Breaking Down Weakness ICD-10 Codes

It’s important to be specific when using weakness ICD-10 codes. Muscle weakness is a complex condition with several potential causes. Sometimes, the cause is evident – a recent injury or a challenging workout — but in other cases, a full work-up and diagnostic tests may be necessary to provide the diagnosis. Symptoms of weakness can result from illness or injury of the brain, nervous system, or muscles.

Conditions and illnesses that can cause weakness include neuromuscular disorders such as multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS) or autoimmune diseases such as Graves’ disease, myasthenia gravis, and Guillain-Barre syndrome. Hyper- and hypothyroidism can both cause weakness. Electrolyte disturbances such as hypokalemia, hypomagnesemia, and hypercalcemia can all cause generalized weakness.

Additionally, many other conditions, such as stroke, polymyositis, alcoholism, and chronic fatigue, can present with their patterns of weakness. Certain medications such as statins, steroids, and certain antiarrhythmic drugs have weakness as a side effect.

ICD-10 for Physical and Occupational Therapists

Physical and occupational therapists must use International Classification of Diseases (ICD-10) codes if they work in a HIPAA-covered entity, regardless of whether they manage a cash practice or receive insurance payments. The coding system expedites information and enables improved communication throughout the medical industry. This uniformity is especially useful when patients are seeing several specialists. Insurance companies use weakness ICD-10 codes to determine the medical necessity of a treatment to receive reimbursement. In addition to the reimbursement angle, these codes track outcomes and assess treatment effectiveness. 

An example illustrates the various portions of that code you will use in your practice.

ICD-10 Code Structure

• Characters 1-3 = The category of the diagnosis
• Characters 4-6 = Etiology, anatomic site, severity, or other clinical detail
• Characters 7 = Extension

EXAMPLE – The following example shows the more detailed information gained through the added characters.

            S52 Fracture of forearm

            S52.5 Fracture of lower end of radius

            S52.52 Torus fracture of lower end of radius

            S52.521 Torus fracture of lower end of right radius

            S52.521A Torus fracture of lower end of right radius, initial encounter

In the above example, S52 is the category.  The fourth and fifth characters of “5” and “2” provide additional clinical detail and anatomic site.  The sixth character (1) indicates laterality, i.e., right radius.  The seventh character, “A,” is an extension that, in this example, means “initial encounter.” The 5th and 6th character sub-classifications represent the most accurate level of specificity.  

ICD-10 Code for Weakness Broken Down

General Weakness Codes

General Weakness (R53.1)

If no determining cause can be found for weakness, this may be used as a primary code. However, it is more often used to code the symptoms of a condition. R53.1 is associated with weakness, diminished energy, lack of concentration and strength.

Muscle Weakness (M62.81)

Code M62.81 can be used when referring to generalized muscle weakness. It can also describe a reduction in muscular strength in multiple sites. There are exclusions to this code:

• Alcoholic myopathy (G72.1)
• Cramp and spasm (R25.2)
• Drug-induced myopathy (G72.0)
• Myalgia (M79.1)
• Stiff-man syndrome (G25.82)

As with all coding, if a more specific code describes the weakness, then use it rather than M62.81 to avoid possible denial of your claim.

Age-Related Weakness Codes

Sarcopenia (M62.84)

Muscle loss starts in the forties for all individuals, but those with sarcopenia experience a more accelerated loss of muscle mass. Symptoms can include muscle weakness, loss of stamina, difficulty performing daily activities, walking slowly, poor balance, and a decrease in muscle size.

Before coding a patient with M62.84, you must first code the underlying disease. Some of the possible underlying diseases include:

• Disorders of the myoneural junction and muscle disease in diseases classified elsewhere (G73.XXX)
• Other and unspecified myopathies (G72.XXX)
• Primary disorders of muscles (G71.XXX)

The exclusions for this code are the same as for M62.81, as seen above.

Asthenia (R54)

Asthenia refers to age-related infirmity and frailty, described as “a state of increased vulnerability to stressors, following declines in function and reserves across multiple physiologic systems, characterized by muscle weakness, fatigue, slowed motor performance; low physical activity; and unintentional weight loss.”

Localized Weakness

In contrast to the above classifications, physical and occupational therapists often see patients with localized areas of weakness.

Contracture of muscle (M62.4)

While muscular contracture may not initially seem like a weakness category, when it is prolonged, it can lead to weakness as in the following conditions:

• Abnormal or permanent shortening of muscle or scar tissue that results in deformity of a joint of the body
• Fibrotic tissue which produces high resistance to the passive stretch of a muscle
• Permanent contraction of a muscle as a result of spasm or paralysis
• Prolonged shortening of the muscle or other soft tissue around a joint prevents joint movement

M62.4 is not a billable code by itself. However, the index contains identifiers that indicate more specificity. For example, M62.461 indicates a contracture in one or more muscles of the right lower extremity.

Facial weakness (R29.810)

This can refer to bilateral facial weakness or right or left facial weakness. This can be used to describe facial droop. Exclusions for this code include:

• Bell’s palsy (G51.0): This condition produces facial muscle paralysis, drooping mouth and other symptoms as a result of damage to the facial nerve.
• Sequelae of cerebrovascular disease (I69): This category includes conditions or residuals resulting from the initial cause. The effects of cerebrovascular disease are numerous. Those covering facial weakness are:
  • Facial weakness following nontraumatic subarachnoid hemorrhage (I69.092)
  • Facial weakness following nontraumatic intracerebral hemorrhage (I69.192)
  • Facial weakness following unspecified cerebrovascular disease (I69.992)
  • Facial weakness following other nontraumatic intracranial hemorrhage (I69.292)
  • Facial weakness following other cerebrovascular disease (I69.892)

Exclusions to M62.81

As mentioned above, the muscular weakness code, M62.81, has several exclusions. This is mostly due to being as specific with your coding as possible, meaning these exceptions tend to be more specific than what the generalized M62.81 code covers. Since some may appear in your clinic, it is worth defining these codes.

• Alcoholic myopathy (G72.1): This condition causes muscles to weaken and lose function due to long-term or heavy alcohol consumption. The acute form typically occurs in malnourished chronic alcoholics following a binge or in the few days of alcohol withdrawal.
• Cramp and spasm (R29.0): This can be used as a primary diagnosis code if no other definitive diagnosis has been established. Exclusions to this code include carpopedal spasm (R29.0), charley horse (M62.831), as well as muscle spasm of the back (M62.830) and muscle spasm of the calf (M62.831)
• Drug-induced myopathy (G72.0): Drug-induced myopathy deserves special mention as it can be produced by several drugs, and presentation may vary with the drug. Common symptoms include proximal muscle weakness, increased muscle enzyme levels (creatine kinase), and electromyographic changes. Drugs known to increase the risk of myopathy include statins, steroids, certain antibiotics, and other agents. 
• Myalgia (M79.10): While this code is listed as an exclusion to M62.81, the two often occur simultaneously. When coding for “myalgia and weakness,” it would typically be coded as M79.1X as the primary code, with R53.1 as a secondary code.
• Stiff-man syndrome (G25.82): Rather than a musculoskeletal condition, this is a nervous system disorder characterized by persistent spasms involving multiple muscles, especially the lower limbs and trunk.

External Cause Codes

As we mentioned earlier, the more specific your code is, the better your chances of receiving prompt reimbursement. Some causes of weakness are related to an initial injury, so external cause codes can be used for these cases. With injury codes, there are often external cause codes that help describe how the initial injury occurred. These codes answer one of the following questions:

• How did the injury occur?
• Where did it happen?
• What was the patient doing when it happened?
• Was it intentional or unintentional?

These only need to be reported for the initial visit. Here’s an example which illustrates how many of these codes can apply to a single individual.

 Some external cause codes (V00-Y99):

• Patient hit by bike while crossing the street — V01: Pedestrian injured in collision with pedal cycle
• Patient experienced a workplace accident — W23: Caught, crushed, jammed, or pinched in or between objects

Place of occurrence codes (Y92):

• Patient was crossing residential street when hit by bicycle — Y92.414: Local residential or business street as the place of occurrence of the external cause
• Patient was involved in a workplace accident on military base — Y92.13: Military base as the place of occurrence of the external cause

These codes are contained in chapter 20 of the ICD-10, titled “External Causes of Morbidity.” While these codes are not mandatory, they add to the specificity of your patient’s injury.

Weakness ICD-10 Coding Best Practices

If ICD-10 codes are new to you, the process may seem overwhelming initially, but following a few simple rules can avoid claim denials and headaches with billing. Be as specific as possible when choosing the codes, and in particular, be diligent in your documentation to support using those codes. An internal audit can double-check your coding abilities, especially if your electronic medical record (EMR) does not have excellent ICD-10 tools. Continue learning ICD-10 processes (and remember, ICD-11 is on the horizon!). We have included some resources below to assist you with this. Finally, remember that consistent and thorough coding will assist your practice and your patient, so staying informed is worth the time.