Equinus is a condition in which the upward bending motion of the ankle is limited. Someone with equinus lacks the flexibility to bring the top of the foot toward the front of the leg. Equinus can occur in one or both feet. When it involves both feet, the limitation of motion is sometimes worse in one foot than in the other.
People with equinus develop ways to “compensate” for their limited ankle motion-and this often leads to other foot, leg, or back problems. The most common methods of compensation are flattening of the arch or picking up the heel early when walking, placing increased pressure on the ball of the foot. Other patients compensate by “toe walking,” while a smaller number take steps by bending abnormally at the hip or knee.
There are several possible causes for the limited range of ankle motion. Often it is due to tightness in the Achilles tendon or calf muscles (the soleus muscle and/or gastrocnemius muscle). In some patients, this tightness is congenital (present at birth) and is sometimes an inherited trait. Other patients acquire the tightness through situations that keep the foot pointing downward for extended periods-such as being in a cast, being on crutches, or frequently wearing high-heeled shoes. In addition, diabetes can affect the fibers of the Achilles tendon and cause tightness.
Sometimes equinus is related to a bone blocking the ankle motion. For example, a fragment of a broken bone following an ankle injury, or bone block, can get in the way and restrict motion. Less often, equinus is caused by spasms in the calf muscle. These spasms may be signs of an underlying neurologic disorder, such as cerebral palsy.
Depending on how a patient compensates for the inability to bend properly at the ankle, a variety of foot conditions can develop, including:
Most patients with equinus are unaware they have this condition when they first visit the doctor. Instead, they come to the doctor seeking relief for foot problems associated with equinus.
To diagnose equinus, the foot and ankle surgeon will evaluate the ankle’s range of motion when the knee is flexed (bent) as well as extended (straightened). This enables the surgeon to identify whether the tendon or muscle is tight and to assess whether bone is interfering with ankle motion. X-rays may also be ordered. In some cases, the foot and ankle surgeon may refer the patient for neurologic evaluation.
Treatment includes strategies aimed at relieving the symptoms and conditions associated with equinus.
The patient plays a vital role in minimizing the risk of developing diabetic peripheral neuropathy and in preventing its possible consequences.