices to support arches and reduce strain
• Gait training to improve posture and mobility

Lifestyle Modifications:

• Weight management to reduce pressure on feet
• Low-impact activities like swimming or cycling
• Proper footwear with cushioning and arch support

Early intervention is key to preventing long-term damage and maintaining mobility.

Quality of Life Considerations

Foot involvement in AS can significantly affect daily functioning, mental health, and social participation. Studies show that individuals with AS report lower scores on foot health questionnaires, indicating a reduced quality of life

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Challenges Faced:

• Difficulty walking or standing for long periods
• Limitations in work and recreational activities
• Emotional distress due to chronic pain
• Social isolation from reduced mobility

Comprehensive care—including rheumatology, podiatry, and physical therapy—is essential to address these multifaceted challenges.

Ankylosing spondylitis is more than just a spinal disease—it’s a systemic condition that can profoundly affect the feet. From plantar fasciitis and Achilles tendonitis to toe dactylitis and ankle fusion, AS-related foot problems can be painful, disabling, and life-altering. Understanding these manifestations is crucial for timely diagnosis, effective treatment, and improved quality of life. With multidisciplinary care and proactive management, individuals with AS can maintain mobility and continue to lead fulfilling lives.

The human foot is a marvel of anatomical engineering, composed of 26 bones, 33 joints, and over 100 muscles, tendons, and ligaments. Among these bones lies the navicular, a boat-shaped bone in the midfoot that plays a crucial role in maintaining the arch and facilitating movement. However, in some individuals, an extra bone—known as the accessory navicular—appears adjacent to the navicular. Though often asymptomatic, this anatomical variation can sometimes lead to discomfort and functional issues, a condition known as Accessory Navicular Syndrome.

This essay explores the anatomy, types, causes, symptoms, diagnosis, and treatment of the accessory navicular, shedding light on a condition that affects a small but significant portion of the population.

Anatomy and Definition

The accessory navicular, also called os tibiale externum or os naviculare secundarium, is an extra bone or piece of cartilage located on the inner side of the foot, just above the arch. It is typically embedded within the posterior tibial tendon, which is responsible for supporting the arch and stabilizing the foot during movement.

This bone is congenital, meaning it is present from birth. It is not part of the standard skeletal structure and is found in approximately 2.5% to 10% of the population

. Most individuals with an accessory navicular are unaware of its presence unless it becomes symptomatic.

Types of Accessory Navicular

There are three distinct types of accessory navicular bones, each with unique anatomical characteristics and clinical implications:

Type	Description	Prevalence	Clinical Notes
Type 1	Small, round or oval sesamoid bone within the posterior tibial tendon; not connected to the navicular	~30%	Usually asymptomatic
Type 2	Heart-shaped or triangular bone (~12mm), connected to the navicular by cartilage	~55%	Most commonly symptomatic
Type 3	Fused to the navicular via a bony bridge, forming a horn-shaped structure	~15%	May cause structural issues

Type 2 and Type 3 are more likely to cause Accessory Navicular Syndrome, especially when subjected to trauma or repetitive stress.

Causes of Accessory Navicular Syndrome

While many people with an accessory navicular experience no symptoms, certain factors can trigger Accessory Navicular Syndrome, a painful condition resulting from irritation or inflammation of the bone and surrounding tissues.

Common Causes:

• Trauma: Sprains, falls, or direct impact to the foot can aggravate the accessory navicular.
• Overuse: Excessive physical activity, especially in athletes, can strain the posterior tibial tendon.
• Footwear: Poorly fitting shoes or those lacking arch support can rub against the bone.
• Flat Feet (Pes Planus): Individuals with flat feet place more stress on the posterior tibial tendon, increasing the risk of inflammation.

Signs and Symptoms

Symptoms of accessory navicular syndrome often emerge during adolescence, when the cartilage begins to ossify into bone. However, symptoms can also appear in adulthood, especially following injury or increased activity.

Typical Symptoms:

• Visible bump on the inner side of the foot, above the arch
• Redness and swelling around the bony prominence
• Pain or throbbing in the midfoot, especially during or after activity
• Tenderness when pressure is applied to the area
• Difficulty walking or wearing shoes due to discomfort

These symptoms can range from mild to severe and may interfere with daily activities or athletic performance.

Diagnosis

Diagnosing accessory navicular syndrome involves a combination of clinical examination and imaging studies.

Diagnostic Steps:

1. Physical Exam: The physician assesses the foot for swelling, tenderness, and structural abnormalities.
2. X-rays: Used to confirm the presence and type of accessory navicular.
3. MRI or CT Scan: May be ordered to evaluate soft tissue involvement, especially the posterior tibial tendon.

A thorough assessment also includes evaluating foot alignment, muscle strength, and gait mechanics, as these factors influence treatment decisions.

Treatment Options

Treatment for accessory navicular syndrome aims to relieve pain, reduce inflammation, and restore function. Most cases respond well to conservative management, though surgery may be necessary in persistent or severe cases.

Conservative Treatments:

• Immobilization: Using a cast or walking boot to rest the foot and reduce inflammation.
• Ice Therapy: Applying ice packs to the affected area to control swelling.
• NSAIDs: Medications like ibuprofen to alleviate pain and inflammation.
• Physical Therapy: Strengthening exercises and stretches to support the arch and improve tendon function.
• Orthotics: Custom arch supports or medial heel wedges to reduce pressure on the accessory navicular.

Surgical Intervention:

Surgery is considered when conservative treatments fail or symptoms recur frequently. The most common procedure is Kidner’s Procedure, which involves:

• Removing the accessory navicular
• Reattaching the posterior tibial tendon to the navicular bone

Post-surgical recovery typically includes immobilization, followed by physical therapy to regain strength and mobility.

Impact on Lifestyle and Activity

For athletes and active individuals, accessory navicular syndrome can be particularly disruptive. Pain and instability may limit participation in sports, especially those involving running, jumping, or lateral movements. Early diagnosis and appropriate treatment are essential to prevent long-term complications and maintain an active lifestyle.

With proper care, most individuals can return to normal activities without significant limitations. However, ongoing use of orthotics and attention to footwear may be necessary to prevent recurrence.

Psychological and Social Considerations

Chronic foot pain can affect more than just physical health—it may also impact mental well-being, self-esteem, and social participation, especially in adolescents. The visibility of the bony prominence and limitations in footwear choices can lead to self-consciousness. Supportive care, education, and reassurance are important components of holistic treatment.

Genetic and Developmental Aspects

The exact cause of accessory navicular formation is unknown, but there is evidence of a genetic predisposition. It is often bilateral (present in both feet) and may be inherited. Understanding the developmental timeline—from cartilage in infancy to ossified bone in adolescence—helps explain why symptoms often emerge during growth spurts.

Gait—the manner in which a person walks—is a complex biomechanical process involving coordinated movements of the muscles, bones, and joints. Subtle deviations in gait can reveal underlying musculoskeletal or neurological issues. One such deviation is the abductory twist, a phenomenon observed during the stance phase of walking. Though often overlooked, an abductory twist can be a key indicator of biomechanical dysfunction in the lower limb, particularly involving the foot and ankle.

Understanding Gait Mechanics

To appreciate what an abductory twist is, it’s important to understand the basic phases of gait:

1. Heel Strike: The heel contacts the ground.
2. Foot Flat: The entire foot makes contact as weight is transferred.
3. Midstance: The body passes over the stationary foot.
4. Heel Off: The heel lifts off the ground.
5. Toe Off: The toes push off to propel the body forward.

During these phases, the foot undergoes pronation (rolling inward) and supination (rolling outward) to absorb shock and adapt to the terrain. Ideally, the foot should transition smoothly from pronation to supination as it prepares for toe-off. However, when this transition is disrupted, compensatory movements may occur—one of which is the abductory twist.

What Is an Abductory Twist?

An abductory twist refers to a sudden outward movement (abduction) of the heel or foot during the toe-off phase of gait. It is typically observed as a quick lateral flick of the heel just before the foot leaves the ground. This motion is not part of normal gait mechanics and usually indicates that the foot is compensating for instability or misalignment elsewhere in the kinetic chain.

The twist is most noticeable when viewed from behind and is often seen in individuals with excessive pronation or poor foot control. It may also be accompanied by other signs of gait dysfunction, such as medial knee collapse or hip rotation.

Biomechanical Causes of Abductory Twist

Several biomechanical factors can contribute to the development of an abductory twist:

1. Excessive Pronation

When the foot rolls inward too much during midstance, it delays the transition to supination. As the body attempts to push off, the foot may twist outward to compensate for the lack of rigidity needed for propulsion.

2. Forefoot Varus

This structural deformity causes the front of the foot to tilt inward. To achieve ground contact during gait, the foot may overpronate, leading to an abductory twist during toe-off.

3. Weakness in Tibialis Posterior

The tibialis posterior muscle helps control pronation and stabilize the arch. Weakness or dysfunction in this muscle can result in poor foot control and compensatory twisting.

4. Hip and Pelvic Instability

Instability or weakness in the hips and pelvis can affect lower limb alignment. If the leg rotates inward excessively, the foot may twist outward during toe-off to maintain balance.

5. Tight Calf Muscles

Limited ankle dorsiflexion due to tight calves can alter gait mechanics, forcing the foot to twist outward to clear the ground.

Clinical Significance

An abductory twist is more than just a visual anomaly—it can be a sign of underlying pathology. Clinicians, especially podiatrists and physical therapists, use gait analysis to identify such compensations and determine their root causes. Left unaddressed, an abductory twist can lead to:

• Plantar fasciitis
• Achilles tendinopathy
• Medial knee pain
• Hip and lower back discomfort
• Increased risk of injury during sports or exercise

Recognizing and correcting the twist can improve gait efficiency, reduce pain, and prevent further complications.

Diagnosis and Assessment

Diagnosis typically involves:

• Visual Gait Analysis: Observing the patient walking barefoot from behind.
• Video Gait Analysis: Using slow-motion footage to detect subtle movements.
• Footwear Examination: Uneven wear patterns on shoes may indicate abnormal gait.
• Biomechanical Testing: Assessing foot structure, muscle strength, and joint mobility.

Treatment and Management

Treatment focuses on addressing the underlying cause of the abductory twist. Common interventions include:

1. Orthotics

Custom foot orthotics can correct structural imbalances, support the arch, and control excessive pronation.

2. Strengthening Exercises

Targeted exercises for the tibialis posterior, gluteal muscles, and core can improve stability and alignment.

3. Stretching

Stretching tight calf muscles and hip flexors can enhance mobility and reduce compensatory movements.

4. Footwear Modification

Supportive shoes with proper arch support and heel control can help manage gait abnormalities.

5. Manual Therapy

Physical therapists may use techniques to mobilize joints and release tight tissues contributing to poor gait mechanics.

Conclusion

An abductory twist during gait is a subtle yet significant indicator of biomechanical dysfunction in the lower limb. While it may seem minor, it often reflects deeper issues such as overpronation, muscle weakness, or structural deformities. Early recognition and targeted intervention can restore proper gait mechanics, alleviate pain, and prevent long-term complications. By understanding and addressing the abductory twist, clinicians and patients alike take a crucial step toward healthier movement and improved quality of life.

Chilblains are a reasonably common problem once the weather is cooler. These are a painful and itchy reaction of the smaller blood vessels in the toes to the variations in temperature. They result in a painful red area, which later becomes a dark blue color should they become chronic. Chilblains have just lately been receiving some extra press in the media as a result of them being more common in those infected with the coronovirus, being given the term, COVID toes.

Chilblains are a seasonal condition and appear in all places in which the climate gets cold enough to result in the reaction in the skin. An instance of PodChatLive had a deep discussion of the problem of chilblains:

The easiest method to manage chilblains is usually to prevent these by keeping the feet warm. If a chilblain will develop then it must be kept warm and be protected to stop the skin from breaking down. There are several chilblain creams which you can use to help to promote the blood circulation.

Severs disease or calcaneal apophysitis is a prevalent condition of the heel bone in developing children. At the back of the heel bone is a cartilage area that most of the development of the heel bone takes place at and this problem is an overuse injury of that cartilage area. It is more likely in kids that are active, are overweight and are taller. The typical signs of Severs disease is pain at the back and sides of the heel bone, primarily after sports activity. Severs disease is regarded as a self limiting problem, because the child will invariably at some point grow out of it as soon as growth of the heel pain stops and the developing region of cartilage inside the bone merges with the rest of the heel bone. That doesn’t suggest it shouldn’t be treated and may not be treated before that growth ceases.

This episode from PodChatLive was a comprehensive discussion into the issue of Sever’s disease/Calcaneal apophysitis:

A great way to take care of this problem can be managing the child’s and parent’s expectations and also lifestyle to help keep the signs and symptoms under control. The strains have to be managed via modifying and restricting activity levels. This is often challenging and may take some negotiation with the child. If the discomfort is severe after activity, then ice may be used to help relieve that. Often a cushioned heel insert might help protect the heel. Long term the prospects is good as they will grow out of this by the mid-teenage years.

Type two diabetes has become so common, it is almost as though we have become complacent regarding it. The incidence is rising in most places despite public health strategies are attempting to take care of the obesity crisis that is supporting the diabetes challenge. Diabetes has a number of complications that all combine collectively to put the feet at significant risk from complications. These complications vary from a mild infection to the more critical complications like a need to amputate a leg a result of a spreading infection or deceased tissue. The complications associated with diabetes have an effect on a wide variety of tissues in the body.

In relation to the feet, diabetes affects the blood supply and therefore any injury to the foot is more likely to be serious as there is insufficient good blood flow allowing healing to occur. Diabetes also damages the nerves, so that if there is some injury, either major or minor such as a blister, then no pain is felt, so the foot continues to be damaged resulting in the complication a great deal more severe. The body has numerous functions to fight infection, but in diabetes the response to an infection is much more sluggish than in those without diabetes. Diabetes can also affect the eye and while the eyes are a long way from the foot, ample vision is needed to see any issues that may have occurred to the foot so it may be dealt with. Even the renal disease that frequently occurs in diabetes impacts wound healing after the injury has been done and the presence of disease in the kidney can affect what medicines, for example antibiotics, may be used and sometimes that range can be quite restricted.

It is for all these complications, and others not brought up, that those with diabetes have to take additional care of their feet. They need to check them routinely to make sure that there is no injury and if there is an injury they must get medical help quickly. Most importantly, they must be regularly managed by a foot doctor.