What Are Sesamoid Bones in the Foot?
One of the potential causes of foot pain in runners and and athletes is sesamoiditis. Sesamoiditis is inflammation of the sesamoid bones.
Sesamoids are bones which are embedded within a tendon to increase mechanical efficiency. You have several sesamoids in your body. The largest and best-known of these is knee cap or “patella.”
The patella is a roundish bone that is embedded within the patellar tendon. The external surface of the knee cap is covered with the tendon that crosses the knee connecting the powerful thigh muscles to the shin bone. The internal surface of the knee cap is covered with cartilage. The cartilage helps the knee cap glide easily and decrease strain at the knee.
Under each big toe joint, in the ball of the foot, you have two little sesamoid bones sitting side by side. They are about the size of black beans. The one that is closest to the little toe is called the fibular sesamoid. The other is called the tibial sesamoid.
Both of the sesamoids are embedded within the flexor hallucis longus (FHL) tendon. Like the knee cap, they are also covered with cartilage that helps them (and the FHL tendon) glide when you walk and bend your big toe joint.
The sesamoid bones tolerate an incredible amount of stress. When you walk, about 50% of all your body weight is transmitted through the big toe joint. That means that about one quarter of all your weight is supported on a little bone about the size of a black bean gliding along the bottom of the first metatarsal bone as you push off at the ball of the foot.
What Causes Sesamoiditis?
When too much stress is applied to the sesamoids they can become irritated, painful and inflamed, a condition known as sesamoiditis. In the mild cases, sesamoiditis is really a form of tendinitis because it is the FHL tendon that is irritated. But if you continue to apply the same offending force to the big toe joint the condition can become much more serious. In some cases they can even fracture. A cracked or broken sesamoid is a serious problem because they are very difficult to heal.
Too much bending of the big toe joint can cause sesamoiditis. If you spend a a great deal of time kneeling, which forces the big toe to bend upward(dorsiflexion) you can stretch the FHL tenon and causes FHL tendonitis or mild sesamoiditis. A common cause of this is taking on a weekend home improvement project like installing a new tile floor.
Trauma to the big toe joint can also cause sesamoiditis. Jumping of a ladder on a hard surface can cause a contusion (or bruise) of the articular cartilage covering the sesamoid bone. Repeatedly traumatizing the sesamoids by walking on a treadmill at a steep angle can do the same thing. Although the force is less with each motion, the cumulative stress can have the same result. Elliptical trainers and treadmills cracked up at a steep ankle force the big toe upward, dramatically increases stress to the sesamoid bones.
In triathletes I more often see sesamoiditis causes by stiff, poorly fitting cycling shoes. In training for an Ironman or 70.3 triathlon, the increased cycling volume results in a repetitive stress type irritation and injury to the sesamoids. This is often easily corrected with new cycling shoes, custom cycling orthotics or a professional bike fit session.
Sesamoiditis Caused by Running
The most common causes of sesamoiditis I see are rapidly increasing running mileage and running steep hills. This is usually in those training for their first marathon. I don’t see it nearly as often in seasoned marathon runners.
Part of this may be that the newbie marathon runner is strengthening many structures all at the same time. The experienced runner typically has better developed neuromuscular connections that allow for better biomechanical efficiency and less stress to joint supporting structures like the sesamoid bones in the foot.
When you are training for a marathon, you are applying rapidly increasing loads to the bones, muscles, tendons and ligaments. The muscles are sore and limit your training at the beginning, but they rapidly gain strength. The bones and ligament (upon which the muscles apply their force) don’t strengthen nearly as quickly.
At some point your muscles get strong enough to actually cause tiny little tears in the tendons (known as tendinitis) or cracks in the bone (known as stress fractures). When this happens to the FHL tendon and/or sesamoids in the foot you get sesamoiditis.
Hill repeats are one of the most effective tools a runner can use to increase strength and power. However hill repeats put a ridiculous load on the ball of the foot. Most of the marathon runners I see with sesamoiditis have been doing hill repeats regularly for about a month.
My theory is that 1) experienced runners are more biomechanically efficient and less likely to to injury the sesamoids with hill training and 2) the experienced runner is much more adept to listening to his/her body. If you have never run long distances you may have a tougher time discerning acceptable muscle soreness from unacceptable joint and tendon tenderness.
What is a Sesamoid Stress Fracture?
A stress fracture is a tiny hairline crack a bone. This often happens from repetitive stress such as rapidly increasing running distance too quickly. You and your podiatrist cannot see a stress fracture on x-ray when it first starts to hurt. Stress fractures only become visible after your body has tried to heal it. A sesamoid stress fracture may be visible anywhere from 2 weeks to 12 weeks after it becomes injured. X-rays ore notoriously unreliable. Just because you can’t see it on an x-ray doesn’t mean it isn’t broken. MRI is a much more effective way to diagnose a sesamoid stress fracture. MRI can show a stress fracture even in its earliest stages.
How to Tell if You Have Sesamoiditis
Self-diagnosing of sesmoiditis is fairly simple. Lightly press the bottom of the big toe joint with one finger until you fell the hard little sesamoid bones. Press lightly and see if one hurts more than the other. If one is way more tender than the other you will know which one is inflamed.
If they are both similarly tender and the sesamoid bones hurt even more when you pull the big toe as far upward as it will go (to the end range of motion), it may be more FHL tendinitis than a true sesamoid injury. If one is exquisitely tender when you press on it, the possibility of a sesamoid stress fracture or broken sesamoid bone becomes seems more likely.
How Foot Doctors Diagnose Sesamoiditis
If your see a sports medicine foot specialists, the doctor will take a full history of the injury, perform a physical diagnosis take x-rays and determine the exact cause of the injury and pain. If there is question of a sesamoid stress fracture he may order an MRI of the foot.
How to Cure Sesamoiditis
Sesamoiditis is treated based on the extent of injury. The main point is that it must be taken seriously. Sesamoiditis that is under-treated or ignored may get significantly worse leading to a broken sesamoid bone, arthritis of the sesamoid bone, surgery, chronic pain and permanently altered biomechanics. In the worse cases a condition known as “sick-sesamoid-syndrome” develops and leads to a sesamoid bone that has to be surgically removed. This is not good. If you remove one sesamoid bone, the other can become arthritic, the big toe can drift left or right causing a bunion or other deformity to develop.
Stop the Activity that Caused the Sesamoiditis
This may seem obvious, but if you got sesamoiditis while you have been running hills...stop. If you have been walking on a treadmill with it cranked up at a steep angle...stop. If you started to get pain in the sesamoids while using an elliptical trainer…(you guessed it)...stop! Try to avoid anything that forces you to stand up on the toes or forcibly bend the big toe up.
One of the simplest ways to relieve irritation and pressure to the sesamoids is with a “dancer’s pad.” This is a felt or gel pad that has a cu-out under the big toe joint. The idea id to move the pressure away from the sesamoid bones and transfer it to the ball of the foot under the second, third and fourth metatarsal heads. If padded correctly, this can allow the inflammation to decrease and the sesamoiditis will heal.
The semamaids are stressed most at the end range of extension at the big toe joint (bending the toe all the way upward) when you walk. By taping the big toe to limit this motion, you can transfer some of that stress to the tape and help heal the sesamoids. When performing sesamoid taping, the best type of tape called “elastoplast” or “tenoplast.” IT is strong, very adhesive and has a slight stretch.
The best shoes for sesamoiditis are very stiff and have a rocker sole. Dansko clogs are probably the best example of the ideal shoe to decrease the load to the sesamoid bones. Because clogs are so stiff, the big toe doesn’t bend when you walk. In addition the forefoot or sole is curved so that your foot actually rolls and further decreases pressure to the ball of the foot. Wearing these the right shoes is sometimes enogh to allow the sesmoiditis to heal on its own.
Sesamoiditis Steroid Injections
Corticosteroids are the very best way to stop the inflammation that causes pain from arthritis, tendinitis or even sesamoiditis. But steroid injections come with a price. Corticosteroids are great at breaking up collagen bonds. If the goal is to stop pain and get back in the game, that is a good thing. If you are trying to break up scar tissue, this is a good thing. If you happen to have tears in the FHL tendon (made of up of highly organized collagen fibers) or a bruise in the articular cartilage, that is a bad thing. The problem can become much worse. Steroid injections should only be used with the intent of breaking up a chronic cycle of inflammation. They don’t really “cure” anything.
Sesamoiditis Supartz and Synvisc Injections
If the sesamoids have been injured for a long time and you have developed arthritis sesamoids, hyaluronic acid injection may help. Supartz and Synvisc are the two types. They are both FDA approved to treat arthritis of the knee, but sports medicine specialists who treat runners and triathletes often use these in arthritic ankles and big toe joints. Theses injections serve as a joint lubricant and are a more natural alternative to steroid injections.
Sesamoiditis and Platelet Rich Plasma (PRP) Injections
If the sesamoiditis is really just micro-tearing to the FHL tendon instead of a real injury to the sesamoid bone or sesamoid cartilage, it is possible to induce healing through a PRP injection. A PRP injection uses your bodies own cells to stimulate new capillary formation in an injured tendon, and rapidly repair a tendon that has been chronically injured.
Advanced Treatments to Rapidly Heal Sesamoiditis
A bone stimulator is one of the most effective methods to heal a stress fracture or completely broken sesamoid. As long as the crack is small and the pieces of bone haven’t moved apart a bone stimulator can help you body form bone and heal the fracture faster.
When Sesamoiditis and Sesamoid Fractures Needs Surgery
If the fracture is “displaced” (meaning that that broken pieces have moved apart) surgery may be necessary to put the pieces back together using surgical wire or tiny little screws. When sesamoids fractures are ignored, they can be severely arthritic. If this happens surgical removal may become the only option.
What to do if You Think You Have Sesamoiditis
If you think you have sesamoiditis you have to stop the activity that caused the injury. If you don’t, it won’t get better. Take it seriously. Stop running, cycling, walking uphill and avoid any activity that causes the big toe to bend upward. Ice the ball of the foot 2-3 times per day for 10 minutes. Wear compressive socks to decrease the swelling, even if you don’t think it is swollen. Keep the foot elevated when you are resting. Wear the stiffest shoes you can find. Dansko clogs and super-stiff backpacking boots are the best. Tape the big toe with elastoplast tape to keep the big toe joint still. If it doesn’t go away in a week, seek help from a sports medicine physician who treats these injuries often.
Dr. Christopher Segler is a nationally recognized expert in running biomechanics and running injuries. He lectures around the world to sports medicine podiatrists and foot and ankle surgeons on the topics of barefoot running biomechanics, complicated running injury treatment and reconstructive foot surgery. He has a unique practice in San Francisco where he exclusively caters to runners, triathletes, and elite competitors. He only performs house calls in San Francisco and remote consultations for running injury second opinions and evaluations via Skype and web-conferencing. If you have a quick question about sesamoiditis caused by running you can reach him directly at 415-308-0833. If you live out of state or abroad you can schedule a remote consultation at RunnerSecondOpinions.com. To learn more about house calls for injured runners in San Francisco Bay Area see DocOnTheRun.com.
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