Rheumatology is a medical specialty that treats diseases affecting joints, muscles, bones, and connective tissues. Rheumatologists see patients with conditions like arthritis, lupus, fibromyalgia, and many other autoimmune and musculoskeletal disorders. Proper medical billing for rheumatology requires understanding the specific ICD-10 codes used to describe these conditions.
ICD-10 codes are the standardized diagnosis codes that healthcare providers use to communicate what conditions patients have. These codes tell insurance companies why patients need treatment and justify the medical services provided. Using the right codes means claims get paid. Using wrong codes leads to denials and lost revenue.
Rheumatology coding can be challenging because many conditions have similar symptoms but different codes. The same disease might have different codes depending on which joints are affected or whether complications are present. Understanding these details helps medical practices bill correctly and get paid appropriately.
This guide explains the most common ICD-10 codes used in rheumatology practices. It covers codes for different types of arthritis, autoimmune diseases, soft tissue disorders, and bone conditions. It also provides billing guidelines to help practices avoid common coding mistakes and maximize proper reimbursement.
Understanding ICD-10 Code Structure for Rheumatology
ICD-10 codes for rheumatology conditions follow specific patterns that help describe diseases accurately. Understanding this structure makes it easier to find the right codes and use them correctly.
Most rheumatology codes start with the letter M, which represents diseases of the musculoskeletal system and connective tissue. The letters and numbers that follow provide more specific information about the condition.
Code Specificity in Rheumatology
Rheumatology codes often require very specific information. Many codes need you to identify:
- Which joints are affected Different codes exist for shoulder arthritis versus knee arthritis versus hand arthritis.
- Which side of the body Codes often specify right side, left side, or both sides (bilateral).
- Whether the condition is with or without complications Rheumatoid arthritis with heart involvement uses different codes than rheumatoid arthritis without organ involvement.
- The specific type of the disease Multiple codes exist for different types of arthritis or lupus.
This specificity means medical coders must read healthcare provider documentation carefully. Vague documentation like “patient has arthritis” does not give enough information to choose the correct code. Good documentation specifies “rheumatoid arthritis of bilateral hands” or “osteoarthritis of right knee.”
Seventh Character Requirements
Many rheumatology codes require a seventh character to provide additional detail. This seventh character might indicate:
- Initial encounter versus subsequent encounter
- Whether a fracture is healing normally or has complications
- The specific location within a joint
Codes with fewer than seven characters need placeholder “X” characters added before the seventh character. For example, a code might be written as M00.061 where the sixth position is used for laterality (right, left, or bilateral).
ICD-10 Code for Rheumatoid Arthritis
Rheumatoid arthritis is one of the most common conditions treated by rheumatologists. It is an autoimmune disease that causes inflammation in joints and can affect other organs. Proper coding for rheumatoid arthritis requires knowing which specific type the patient has and which joints are involved.
Main Rheumatoid Arthritis Codes
The primary code category for rheumatoid arthritis is M05 for seropositive rheumatoid arthritis and M06 for other types of rheumatoid arthritis.
M05 – Rheumatoid arthritis with rheumatoid factor This category covers patients who test positive for rheumatoid factor, a blood test that helps diagnose rheumatoid arthritis.
M06 – Other rheumatoid arthritis This category includes seronegative rheumatoid arthritis (negative rheumatoid factor test) and other variations.
Specific Rheumatoid Arthritis Code Examples
| ICD-10 Code | Description | When to Use |
| M05.40 | Rheumatoid myopathy with rheumatoid arthritis, unspecified site | RA with muscle involvement, location not specified |
| M05.711 | Rheumatoid arthritis with rheumatoid factor of right shoulder without organ or systems involvement | RA affecting right shoulder only |
| M05.712 | Rheumatoid arthritis with rheumatoid factor of left shoulder without organ or systems involvement | RA affecting left shoulder only |
| M05.719 | Rheumatoid arthritis with rheumatoid factor of unspecified shoulder without organ or systems involvement | RA affecting shoulder but side not documented |
| M05.721 | Rheumatoid arthritis with rheumatoid factor of right elbow without organ or systems involvement | RA affecting right elbow only |
| M05.741 | Rheumatoid arthritis with rheumatoid factor of right hand without organ or systems involvement | RA affecting right hand only |
| M05.751 | Rheumatoid arthritis with rheumatoid factor of right hip without organ or systems involvement | RA affecting right hip only |
| M05.761 | Rheumatoid arthritis with rheumatoid factor of right knee without organ or systems involvement | RA affecting right knee only |
| M05.771 | Rheumatoid arthritis with rheumatoid factor of right ankle and foot without organ or systems involvement | RA affecting right ankle/foot only |
| M05.79 | Rheumatoid arthritis with rheumatoid factor of multiple sites without organ or systems involvement | RA affecting many different joints |
Rheumatoid Arthritis with Organ Involvement
When rheumatoid arthritis affects organs beyond the joints, different codes apply. These conditions are more serious and require specific coding.
M05.30 – Rheumatoid heart disease with rheumatoid arthritis Used when RA causes heart problems like pericarditis or valve disease.
M05.20 – Rheumatoid vasculitis with rheumatoid arthritis Used when RA causes inflammation of blood vessels.
M05.10 – Rheumatoid lung disease with rheumatoid arthritis Used when RA affects the lungs, causing inflammation or scarring.
These codes require documentation that the organ involvement is directly related to rheumatoid arthritis, not from a separate condition.
Juvenile Rheumatoid Arthritis
Children with rheumatoid arthritis use different codes than adults. The code category M08 covers juvenile arthritis.
M08.00 – Unspecified juvenile rheumatoid arthritis, unspecified site General code for juvenile RA without more specific information.
M08.40 – Pauciarticular juvenile rheumatoid arthritis, unspecified site Type affecting four or fewer joints.
M08.3 – Juvenile rheumatoid polyarthritis (seronegative) Type affecting five or more joints in children who test negative for rheumatoid factor.
These codes require additional characters to specify which joints are affected and which side of the body.
Osteoarthritis ICD-10 Codes
Osteoarthritis is the most common form of arthritis. It happens when cartilage in joints wears down over time, causing pain and stiffness. Nearly every rheumatology practice treats patients with osteoarthritis.
Primary Osteoarthritis Codes
Primary osteoarthritis develops on its own without a specific injury or other cause. The main code category is M15-M19.
M15 – Polyosteoarthritis Multiple joints affected by osteoarthritis at the same time.
M16 – Osteoarthritis of hip M17 – Osteoarthritis of knee M18 – Osteoarthritis of first carpometacarpal joint (thumb) M19 – Other and unspecified osteoarthritis
Each category breaks down into more specific codes based on whether the condition is primary or secondary, unilateral or bilateral, and which specific joint is involved.
Specific Osteoarthritis Code Examples
| ICD-10 Code | Description | When to Use |
| M15.0 | Primary generalized (osteo)arthritis | OA affecting multiple joint groups throughout body |
| M16.0 | Bilateral primary osteoarthritis of hip | OA in both hips |
| M16.10 | Unilateral primary osteoarthritis, unspecified hip | OA in one hip, but documentation does not say which side |
| M16.11 | Unilateral primary osteoarthritis, right hip | OA in right hip only |
| M16.12 | Unilateral primary osteoarthritis, left hip | OA in left hip only |
| M17.0 | Bilateral primary osteoarthritis of knee | OA in both knees |
| M17.11 | Unilateral primary osteoarthritis, right knee | OA in right knee only |
| M17.12 | Unilateral primary osteoarthritis, left knee | OA in left knee only |
| M18.0 | Bilateral primary osteoarthritis of first carpometacarpal joints | OA in both thumbs |
| M18.11 | Unilateral primary osteoarthritis of first carpometacarpal joint, right hand | OA in right thumb only |
| M19.011 | Primary osteoarthritis, right shoulder | OA in right shoulder |
| M19.012 | Primary osteoarthritis, left shoulder | OA in left shoulder |
| M19.041 | Primary osteoarthritis, right hand | OA in right hand |
| M19.071 | Primary osteoarthritis, right ankle and foot | OA in right ankle/foot |
Secondary Osteoarthritis
Secondary osteoarthritis develops because of another condition or injury. It uses different codes than primary osteoarthritis.
M16.2-M16.7 – Secondary osteoarthritis of hip M17.2-M17.5 – Secondary osteoarthritis of knee
These codes require documentation explaining what caused the secondary osteoarthritis, such as previous injury, infection, or another disease.
Post-Traumatic Osteoarthritis
Osteoarthritis that develops after an injury uses post-traumatic codes.
M16.4 – Post-traumatic osteoarthritis of hip (bilateral) M16.5 – Post-traumatic osteoarthritis of hip (unilateral) M17.2 – Post-traumatic osteoarthritis of knee (bilateral) M17.3 – Post-traumatic osteoarthritis of knee (unilateral)
Documentation should connect the current osteoarthritis to a previous specific injury.
Lupus and Systemic Autoimmune Disease Codes
Systemic lupus erythematosus (SLE) and other autoimmune diseases are common in rheumatology. These conditions affect multiple body systems and require careful coding.
Systemic Lupus Erythematosus Codes
The main code for lupus is M32, with subcategories for different types and complications.
M32.0 – Drug-induced systemic lupus erythematosus Used when lupus is caused by medications. Documentation should identify the specific drug.
M32.10 – Systemic lupus erythematosus, organ or system involvement unspecified
General lupus code when specific organ involvement is not documented.
M32.11 – Endocarditis in systemic lupus erythematosus Lupus affecting the heart lining.
M32.12 – Pericarditis in systemic lupus erythematosus Lupus causing inflammation around the heart.
M32.13 – Lung involvement in systemic lupus erythematosus Lupus affecting the lungs.
M32.14 – Glomerular disease in systemic lupus erythematosus Lupus nephritis affecting kidney filtering units.
M32.15 – Tubulo-interstitial nephropathy in systemic lupus erythematosus Different type of lupus kidney disease.
M32.19 – Other organ or system involvement in systemic lupus erythematosus Lupus affecting organs not covered by other specific codes.
M32.8 – Other forms of systemic lupus erythematosus Unusual lupus variants.
M32.9 – Systemic lupus erythematosus, unspecified Use only when documentation provides no details about type or involvement.
Discoid Lupus
Discoid lupus affects only the skin, not internal organs. It uses code L93.0.
L93.0 – Discoid lupus erythematosus Skin-only lupus with characteristic rash.
This code comes from the skin disease chapter (L codes) instead of the musculoskeletal chapter (M codes) because it primarily affects skin.
Sjögren Syndrome
Sjögren syndrome causes dry eyes and dry mouth due to autoimmune damage to moisture-producing glands.
M35.00 – Sjögren syndrome, unspecified General code when no additional detail is documented.
M35.01 – Sjögren syndrome with keratoconjunctivitis Sjögren with eye inflammation and dryness.
M35.02 – Sjögren syndrome with lung involvement Sjögren affecting the lungs.
M35.03 – Sjögren syndrome with myopathy Sjögren causing muscle weakness.
M35.04 – Sjögren syndrome with tubulo-interstitial nephropathy Sjögren affecting the kidneys.
M35.09 – Sjögren syndrome with other organ involvement Sjögren affecting organs not listed in specific codes.
Other Systemic Autoimmune Diseases
| ICD-10 Code | Description | Condition Details |
| M33.00 | Juvenile dermatomyositis, organ involvement unspecified | Muscle inflammation in children |
| M33.10 | Other dermatomyositis, organ involvement unspecified | Muscle and skin inflammation in adults |
| M33.20 | Polymyositis, organ involvement unspecified | Muscle inflammation without skin involvement |
| M34.0 | Progressive systemic sclerosis | Scleroderma affecting internal organs |
| M34.1 | CR(E)ST syndrome | Limited scleroderma with specific features |
| M34.2 | Systemic sclerosis induced by drug and chemical | Scleroderma caused by medications or toxins |
| M35.1 | Other overlap syndromes | Mixed connective tissue disease |
| M35.3 | Polymyalgia rheumatica | Inflammatory condition causing muscle pain and stiffness |
Gout ICD-10 Codes
Gout is a type of arthritis caused by uric acid crystal deposits in joints. It causes sudden, severe pain and swelling, usually in the big toe but can affect other joints.
Acute Gout Codes
Acute gout is a sudden flare-up with intense pain. The code category M10 covers different types of gout.
M10.00 – Idiopathic gout, unspecified site Gout with no identified cause, location not specified.
M10.011 – Idiopathic gout, right shoulder M10.012 – Idiopathic gout, left shoulder M10.021
– Idiopathic gout, right elbow M10.041 – Idiopathic gout, right hand M10.051 – Idiopathic gout, right hip M10.061 – Idiopathic gout, right knee M10.071 – Idiopathic gout, right ankle and foot
Each joint and side has its own specific code. The most common location is the big toe (first metatarsophalangeal joint).
Drug-Induced Gout
Some medications cause gout by raising uric acid levels. These cases use M10.2 codes.
M10.20 – Drug-induced gout, unspecified site M10.271 – Drug-induced gout, right ankle and foot
Documentation should identify which medication caused the gout.
Chronic Gout
Long-standing gout that persists or recurs frequently uses M1A codes instead of M10 codes.
M1A.00 – Idiopathic chronic gout, unspecified site M1A.011 – Idiopathic chronic gout, right shoulder M1A.071 – Idiopathic chronic gout, right ankle and foot
Chronic gout codes often indicate the presence of tophi (uric acid deposits under the skin).
Gout with Complications
| ICD-10 Code | Description | When to Use |
| M10.30 | Gout due to renal impairment, unspecified site | Gout caused by kidney disease |
| M10.40 | Other secondary gout, unspecified site | Gout caused by other medical conditions |
| M1A.10 | Lead-induced chronic gout, unspecified site | Chronic gout from lead exposure |
| M1A.20 | Drug-induced chronic gout, unspecified site | Chronic gout from medications |
| M1A.30 | Chronic gout due to renal impairment, unspecified site | Long-term gout related to kidney problems |
Fibromyalgia and Soft Tissue Disorder Codes
Fibromyalgia and other soft tissue conditions are frequently seen in rheumatology practices. These disorders affect muscles, tendons, and ligaments rather than joints.
Fibromyalgia
Fibromyalgia causes widespread pain, fatigue, and tender points throughout the body.
M79.7 – Fibromyalgia This is the only code for fibromyalgia. It does not require additional characters or specificity.
Fibromyalgia often occurs alongside other conditions like irritable bowel syndrome, depression, or sleep disorders. These should be coded separately when documented.
Myalgia and Myositis
Muscle pain and inflammation have specific codes.
M79.1 – Myalgia General muscle pain without inflammation.
M60.9 – Myositis, unspecified Muscle inflammation, type not specified.
M60.00 – Infective myositis, unspecified site Muscle infection.
More specific myositis codes exist based on the type of inflammation and which muscles are affected.
Tendinitis and Tenosynovitis
Inflammation of tendons and tendon sheaths is common in rheumatology.
M65.9 – Synovitis and tenosynovitis, unspecified General inflammation of tendon sheath, no specifics documented.
M76.60 – Achilles tendinitis, unspecified leg Inflammation of the Achilles tendon.
M76.61 – Achilles tendinitis, right leg M76.62 – Achilles tendinitis, left leg
M75.30 – Calcific tendinitis of unspecified shoulder Calcium deposits in shoulder tendons causing pain.
M75.31 – Calcific tendinitis of right shoulder M75.32 – Calcific tendinitis of left shoulder
Bursitis
Bursitis is inflammation of the fluid-filled sacs that cushion joints.
M70.60 – Trochanteric bursitis, unspecified hip Inflammation of the bursa on the outer hip.
M70.61 – Trochanteric bursitis, right hip M70.62 – Trochanteric bursitis, left hip
M75.50 – Bursitis of unspecified shoulder M75.51 – Bursitis of right shoulder M75.52 – Bursitis of left shoulder
M70.50 – Other bursitis of knee, unspecified M70.51 – Other bursitis of right knee M70.52 – Other bursitis of left knee
| ICD-10 Code | Description | Common Location |
| M79.7 | Fibromyalgia | Whole body |
| M79.1 | Myalgia | Any muscle |
| M76.61 | Achilles tendinitis, right leg | Back of ankle |
| M75.31 | Calcific tendinitis, right shoulder | Shoulder |
| M70.61 | Trochanteric bursitis, right hip | Outer hip |
| M75.51 | Bursitis of right shoulder | Shoulder |
| M77.9 | Enthesopathy, unspecified | Where tendons attach to bone |
Osteoporosis ICD-10 Codes
Osteoporosis weakens bones, making them fragile and prone to fractures. Rheumatologists often manage osteoporosis treatment.
Osteoporosis Without Current Fracture
M81.0 – Age-related osteoporosis without current pathological fracture Most common type, occurs with aging, no recent fracture.
M81.8 – Other osteoporosis without current pathological fracture Osteoporosis from causes other than aging, no fracture present.
These codes indicate the patient has osteoporosis but has not recently broken a bone due to it.
Osteoporosis With Current Fracture
When a patient with osteoporosis has a fracture from minimal trauma, different codes apply.
M80.0 – Age-related osteoporosis with current pathological fracture Fracture in elderly patient due to weakened bones.
This code requires additional characters to specify fracture location:
M80.00XA – Age-related osteoporosis with current pathological fracture, unspecified site, initial encounter M80.011A – Age-related osteoporosis with current pathological fracture, right shoulder, initial encounter M80.021A – Age-related osteoporosis with current pathological fracture, right humerus, initial encounter M80.051A – Age-related osteoporosis with current pathological fracture, right femur, initial encounter
The seventh character indicates whether this is the first time treating this fracture (A = initial) or a follow-up visit (D = subsequent).
Drug-Induced Osteoporosis
Some medications, especially long-term steroid use, cause osteoporosis.
M81.4 – Drug-induced osteoporosis Used when osteoporosis is caused by medication and no current fracture exists.
M80.4 – Drug-induced osteoporosis with current pathological fracture Used when medication-caused osteoporosis has resulted in a fracture.
Documentation should specify which medication caused the osteoporosis.
Osteopenia
Osteopenia is decreased bone density that is not severe enough to be called osteoporosis.
M85.8 – Other specified disorders of bone density and structure Used for osteopenia since no specific osteopenia code exists.
Some coders use this code for osteopenia, while others use Z codes for screening findings.
Vasculitis ICD-10 Codes
Vasculitis involves inflammation of blood vessels. Various types exist, each with specific codes.
Large Vessel Vasculitis
M31.4 – Aortic arch syndrome (Takayasu) Inflammation of the aorta and its main branches.
M31.5 – Giant cell arteritis with polymyalgia rheumatica Inflammation of large arteries, especially in the head, occurring with muscle pain.
M31.6 – Other giant cell arteritis Large artery inflammation without polymyalgia rheumatica.
Medium and Small Vessel Vasculitis
M30.0 – Polyarteritis nodosa Inflammation of medium-sized arteries throughout the body.
M31.30 – Wegener’s granulomatosis without renal involvement Granulomatosis with polyangiitis affecting lungs and sinuses but not kidneys.
M31.31 – Wegener’s granulomatosis with renal involvement Same condition but also affecting the kidneys.
M31.1 – Thrombotic microangiopathy Small blood vessel disease causing clotting.
M31.0 – Hypersensitivity angiitis Allergic inflammation of small blood vessels.
| ICD-10 Code | Description | Vessels Affected |
| M31.4 | Takayasu arteritis | Large arteries (aorta) |
| M31.5 | Giant cell arteritis with polymyalgia rheumatica | Large arteries (temporal) |
| M31.6 | Other giant cell arteritis | Large arteries |
| M30.0 | Polyarteritis nodosa | Medium arteries |
| M31.30 | Wegener’s granulomatosis without renal involvement | Small vessels |
| M31.0 | Hypersensitivity angiitis | Small vessels |
Ankylosing Spondylitis and Spondyloarthropathies
These conditions cause inflammation in the spine and sometimes other joints.
Ankylosing Spondylitis
Ankylosing spondylitis primarily affects the spine, causing pain and stiffness. In severe cases, vertebrae fuse together.
M45.0 – Ankylosing spondylitis of multiple sites in spine AS affecting several areas of the spine.
M45.1 – Ankylosing spondylitis of occipito-atlanto-axial region AS affecting the upper neck where skull meets spine.
M45.2 – Ankylosing spondylitis of cervical region AS in the neck.
M45.3 – Ankylosing spondylitis of cervicothoracic region AS where neck meets upper back.
M45.4 – Ankylosing spondylitis of thoracic region AS in the upper and middle back.
M45.5 – Ankylosing spondylitis of thoracolumbar region AS where middle back meets lower back.
M45.6 – Ankylosing spondylitis of lumbar region AS in the lower back.
M45.7 – Ankylosing spondylitis of lumbosacral region AS where lower back meets pelvis.
M45.8 – Ankylosing spondylitis of sacral and sacrococcygeal region AS in the very lowest part of the spine.
M45.9 – Ankylosing spondylitis of unspecified sites in spine Use only when documentation does not specify location.
Psoriatic Arthritis
Psoriatic arthritis occurs in some people who have psoriasis, a skin condition.
L40.50 – Arthropathic psoriasis, unspecified General psoriatic arthritis code.
L40.51 – Distal interphalangeal psoriatic arthropathy Psoriatic arthritis affecting finger and toe joints closest to the nails.
L40.52 – Psoriatic arthritis mutilans Severe destructive form of psoriatic arthritis.
L40.53 – Psoriatic spondylitis Psoriatic arthritis affecting the spine.
L40.54 – Psoriatic juvenile arthropathy Psoriatic arthritis in children.
L40.59 – Other psoriatic arthropathy Other types not covered by specific codes.
Note these codes come from the L (skin disease) chapter because psoriatic arthritis is considered a complication of psoriasis.
Reactive Arthritis
Reactive arthritis develops after certain infections, especially gastrointestinal or urinary tract infections.
M02.30 – Reiter’s disease, unspecified site Reactive arthritis with classic triad of arthritis, eye inflammation, and urinary symptoms.
M02.00 – Arthropathy following intestinal bypass, unspecified site Joint disease after bowel surgery.
M02.10 – Postdysenteric arthropathy, unspecified site Arthritis following dysentery infection.
M02.20 – Postimmunization arthropathy, unspecified site Joint inflammation after vaccination.
These codes require additional characters to specify affected joints.
Crystal Arthropathies Beyond Gout
Other types of crystal deposits in joints cause arthritis similar to gout.
Calcium Pyrophosphate Deposition Disease (CPPD)
CPPD, also called pseudogout, occurs when calcium pyrophosphate crystals form in joints.
M11.20 – Other chondrocalcinosis, unspecified site General CPPD code.
M11.00 – Hydroxyapatite deposition disease, unspecified site Different type of calcium crystal deposit.
M11.10 – Familial chondrocalcinosis, unspecified site Inherited form of calcium crystal disease.
Like gout codes, these require additional characters for joint location:
M11.271 – Other chondrocalcinosis, right ankle and foot M11.261 – Other chondrocalcinosis, right knee
Unspecified Crystal Arthropathy
M11.9 – Crystal arthropathy, unspecified Used when crystals are identified but the specific type is unknown.
| ICD-10 Code | Description | Crystal Type |
| M10.00 | Idiopathic gout, unspecified site | Uric acid |
| M11.20 | Other chondrocalcinosis (CPPD), unspecified site | Calcium pyrophosphate |
| M11.00 | Hydroxyapatite deposition disease, unspecified site | Calcium hydroxyapatite |
| M11.9 | Crystal arthropathy, unspecified | Unknown crystal type |
Polymyalgia Rheumatica
Polymyalgia rheumatica causes muscle pain and stiffness, especially in shoulders and hips. It commonly affects people over 50.
M35.3 – Polymyalgia rheumatica This is the primary code for this condition.
Polymyalgia rheumatica often occurs together with giant cell arteritis. When both are present, code both conditions:
- M35.3 (Polymyalgia rheumatica)
- M31.5 or M31.6 (Giant cell arteritis)
The code M31.5 specifically indicates giant cell arteritis with polymyalgia rheumatica and might be used alone when both conditions are clearly documented together.
Raynaud Syndrome and Phenomenon
Raynaud causes fingers and toes to turn white or blue in response to cold or stress due to blood vessel spasms.
I73.00 – Raynaud’s syndrome without gangrene Primary Raynaud phenomenon not associated with other diseases.
M34.0 – Progressive systemic sclerosis When Raynaud occurs as part of scleroderma, code the scleroderma instead.
I73.01 – Raynaud’s syndrome with gangrene Severe Raynaud causing tissue death (very rare).
When Raynaud occurs secondary to other rheumatic diseases like lupus or scleroderma, code the underlying disease rather than Raynaud separately, unless the Raynaud is particularly significant and being separately treated.
Coding for Multiple Joint Involvement
Many rheumatic conditions affect multiple joints simultaneously. Proper coding requires understanding how to handle these situations.
Multiple Sites Codes
When a condition affects several different joint locations (shoulder, knee, and hand, for example), use the “multiple sites” code if available.
M05.79 – Rheumatoid arthritis with rheumatoid factor of multiple sites without organ or systems involvement Use this when RA affects many different joints.
M06.09 – Rheumatoid arthritis without rheumatoid factor, multiple sites Seronegative RA affecting multiple joints.
Bilateral vs Unilateral
When the same joint on both sides of the body is affected (both knees, both hands), some codes have a “bilateral” option while others require separate codes for right and left.
M17.0 – Bilateral primary osteoarthritis of knee Single code for both knees. For joints without bilateral codes, list both right and left:
- M19.011 (Primary osteoarthritis, right shoulder)
- M19.012 (Primary osteoarthritis, left shoulder)
Unspecified Site Codes
Use unspecified site codes only when documentation truly does not indicate location. These should be avoided when possible because they are less specific and might result in lower reimbursement or claim denials.
M06.00 – Rheumatoid arthritis without rheumatoid factor, unspecified site Use only when location is genuinely not documented.
Better documentation that specifies locations allows use of more specific codes that better represent the patient’s condition.
Billing Guidelines for Rheumatology Services
Proper coding is only part of successful rheumatology billing. Following billing guidelines helps practices avoid denials and receive appropriate payment.
Medical Necessity Requirements
Every service billed must be medically necessary. The diagnosis codes must support the procedures and services provided.
For example, billing for rheumatoid arthritis medications requires a rheumatoid arthritis diagnosis code. Billing for osteoporosis bone density testing requires osteoporosis diagnosis codes or risk factor codes.
Insurance companies review medical necessity carefully for expensive medications, infusions, and procedures. Documentation should clearly explain why the service was needed for the specific diagnoses.
Documentation Requirements
Healthcare provider documentation must support the codes used. For specific joint codes, the provider must document which joint is affected and which side (right or left).
“Patient has arthritis” is not sufficient. Good documentation states: “Patient has rheumatoid arthritis affecting bilateral hands, left wrist, and right knee.”
For chronic conditions, documentation should reflect current status. Is the condition stable, improving, or worsening? Are treatments controlling symptoms? This information justifies ongoing care and medication.
Coding to Highest Specificity
Always use the most specific code available that matches the documentation. Using unspecified codes when specific ones exist may result in claim denials or reduced payment.
Instead of M06.9 (Rheumatoid arthritis, unspecified), use M06.09 (Rheumatoid arthritis without rheumatoid factor, multiple sites) when documentation supports it.
The more specific the code, the better it communicates the patient’s actual condition and the complexity of care required.
Common Rheumatology Billing Errors to Avoid
| Error | Why It’s Wrong | How to Fix |
| Using unspecified codes when specifics are documented | Loses reimbursement, may deny | Code to highest specificity documented |
| Forgetting laterality (right/left) | Incomplete code, will reject | Always include right, left, or bilateral |
| Not linking diagnosis to procedure | Medical necessity not shown | Make sure each procedure has supporting diagnosis |
| Coding suspected conditions as confirmed | Violates coding guidelines | Code symptoms until diagnosis is confirmed |
| Using outdated codes | Codes change annually | Update code sets every October |
| Billing for non-covered services without ABN | Patient cannot be billed | Get Advance Beneficiary Notice before service |
Modifier Usage in Rheumatology
Modifiers are two-digit codes added to procedure codes to provide additional information. Common modifiers in rheumatology include:
Modifier 25 Significant, separately identifiable evaluation and management service on the same day as a procedure. Use when a rheumatologist does both an office visit and a joint injection during the same appointment.
Modifier 59 Distinct procedural service. Used to indicate a service is separate from another service performed on the same day.
Modifier RT and LT Right side and left side. Used with some procedure codes to specify which side of the body.
Modifier 76 Repeat procedure by same physician. Used when the same procedure is done twice on the same day.
Proper modifier use prevents claim denials and supports accurate payment.
Pre-Authorization Requirements
Many rheumatology treatments require pre-authorization from insurance companies before services can be provided. This is especially common for:
Biologic medications like adalimumab, etanercept, infliximab, rituximab
Advanced imaging such as MRI scans
High-cost procedures including joint injections with expensive medications
Physical therapy beyond a certain number of visits
Practices should verify authorization requirements before scheduling services. Providing services without required authorization usually results in claim denials that cannot be appealed.
Keep detailed records of authorization approvals including authorization numbers, approval dates, and how many services were authorized.
Special Considerations for Infusion and Injection Billing
Rheumatology practices frequently provide injections and infusions. These services have specific billing requirements.
Joint Injection Coding
Joint injections require both a procedure code (CPT code for the injection) and diagnosis codes explaining why the injection was necessary.
CPT 20610 – Injection of major joint (shoulder, hip, knee) CPT 20605 – Injection of intermediate joint (elbow, wrist, ankle) CPT 20600 – Injection of small joint (fingers, toes)
The diagnosis code should indicate the specific joint being injected. For example, injecting a knee with osteoarthritis uses CPT 20610 with diagnosis code M17.11 (osteoarthritis, right knee) or M17.12 (osteoarthritis, left knee).
When injecting multiple joints during the same visit, bill each injection separately with appropriate modifiers.
Infusion Therapy Coding
Biologic medications given by IV infusion use both administration codes and drug codes.
Administration codes describe the infusion service itself (starting the IV, monitoring the patient). Drug codes describe the specific medication and dosage given.
For example, infliximab infusion uses:
- Administration code for IV infusion
- HCPCS code J1745 for the infliximab drug
- Diagnosis codes for the condition being treated (such as rheumatoid arthritis)
Documentation must include the drug name, dosage, infusion start and stop times, and patient monitoring notes.
Medication Administration Documentation
For infusion and injection billing, documentation should include:
- Specific medication and dose given
- Route of administration (IV, intramuscular, intra-articular)
- Time of administration
- Lot number and expiration date of medication
- Patient’s response to the medication
- Any adverse reactions
Complete documentation supports medical necessity and proves the service was actually provided.
Diagnosis Code Updates and Changes
ICD-10 codes are updated annually every October 1st. Rheumatology practices must stay current with these changes.
Annual Code Updates
Each year, some codes are:
- Added (new codes for newly recognized conditions)
- Deleted (old codes that are no longer valid)
- Revised (existing codes with changed descriptions or requirements)
Using deleted codes after the effective date causes claim rejections. Using old codes when new, more specific codes exist may result in denials.
Practices should update their billing software, encounter forms, and documentation templates annually to reflect current codes.
Staying Current with Code Changes
Review annual update bulletins from CMS and coding organizations
Update billing software to the current code set
Train staff on significant changes affecting commonly used codes Review frequently used codes to verify they are still valid Subscribe to coding newsletters specific to rheumatology
Resources for Rheumatology Coding
Several resources help rheumatology practices stay current:
American College of Rheumatology (ACR) – Provides coding guidelines and resources for rheumatology practices
AAPC and AHIMA – Professional coding organizations offering education and certification
CMS ICD-10 website – Official source for code changes and guidelines Specialty coding books – References specific to rheumatology coding Online coding tools – Searchable databases of current codes
Conclusion: Success in Rheumatology Billing
Proper rheumatology coding requires detailed knowledge of ICD-10 codes, careful attention to documentation, and understanding of billing guidelines. The most commonly used codes include those for rheumatoid arthritis (M05 and M06 series), osteoarthritis (M15-M19), lupus (M32), gout (M10 and M1A), fibromyalgia (M79.7), and various other inflammatory and autoimmune conditions. Each code category includes multiple specific codes based on location, laterality, and presence of complications.
Success in rheumatology billing comes from several key practices. First, healthcare providers must document completely and specifically. Vague notes like “patient has arthritis” do not provide enough information for accurate coding. Detailed documentation that specifies the type of arthritis, which joints are affected, and whether involvement is right-sided, left-sided, or bilateral allows coders to select the most accurate and specific codes available.
Second, coding staff must code to the highest level of specificity supported by documentation. Using unspecified codes when specific codes exist leaves money on the table and may trigger denials. Taking the time to find the exact right code pays off in cleaner claims and faster payment.
Third, practices must make sure medical necessity by linking appropriate diagnosis codes to every service provided. Insurance companies scrutinize rheumatology billing because treatments are often expensive. Clear connections between diagnoses and services help claims pass review on the first submission.
Fourth, staying current with annual code updates prevents using obsolete codes that cause rejections. Investing time each October to review changes, update systems, and train staff saves countless hours of rework later.
Finally, understanding pre-authorization requirements and obtaining approvals before providing services avoids devastating denials for expensive treatments. A few minutes spent verifying coverage and getting authorization prevents losing thousands of dollars on denied claims.
Rheumatology practices that master these coding and billing fundamentals position themselves for financial health. They spend less time on denials and resubmissions and more time on patient care. Their clean claims process quickly, bringing in steady revenue. Their detailed documentation supports medical necessity and protects against audits. Whether billing is handled in-house or outsourced to professional billing companies, the foundation remains the same, accurate codes, complete documentation, and careful attention to payer requirements. These practices benefit everyone:
The practice receives fair payment for services provided, insurance companies process accurate claims efficiently, and patients receive excellent care without unexpected billing problems.
