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Equinus (Tight Calf Muscles)

Updated: Jan 10

In this blog post Cypress foot and ankle specialist Dr. Christopher Correa discusses tight calf muscles (equinus) and how they affect foot function and contribute to foot pain. There is an old saying that goes “if you don’t use it, you lose it” and this rings especially true when talking about flexibility. In the human body flexibility is a function of a few factors including static structure contracture (ligaments and capsules) and muscle tightness. Generally speaking, a joint/muscle unit must be allowed to routinely go through its full range of motion in order to maintain that range of motion. Muscles that are tight or muscle groups that are out of balance can over time lead to a reduction in total available range of motion and subsequent movement compensations. These movement compensations can lead to pain, typically in the form of overuse injuries, by overloading structures or excessive muscle contraction leading to spasm. A couple of examples of conditions commonly seen with equinus are Achilles tendonitis and Posterior Heel Spurs. A tight calf muscle is a more common cause of muscle spasm in young to middle aged people as opposed to a lack of potassium or other electrolyte imbalance. Let's take a closer look at muscle function.

Calf Muscle Function

A 10,000-foot view of muscle movements looks something like this. As muscle contracts it shortens its overall length effecting a force on its associated tendon. The tendon itself by comparison stretches or changes shape very little allowing it to exact force on its boney insertion, moving the bone around a fulcrum known as a joint. Assuming there is no load sufficient to counteract this motion, the bone moves to end range of motion. The joint is made up of two reciprocally shaped bones which are stabilized by static structures known as ligaments. Though ligaments do have some level of elasticity they do not have any muscular attachments and do not affect motion. Rather they stabilize the skeleton while motion occurs guiding the forces and preventing injury. Tightness or contracture tends to occur either at only the muscle or both the muscle and the ligament. A muscle contracture occurs when the muscle no longer can relax to allow for the full range of motion in the direction opposite to its pull. A common example of this in podiatry is the calf muscle known as the gastrocnemius muscle. This muscle is attached to the Achilles tendon and is one of the muscles responsible for you being able to point and stand on your toes. This muscle being stronger than dorsiflexors make it prone to tightening in many people if flexibility is not maintained.

Causes of Equinus

As mentioned before equinus is the medical term for a tight calf muscle. The calf is made up of two muscular heads with one originating from the back of the knee and the other from the lower leg to a single spot behind the heel via the Achilles Tendon. An overly tight calf muscle leads to changes in walking patterns such as shifting of body weight towards the front of the feet, early heel off, increased pronation (flattening) of the arch, and excess strain on the anterior and medial leg tendons. Equinus is usually seen as a component of other diagnoses and is typically implicated in contributing to other conditions such as plantar fasciitis, Achilles tendonitis/ degeneration/ rupture, anterior muscle group tendonitis, bone spur formation, general tired and achy feet, forefoot instability, bunions, hammer toes, shin splints and/or muscle spasms especially at night and more. In most, but not all people, the Gastrocnemius is the only muscle head that is abnormally tight. This is the longer of the 2 muscle heads that make up the calf muscle and is the only one which crosses the knee joint. Due to this, when performing proper calf stretching the knee must be in full extension (straight) otherwise the stretch will be applied to the wrong muscle head (Soleus). In less frequent cases both muscles heads are tight, known as Gastrosoleal equinus, and must need to be stretched independently of one another.

Anatomy of Achilles, gastroc, soleus

There is a saying in podiatry that “equinus is the root of all evil” meaning that it is not often the cause of many foot problems but it usually present and is usually a factor contributing to making it worse.

Another form of tightening is contracture of the joint capsule. In this scenario a joint has been fixed in one position for so long that the joint capsule loses it flexibility and no longer has the ability to passively allow joint motion. This is regardless of whether the muscle could allow for proper range of motion. This tends to occur in limbs that have been held in a fixed position for long periods of time secondary to injury or disease. In the setting of trauma this phenomenon when associated with long periods of immobilization following fracture (12 weeks) is known a “Cast Disease” and was one of the reasons surgeons began to dabble in Open Reduction Internal Fixation (ORIF) of fractures. This was to not only get better anatomic alignment and reduce the risk of arthritis but also to achieve early ROM of the joints and prevent disability secondary to cast disease.

Maintaining flexibility is important to promoting balanced normal movement patterns and preventing injury and pain. If you are experiencing foot or ankle pain, make an appointment with the experts at Select Foot and Ankle Specialists and take the first step toward recovery today.

Equinus, tight calf muscle, man measuring ankle.

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