Sesamoiditis is an inflammatory condition of the sesamoid bones which are located on the plantar (bottom) aspect of the first metatarsal phalangeal joint (1st MPJ or big toe joint).  Sesamoiditis occurs at the articulation or joint found between the sesamoid and the overlying 1st metatarsal.  Sesamoiditis is usually caused by chondromalacia, or softening of the surface cartilage of the sesamoid where it articulates with the 1st metatarsal.  As chondromalacia of the sesamoid progresses over time, it will contribute to the onset of osteoarthritis of the articulation of the sesamoid and 1st metatarsal.

A secondary form of sesamoiditis is caused by atrophy of the fat pad of the forefoot.  Thinning of the fat pad beneath the sesamoid can lead to pain with weight bearing by placing direct pressure on the sesamoid.  In this case, there is no chondromalacia found in the sesamoid/1st metatarsal articulation.  Pain under the sesamoid that is caused by thinning of the fat pad may also be called sesamoiditis.

Treatment of Sesamoiditis

Conservative treatment of sesamoiditis consists of limiting activities and padding or 'off loading' of the joint. Off loading refers to taking the weight bearing load off of a particular area by use of a dancer's pad. In the case of sesamoiditis, the pad should be approximately 1/4 thick with a cut out for the bottom of the 1st MPJ. Should padding help, a prescription orthotic with a similar pad would be helpful.  The prognosis of conservative care in cases of sesamoiditis depends upon the stage of chondromalacia found in the sesamoid/1st metatarsal articulation.  In early stages, conservative care of sesamoiditis can be quite successful.  In advanced stages of chondromalacia, off loading will ease pain but will not relieve the sharp shooting arthritic pain of advanced osteoarthritis of the sesamoid/1st metatarsal articulation.

The prognosis of conservative care provided in cases of sesamoiditis caused by fat pad atrophy can be quite good.  A cut out pad like a dancer's pad in conjunction with silicone gel cushioning is very successful.  Although going barefoot may still be uncomfortable, pain can be relieved while wearing shoes.

Surgical treatment of sesamoiditis usually consists of removal of the entire sesamoid bone. Occasionally planing of the bone, or removing the bottom half of the bone may be a useful surgical procedure. Planing is used less often than total excision due to the fact that planing will weaken the sesamoid and may lead to fractures of the sesamoid post-op. As an alternative to sesamoidectomy, a surgically osteotomy can be performed at the base of the first metatarsal to elevate the head of the first metatarsal. This procedure is called a DFWO or dorsiflectory wedge osteotomy. 

A sesamoidectomy can be performed on an out-patient basis at a hospital or surgery center.  The procedure is performed with local anesthesia and mild sedation.  The procedure can be performed in 30 minutes.  Most patients are able to bear weight on the foot the same day of the surgery.  Sutures are removed at two weeks and a return to full weight bearing begins at 4-6 weeks post-op.

A DFWO is a bit more involved that a simple sesamoidectomy.  A DFWO takes about 45 minutes to complete and can be performed under local anesthesia with sedation.  Recovery requires a non-weight bearing hard cast be worn for 6 weeks following surgery.

Removal of the tibial or fibular sesamoids does not typically effect the normal function of the great toe joint. If a patient has a family history of bunions or currently has a bunion, there will be a tendency to increase the rate that a bunion will form with isolated removal of the tibial sesamoid. By removing the tibial sesamoid, the pull of the FHB muscle will become slightly more powerful through the remaining fibular sesamoid. As a result, this may accelerate the formation of a bunion. If there is no history of bunions in the family, this may not even become a factor in choosing to excise the tibial sesamoid.

Sesamoid is derived from Greek and refers to a sesame seed. The Greeks apparently related the shape of the sesamoid bone to a sesame seed.

1st metatarsal phalangeal joint - the big toe joint. Often referred to as the 1st MPJ.

'itis' - used as a suffix and refers to any structure or organ that is inflamed.

plantarflex - to move down toward the plantar surface (or floor), away from the shin.

The two sesamoid bones are located on the bottom surface of the first metatarsal phalangeal joint. The sesamoids are actually a working part of the 1st MPJ and articulate with the plantar surface of the first metatarsal. The sesamoid bones are an extension of the flexor hallucis brevis (FHB) muscle and give the FHB a greater range of motion and improved lever action at the level of the 1st MPJ.

Sesamoid bones are referred to by their location and are called the tibial sesamoid (medial) and the fibular sesamoid (lateral). Tibial and fibular make reference to the bones of the lower leg.

Sesamoid bones are most common to the 1st MPJ but may also be found at other tendon/joint surfaces where a tendon changes direction. Although they're found with much less frequency, other locations include the lesser MPJ's and even the metacarpal phalangeal joint (the thumb).

The flexor hallucis brevis muscle (FHB) originates on the plantar surface of the calcaneus (heel bone). When the FHB fires, its' function is to plantarflex the great toe. The primary function of the FHB is to aid in balance and assist the calf with the toe off portion of gait. As the FHB fires, the load generated by the body of the muscle is sent through the sesamoid to an extension of the FHB tendon that attaches to the plantar aspect of the great toe. The net result is that the great toe plantarflexes using the sesamoid bones to glide around the plantar surface of the 1st MPJ.

A good way to understand the function of the sesamoid bones is to compare the function of the sesamoid to the patella (knee cap).  Accessory bones like the patella or sesamoids are used to facilitate the change in direction applied by a muscle and tendon to a fixed structure.  In the case of the patella, the quadriceps muscle of the thigh uses the patella and the patellar tendon to transfer force to the lower leg.  The end result is that the quadriceps muscle can turn 90 degrees at the knee and still apply tension to the tibia, enabling motion of the lower leg.

Embedded in the body of the FHB tendon, the sesamoids facilitate motion of the great toe.  As we walk, the sesamoids provide a supporting surface to the bottom of the great to and enable the FHB to round the great toe joint with each step that we take.

The onset of sesamoiditis may be insidious or abrupt. An insidious onset would suggest an inflammatory condition of the joint between the articular surface of the sesamoid and the articular surface of the 1st metatarsal. An abrupt onset would suggest a fracture of the sesamoid. Regardless of onset, pain is typical specific to the bottom of the 1st MPJ. Occasionally the entire 1st MPJ may swell and become stiff. Pain is aggravated by long periods of standing, squatting and the use of higher heeled shoes.

X-ray findings in cases of sesamoiditis usually show an increased density of the affected sesamoid bone. When viewing an AP x-ray, the appearance of the bone would light up brighter indicating increased density of the bone consistent with inflammation.

Arthritis

Bunion

Fractured sesamoid

Gout and pseudogout

Hallux limitus and hallux rigidus

Infection of the joint (septic joint)

• Bunion

• Metatarsalgia

• Broken Toe

• Sesamoid Fracture

This article was written by Jeffrey A. Oster, DPM and last updated 1/14/08. No additional references are available for this topic.