Sesamoid Arthritis: Causes, Symptoms, Diagnosis, and Treatment

What is Sesamoid Arthritis?

Sesamoid arthritis is a degenerative joint condition characterized by the breakdown of cartilage and inflammation within or around the sesamoid bones, typically located beneath the big toe joint, leading to pain, stiffness, and reduced function.

Understanding Sesamoid Bones

Sesamoid bones are small, independent bones embedded within a tendon where it passes over a joint. Unlike most bones, they are not directly connected to other bones via a joint but rather suspended within soft tissue. Their primary function is to act as a pulley, providing a smooth surface for the tendon to slide over, thereby increasing the mechanical advantage and leverage of the muscles. The most well-known sesamoid bone is the patella (kneecap).

In the foot, there are typically two pea-sized sesamoid bones located side-by-side beneath the head of the first metatarsal bone, connected to the flexor hallucis brevis tendon, which helps control the big toe (hallux). These tiny bones play a crucial role in weight-bearing, propulsion during walking and running, and protecting the flexor hallucis longus tendon as it passes to the big toe.

What is Arthritis?

Arthritis is a broad term encompassing over 100 conditions that involve inflammation of one or more joints. It typically causes pain, swelling, stiffness, and reduced range of motion. The most common forms include osteoarthritis (degenerative, "wear-and-tear" arthritis) and rheumatoid arthritis (an autoimmune inflammatory condition). While the specific mechanisms differ, both involve damage to the articular cartilage, the smooth, slippery tissue that covers the ends of bones in a joint, allowing them to glide effortlessly.

Defining Sesamoid Arthritis

Sesamoid arthritis specifically refers to the inflammation and degeneration of the cartilage surrounding one or both of the sesamoid bones in the foot, or the joint formed between the sesamoid bones and the first metatarsal head. This condition is a form of osteoarthritis affecting these small, vital bones. It differs from sesamoiditis, which is primarily an inflammation of the sesamoid bones and their surrounding tendons without significant cartilage damage, and sesamoid fracture, which is a break in the bone itself. While sesamoiditis and fractures can sometimes predispose one to sesamoid arthritis over time due to altered biomechanics or chronic inflammation, arthritis implies a more chronic degenerative process of the joint surface.

Causes and Risk Factors

Sesamoid arthritis often arises from a combination of mechanical stress, trauma, and underlying joint health.

• Overuse and Repetitive Stress: Activities that involve repetitive pressure or impact on the ball of the foot, such as running, jumping, dancing (especially ballet), basketball, and soccer, can lead to chronic microtrauma and accelerate cartilage wear.
• Biomechanical Factors:
  • Foot Structure: Individuals with high arches (pes cavus) or, less commonly, flat feet (pes planus) may experience altered pressure distribution under the forefoot.
  • Gait Abnormalities: Imbalances in walking or running patterns can place undue stress on the sesamoids.
  • Hallux Valgus (Bunions): This common deformity of the big toe joint can alter the alignment and function of the sesamoids, leading to increased friction and wear.
• Improper Footwear:
  • Lack of Support: Shoes without adequate cushioning or arch support.
  • High Heels: Shift excessive weight onto the forefoot.
  • Narrow Toe Boxes: Compress the forefoot and big toe, increasing pressure on the sesamoids.
• Trauma: A direct impact or sudden, forceful dorsiflexion (bending upwards) of the big toe can injure the sesamoids or the surrounding joint, potentially initiating or exacerbating arthritic changes.
• Systemic Inflammatory Conditions: While less common than osteoarthritis, sesamoid bones can be affected by systemic inflammatory arthritides like rheumatoid arthritis, psoriatic arthritis, or gout, which cause widespread joint inflammation.
• Age: As with other forms of osteoarthritis, the risk generally increases with age due to cumulative wear and tear on the cartilage.

Signs and Symptoms

The symptoms of sesamoid arthritis typically develop gradually and worsen over time.

• Pain: The hallmark symptom is persistent pain localized to the ball of the foot, directly beneath the big toe joint. This pain is often described as a dull ache, but can be sharp or throbbing, especially during weight-bearing activities or toe push-off.
• Swelling: Noticeable swelling around the ball of the foot, particularly on the plantar (bottom) aspect.
• Stiffness: Difficulty and pain when bending or extending the big toe, especially after periods of rest or in the morning.
• Tenderness: The area around the sesamoid bones is typically tender to touch or direct pressure.
• Limited Range of Motion: A noticeable decrease in the ability to move the big toe joint through its full range of motion.
• Clicking or Grinding Sensation (Crepitus): Some individuals may feel or hear a clicking, popping, or grinding sensation when moving the big toe, indicating roughened joint surfaces.
• Altered Gait: To avoid pain, individuals may unconsciously alter their walking pattern, leading to compensatory issues in other parts of the foot, ankle, or even knee.

Diagnosis

Diagnosing sesamoid arthritis involves a thorough clinical evaluation combined with imaging studies to differentiate it from other forefoot conditions.

• Clinical Examination:

  • History Taking: The physician will inquire about the onset, nature, and aggravating/alleviating factors of the pain.
  • Physical Assessment: This includes palpating the sesamoid area for tenderness, assessing the range of motion of the big toe joint, and observing the foot's overall structure and gait. Specific tests, such as stressing the big toe joint, may reproduce pain.

• Imaging Studies:

  • X-rays: Weight-bearing X-rays are typically the first line of imaging. They can reveal signs of arthritis such as joint space narrowing (indicating cartilage loss), subchondral sclerosis (increased bone density beneath the cartilage), osteophytes (bone spurs), and cysts. Comparison views of the unaffected foot may also be helpful.
  • Magnetic Resonance Imaging (MRI): An MRI provides detailed images of soft tissues, including cartilage, tendons, and ligaments. It can show the extent of cartilage damage, inflammation, bone marrow edema (swelling within the bone), and can help rule out other conditions like stress fractures or avascular necrosis (death of bone tissue due to lack of blood supply) of the sesamoids.
  • Bone Scan: In some cases, a bone scan may be used to identify areas of increased metabolic activity, suggesting inflammation or stress reactions in the sesamoids.

• Differential Diagnosis: It's crucial to distinguish sesamoid arthritis from other conditions presenting with similar symptoms, including sesamoiditis, sesamoid fracture, turf toe (ligamentous injury to the big toe joint), gout, or Freiberg's disease (osteochondrosis of the metatarsal head).

Management and Treatment Strategies

Treatment for sesamoid arthritis typically begins with conservative approaches aimed at reducing pain, inflammation, and protecting the joint. Surgical intervention is reserved for cases that do not respond to conservative measures.

Conservative Approaches

• Rest and Activity Modification: Reducing or temporarily stopping activities that aggravate the pain is crucial. This may involve switching to low-impact exercises like swimming or cycling.
• Ice and Elevation: Applying ice packs to the affected area for 15-20 minutes several times a day can help reduce pain and swelling. Elevating the foot can also assist.
• Anti-Inflammatory Medication (NSAIDs): Over-the-counter non-steroidal anti-inflammatory drugs like ibuprofen or naproxen can help manage pain and inflammation. Prescription-strength NSAIDs may be used for more severe cases.
• Footwear Modifications:
  • Stiff-Soled Shoes: Shoes with rigid soles, or even a rocker-bottom sole, reduce motion at the big toe joint, thereby minimizing stress on the sesamoids.
  • Wide Toe Box: To prevent compression of the forefoot.
  • Low Heels: To reduce forefoot pressure.
• Orthotics and Padding:
  • Custom or Over-the-Counter Orthotics: Can help redistribute pressure away from the sesamoid area.
  • Metatarsal Pads or Bars: Placed behind the ball of the foot, these can lift and offload pressure from the sesamoids.
  • Sesamoid Offloading Pads: Specific cut-out pads designed to relieve direct pressure on the sesamoids.
• Physical Therapy: A physical therapist can provide a tailored program including:
  • Manual Therapy: Joint mobilization to improve big toe range of motion.
  • Strengthening Exercises: For intrinsic foot muscles and muscles of the lower leg to improve foot stability and mechanics.
  • Stretching: For tight calf muscles or Achilles tendon, which can influence forefoot pressure.
  • Gait Retraining: To correct biomechanical inefficiencies that contribute to sesamoid stress.
  • Modalities: Ultrasound or electrical stimulation may be used to reduce pain and inflammation.
• Injections:
  • Corticosteroid Injections: Can provide temporary relief by reducing inflammation directly in the joint. However, repeated injections are generally avoided due to potential side effects like tendon weakening or fat pad atrophy.
  • Hyaluronic Acid Injections (Viscosupplementation): While more commonly used in larger joints like the knee, these may be considered to improve joint lubrication and cushioning in selected cases.

Surgical Intervention

Surgery is typically considered only after conservative treatments have failed to provide adequate relief for at least 6-12 months and the pain significantly impacts daily activities.

• Sesamoidectomy: The surgical removal of one or both sesamoid bones. This is a common procedure for chronic sesamoid pain, but it can alter foot biomechanics, potentially leading to big toe deviation or transfer metatarsalgia (pain in other metatarsal heads).
• Cheilectomy: If bone spurs are the primary issue limiting motion and causing pain, they can be surgically removed to decompress the joint.
• Arthrodesis (Fusion): In very severe, debilitating cases of MTP joint arthritis involving the sesamoids, fusion of the big toe joint may be considered. This eliminates motion at the joint but provides significant pain relief and stability.

Prevention and Long-Term Management

While not always entirely preventable, several strategies can help reduce the risk and manage the long-term effects of sesamoid arthritis.

• Appropriate Footwear: Consistently wearing shoes with good cushioning, arch support, a wide toe box, and a stiff sole (or rocker bottom) is paramount for daily activities and exercise. Avoid high heels and excessively flexible shoes.
• Gradual Increase in Activity: When starting new exercise programs or increasing training intensity, do so gradually to allow the body, including the foot structures, to adapt.
• Proper Biomechanics: Work with a physical therapist or podiatrist to identify and correct any gait abnormalities or muscular imbalances that place undue stress on the forefoot.
• Warm-up and Cool-down: Always perform a proper warm-up before exercise and a cool-down afterward to prepare and recover the joints and muscles.
• Listen to Your Body: Pay attention to early signs of pain or discomfort in the ball of the foot. Early intervention can prevent the progression of symptoms and joint damage.
• Weight Management: Maintaining a healthy body weight reduces the overall load and stress on the foot and ankle joints, including the sesamoids.
• Regular Foot Care: Routine self-checks for tenderness, swelling, or changes in foot shape can help in early detection.