Assessing and Treating Interosseous Muscle Strains
Did you know you have interosseous muscles in your foot? You know your leg
has various large muscles as the aductors in your upper leg or the tibial muscles
in your lower leg. Well your foot too has very powerful muscles which control the
direction of your toes. As all muscles the interosseous muscles can abduct and
flex, in this case their action is to abduct and flex the toes. Obviously abduction is
less important in the midfoot compared to flexion but let’s first understand the
anatomy of the interosseous musculature in relation to the metatarsal bones of
the foot, as well as the circulatory and nervous systems.
Anatomy of the Interosseous Musculatre of the Foot: Muscles, Tendons
The 4 interossei muscles are situated between the 5 long metatarsal bones of
the midfoot. They are bipenniform muscles, arranged on each side of a tendon.
Each interossei muscle originates by two heads from the proximal half of the
sides of adjacent metatarsal bones. The two heads of the muscle form a central
tendon which passes deep into the metatarsal ligament. The first tendon is
inserted into the medial side of the second toe; the other three are inserted into
the lateral sides of the second, third, and fourth toes.
As mentioned the interosseous muscles’ action is to abduct and flex the toes.
Abduction is less important in the foot compared to flexion at the joints between
the metatarsal bones and the phalanges (toes). These powerful muscles control
the direction of the toes during violent activity, allowing the long and short flexors
to perform their actions.
The interosseous muscles also contribute to maintaining the anterior metatarsal
arch of the foot, as well as to the medial and lateral longitudinal arches of the
foot, due to the position of the joints between the metatarsal bones and the
phalanges (toes). They basically stabilize the foot while walking and running.
The Circulatory and Nervous systems: Nerves and Arteries: The interosseous
muscles are innervated by the lateral plantar nerve. The perforating arteries pass
to the dorsum of the foot between the heads of the three lateral interosseous
muscles. While the deep plantar branch of the dorsalis pedis artery passes
through the space between the heads of the first interossei muscle entering the
sole of the foot.
How and why the Interosseous Musculature Gets Injured
Interosseous Muscle Strains as all strains are muscle and ligament injuries
without dislocation or fracture. They are divided into stable strains and unstable
more severe strains. The interosseous muscle strain is most often a stable strain
caused by overstretching or overexertion of the interosseous musculature. A
strain or tear of one of the small dorsal interosseous muscles may cause sharp
pains, felt between the metatarsal bones of the feet, on the top or beneath the
foot. These precipitate sharp pains may even occur between several metatarsals
simultaneously. In the acute phase of the injury due to these severe pains most
patients will have serious difficulties bearing their full weight on the injured foot.
Additional symptoms are swelling and tenderness painful to touch as well as
bruising on the plantar medial aspect of the foot. All these symptoms cause for a
very limited range of motion of the injured foot. An attempt to perform a
provocative maneuver as one of the medical examinations called the ‘piano key
test’ or a pronation abduction of the foot will elicit unbearable levels of pain.
There are various scenarios causing for this kind of injury or creating this type of
severe pain. The injury may be caused by either direct or indirect loads. Crush
injuries due to a blow to the foot for example are caused by a direct loading
mechanism. This type of injury often results in severe soft tissue damage as well
as compartment syndrome which is a serious condition involving increased
pressure in the muscle compartment which may lead to damage to the
interosseous musculature, damage to the nervous system in the foot and
additional blood circulation problems.
The typical indirect loading mechanism is caused by forced abduction/adduction
or hyperplantarflexion with axial loading. This type of injury often results in
various degrees of soft tissue damage or displacement. Common causes for this
type of injury can occur due to a fall from a great height or even off a curb or
other scenarios causing twisting of the foot; excessive standing or running
activities which may bring on fatigue of the foot; inappropriate footwear as
excessively tight shoes or very high heels; or even walking barefoot on a surface
that requires a shoe for support.
Foot injuries are fairly common among athletes. However fractures of the midfoot
are uncommon due to the constrained arrangement of multiple articular surfaces,
which is improved by capsular attachments and strong ligaments and tendons.
Midfoot injuries usually involve fractures or dislocations of bones together with
soft tissue injuries yet midfoot sprains and other soft tissue injuries can occur on
their own or may continue to cause pain after the fractured bones have healed.
Despite the fact injuries to the midfoot are less common; they have a high risk of
ending an athlete's season or even career.
Interosseus muscle injuries or midfoot sprains as they are often called seem to
be challenging to diagnose since the rate of missed or delayed diagnoses ranges
from 13% to 24%. However timely diagnosis and proper treatment highly
improve the chance of successful healing and reduce the odds for complications.
It’s worth mentioning that certain medical illnesses may contribute to these
missed or delayed diagnoses. For example diabetes patients suffering from
peripheral neuropathy may have a higher threshold for pain and therefore not be
aware of the high level of pain caused by a midfoot sprain.
Interosseus muscle injuries or a midfoot sprain is commonly caused by a Lisfranc
ligament injury. The Lisfranc ligament is a large and strong interosseous ligament
attaching the first cuneiform bone to the second metatarsal bone.
Midfoot sprains can occur at all ages even to children as young as 3 years old
but the they are much more common in athletes participating in many types of
sporting and recreational activities, including football, baseball, basketball,
hockey, soccer, ballet, mountain biking, and windsurfing. Football players in
particular are found to have a high incidence of midfoot sprains (estimated at 4%
per year), often occurring in linemen. The classic mechanism of injury occurs in
football linemen when an axial load is applied to the heel of a fixed plantarflexed
ankle with the toes in dorsiflexion.
Conservative treatment of pain in the acute period consists of rest, compression,
and elevation of the foot to reduce swelling and allow for proper healing. Pain
medication as NSAID’s may also be needed. These types of injuries often take
weeks or months to heal. The recommendation for at least the next 6 weeks
following the acute period is immobilization and non-weight bearing with a cast.
In the case of continued pain after 6 weeks the recommendation is to wear a
controlled ankle motion boot for protected weight bearing together with the use of
crutches for an additional month. Once the pain has subsided a gradual return to
activity is recommended while wearing proper shoes and arch supports.