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Chapter 13: Diseases of the musculoskeletal system and connective tissue (M00–M99)

Bones, joints, muscles and connective tissue: arthritis and joint disorders, back and neck pain, osteoporosis, soft-tissue problems such as tendinitis and bursitis, lupus and other connective-tissue diseases.

Chapter 13 spans codes M00–M99 in the FY2027 ICD-10-CM tabular list. This guide explains 65 of its most common codes — select a code for its official description, a plain-English explanation and a note on when the code is used.

ICD-10 Chapter 13: Musculoskeletal & Connective Tissue — illustrative image

Codes in this chapter

CodeOfficial descriptionIn plain words
M05.9Rheumatoid arthritis with rheumatoid factor, unspecifiedRheumatoid arthritis in which the rheumatoid factor blood test is positive; the sites involved are not specified.
M06.9Rheumatoid arthritis, unspecifiedRheumatoid arthritis is a chronic autoimmune condition causing painful, swollen joints and progressive joint damage.
M10.9Gout, unspecifiedGout is a form of arthritis caused by uric acid crystals in a joint, causing sudden severe pain, redness and swelling.
M16.11Unilateral primary osteoarthritis, right hipPrimary osteoarthritis of the right hip: wear-and-repair damage of the hip joint cartilage causing pain and stiffness.
M16.12Unilateral primary osteoarthritis, left hipPrimary osteoarthritis of the left hip: wear-and-repair damage of the hip joint cartilage causing pain and stiffness.
M17.0Bilateral primary osteoarthritis of kneePrimary osteoarthritis of both knees: cartilage wear in the knee joints causing pain, stiffness and reduced mobility.
M17.11Unilateral primary osteoarthritis, right kneePrimary osteoarthritis of the right knee: cartilage wear causing pain and stiffness in the knee.
M17.12Unilateral primary osteoarthritis, left kneePrimary osteoarthritis of the left knee: cartilage wear causing pain and stiffness in the knee.
M19.90Unspecified osteoarthritis, unspecified siteOsteoarthritis is joint damage from cartilage wear causing pain and stiffness; site and type unspecified here.
M20.10Hallux valgus (acquired), unspecified footHallux valgus is a bunion: the big toe angles toward the other toes with a bony lump at its base; foot not specified.
M25.50Pain in unspecified jointPain in a joint, recorded without the joint being specified; a symptom code used while the cause is assessed.
M25.511Pain in right shoulderPain in the right shoulder, a symptom code used while the cause (such as rotator cuff disease) is assessed.
M25.512Pain in left shoulderPain in the left shoulder, a symptom code used while the cause is assessed.
M25.551Pain in right hipPain in the right hip, a symptom code used while the cause is assessed.
M25.552Pain in left hipPain in the left hip, a symptom code used while the cause is assessed.
M25.561Pain in right kneePain in the right knee, a symptom code used while the cause is assessed.
M25.562Pain in left kneePain in the left knee, a symptom code used while the cause is assessed.
M25.571Pain in right ankle and joints of right footPain in the right ankle and the joints of the right foot, recorded as a symptom while the cause is assessed.
M25.572Pain in left ankle and joints of left footPain in the left ankle and the joints of the left foot, recorded as a symptom while the cause is assessed.
M32.9Systemic lupus erythematosus, unspecifiedSystemic lupus erythematosus (SLE) is an autoimmune condition that can affect skin, joints, kidneys, blood and other organs.
M34.9Systemic sclerosis, unspecifiedSystemic sclerosis (scleroderma) is an autoimmune condition causing thickening of skin and scarring of internal organs.
M35.00Sjogren syndrome, unspecifiedSjögren syndrome (sicca syndrome) is an autoimmune condition mainly causing dry eyes and dry mouth; type unspecified here.
M35.3Polymyalgia rheumaticaPolymyalgia rheumatica is an inflammatory condition of older adults causing aching and stiffness in the shoulders and hips.
M41.9Scoliosis, unspecifiedScoliosis is a sideways curvature of the spine, most often appearing in adolescence; type not specified here.
M43.16Spondylolisthesis, lumbar regionSpondylolisthesis is slippage of one vertebra forward over the one below it, here in the lumbar (lower back) region.
M47.812Spondylosis without myelopathy or radiculopathy, cervical regionCervical spondylosis is age-related wear of the neck (cervical) spine joints and discs, here without nerve or cord compression.
M47.816Spondylosis without myelopathy or radiculopathy, lumbar regionLumbar spondylosis is age-related wear of the lower back joints and discs, here without nerve or cord compression.
M48.02Spinal stenosis, cervical regionSpinal stenosis in the neck: narrowing of the spinal canal in the cervical region that can press on the spinal cord.
M48.061Spinal stenosis, lumbar region without neurogenic claudicationLumbar spinal stenosis is narrowing of the spinal canal in the lower back, here without leg pain from nerve compression when walking.
M48.062Spinal stenosis, lumbar region with neurogenic claudicationLumbar spinal stenosis with neurogenic claudication: canal narrowing in the lower back causing leg pain and heaviness when walking.
M50.30Other cervical disc degeneration, unspecified cervical regionCervical disc degeneration is wear and drying of the discs in the neck, a common cause of neck pain and stiffness.
M51.16Intervertebral disc disorders with radiculopathy, lumbar regionA lumbar disc disorder with radiculopathy: a lower-back disc problem that presses on a nerve root, causing leg pain (sciatica).
M51.26Other intervertebral disc displacement, lumbar regionDisplacement (herniation or bulge) of a disc in the lumbar spine, which may press on nearby nerves.
M54.12Radiculopathy, cervical regionCervical radiculopathy is pain, numbness or weakness in the arm from a pinched nerve root in the neck.
M54.16Radiculopathy, lumbar regionLumbar radiculopathy is pain, numbness or weakness down the leg from a pinched nerve root in the lower back (sciatica-type pain).
M54.2CervicalgiaCervicalgia is pain in the neck, recorded as a symptom while the cause is assessed.
M54.31Sciatica, right sideSciatica on the right side: pain radiating from the lower back down the back of the right leg, along the sciatic nerve.
M54.32Sciatica, left sideSciatica on the left side: pain radiating from the lower back down the back of the left leg.
M54.41Lumbago with sciatica, right sideLow back pain (lumbago) radiating down the right leg in a sciatica pattern.
M54.42Lumbago with sciatica, left sideLow back pain (lumbago) radiating down the left leg in a sciatica pattern.
M54.50Low back pain, unspecifiedLow back pain (lumbago) recorded without a specified cause or radiation pattern.
M54.9Dorsalgia, unspecifiedDorsalgia means pain in the back; here the region and cause are not specified.
M62.81Muscle weakness (generalized)Generalised muscle weakness is reduced strength in muscles throughout the body, recorded as a finding while the cause is assessed.
M62.838Other muscle spasmMuscle spasm in a site other than the neck and back: a sudden, involuntary tightening of a muscle.
M65.30Trigger finger, unspecified fingerTrigger finger is catching or locking of a finger as it bends, from a thickened tendon sheath; finger not specified.
M67.40Ganglion, unspecified siteA ganglion is a benign fluid-filled swelling arising from a joint or tendon sheath, often at the wrist; site not specified.
M72.0Palmar fascial fibromatosis [Dupuytren]Dupuytren contracture is thickening and shortening of the tissue under the palm skin, gradually bending the fingers.
M75.101Unspecified rotator cuff tear or rupture of right shoulder, not specified as traumaticA tear or rupture of the rotator cuff of the right shoulder not attributed to a specific injury, with completeness unspecified.
M75.102Unspecified rotator cuff tear or rupture of left shoulder, not specified as traumaticA tear or rupture of the rotator cuff of the left shoulder not attributed to a specific injury, with completeness unspecified.
M75.41Impingement syndrome of right shoulderImpingement syndrome of the right shoulder: the rotator cuff tendons are pinched under the shoulder blade's bony arch, causing pain on lifting.
M75.42Impingement syndrome of left shoulderImpingement syndrome of the left shoulder: pinching of the rotator cuff tendons causing pain on lifting the arm.
M76.61Achilles tendinitis, right legAchilles tendinitis is inflammation or degeneration of the right Achilles tendon, causing pain at the back of the heel.
M76.62Achilles tendinitis, left legAchilles tendinitis is inflammation or degeneration of the left Achilles tendon, causing pain at the back of the heel.
M77.11Lateral epicondylitis, right elbowLateral epicondylitis ('tennis elbow') of the right elbow: pain where the forearm extensor tendons attach to the outer elbow.
M77.12Lateral epicondylitis, left elbowLateral epicondylitis ('tennis elbow') of the left elbow: pain at the outer elbow from the forearm tendon attachment.
M79.10Myalgia, unspecified siteMyalgia means muscle pain; the site is not specified here.
M79.2Neuralgia and neuritis, unspecifiedNeuralgia and neuritis are pain and inflammation along a nerve, recorded here without a specified nerve or cause.
M79.641Pain in right handPain in the right hand, recorded as a symptom while the cause is assessed.
M79.642Pain in left handPain in the left hand, recorded as a symptom while the cause is assessed.
M79.671Pain in right footPain in the right foot, recorded as a symptom while the cause is assessed.
M79.672Pain in left footPain in the left foot, recorded as a symptom while the cause is assessed.
M79.7FibromyalgiaFibromyalgia is a long-term condition of widespread pain, fatigue, unrefreshing sleep and cognitive fog.
M81.0Age-related osteoporosis without current pathological fractureAge-related osteoporosis is thinning of the bones with ageing that raises fracture risk, here without a current fracture.
M85.80Other specified disorders of bone density and structure, unspecified siteOther specified disorders of bone density and structure (such as osteopenia, low bone density below the osteoporosis range); site unspecified.
M86.9Osteomyelitis, unspecifiedOsteomyelitis is infection of a bone, causing pain, fever and swelling; site and course not specified here.

This guide explains ICD-10-CM codes in plain language for patients, students and other readers. It is educational information only — not coding, billing or medical advice. The code recorded for any real encounter is assigned from the full clinical documentation by the treating team and qualified coders, and only they can decide which code fits a specific case.

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