Knee ICD-10 codes

Unilateral primary osteoarthritis affecting one knee where the specific side (right or left) has not been documented or identified by the treating provider.

M17.11 identifies idiopathic (primary) osteoarthritis affecting the right knee only, with no contralateral involvement and no traumatic or secondary cause documented.

M17.12 identifies degenerative joint disease confined to the left knee that arises idiopathically — not from prior injury, inflammatory arthritis, or another underlying condition.

Post-traumatic osteoarthritis affecting one knee, with the specific side (right or left) not documented or not specified by the treating provider.

Post-traumatic osteoarthritis of the right knee arising as a sequela of prior joint injury, coded as a unilateral condition with confirmed right-side laterality.

Post-traumatic osteoarthritis of the left knee arising as a direct sequela of documented prior joint trauma, affecting one knee only.

Chronic, non-traumatic condition in which the patella repeatedly displaces from the trochlear groove, coded here when the treating clinician has not specified whether the right or left knee is affected.

Recurrent dislocation of the patella at the right knee — a non-traumatic, pattern-based diagnosis indicating the kneecap has dislocated multiple times, reflecting underlying patellar instability rather than a single acute event.

M22.02 identifies recurrent dislocation of the patella in the left knee — a chronic instability pattern in which the kneecap repeatedly displaces from the trochlear groove, distinct from a single traumatic event.

Recurrent subluxation of the patella with laterality not documented or specified in the clinical record.

Chronic, repetitive incomplete dislocation of the right patella in which the kneecap repeatedly slides partially out of the trochlear groove without fully dislocating.

Recurrent subluxation of the left patella — repeated episodes of incomplete kneecap displacement from the trochlear groove, left side only, not caused by a single acute traumatic event.

Softening or breakdown of the cartilage on the underside of the kneecap, coded without specification of which knee is affected.

Softening and surface breakdown of the cartilage on the posterior face of the right patella, classified under disorders of the patella in the musculoskeletal chapter.

Degenerative softening and breakdown of the articular cartilage on the underside of the left kneecap (patella), classified under patellar disorders in ICD-10-CM Chapter 13.

M22.90 classifies a patellar disorder that cannot be assigned to a more specific subcategory and for which laterality (right vs. left) is also undocumented.

M22.91 captures an unspecified disorder of the patella localized to the right knee — used when a specific patellar condition cannot be identified or documented with greater precision.

M22.92 identifies an unspecified disorder of the patella (kneecap) localized to the left knee, used when a specific patellar condition cannot be further classified.

M23.40 identifies a loose body within the knee joint when the operative or affected side is not documented or cannot be determined.

M23.41 identifies an intra-articular loose body — a free fragment of bone, cartilage, or both — specifically within the right knee joint.

M23.42 identifies a loose body — a detached fragment of bone, cartilage, or other intra-articular material — present within the left knee joint.

Chronic instability of the knee, reported when laterality (right or left) is not documented in the medical record.

Chronic instability of the right knee due to ligamentous insufficiency, representing a persistent, non-acute condition of the right knee joint that has not resolved after the initial injury period.

Chronic instability of the left knee due to ligamentous laxity or insufficiency, representing a persistent, non-acute condition affecting joint integrity on the left side.

M23.90 classifies internal derangement of the knee when neither the specific type of derangement nor the laterality (right or left) is documented in the medical record.

M23.91 identifies an internal derangement of the right knee where the specific structure involved — meniscus, ligament, loose body, or other intra-articular component — has not been further defined in the clinical documentation.

M23.92 classifies unspecified internal derangement of the left knee — used when the clinical picture points to a structural knee joint problem on the left side but the specific pathology (meniscal tear, ligament laxity, loose body, etc.) cannot be identified from the documentation.

M67.50 identifies plica syndrome affecting the knee when the operative or clinical record does not specify right or left laterality.

M67.51 classifies plica syndrome specifically affecting the right knee — an irritation or thickening of the synovial plica fold within the right knee joint, categorized under other disorders of synovium and tendon.

M67.52 identifies plica syndrome specifically affecting the left knee — irritation or inflammation of a synovial membrane fold within the left knee joint, classified under other disorders of synovium and tendon.

Inflammation of the prepatellar bursa — the fluid-filled sac anterior to the kneecap — classified here when the affected side (right or left) is not documented in the medical record.

Prepatellar bursitis of the right knee — inflammation of the bursa sac situated directly anterior to the patella, attributed to use, overuse, or sustained pressure on the joint.

Inflammation of the prepatellar bursa — the small fluid-filled sac directly anterior to the patella — specifically affecting the left knee, classified under soft tissue disorders related to use, overuse, and pressure.

M70.50 classifies bursitis of the knee — specifically bursal inflammation not attributable to the prepatellar bursa (M70.4x) — when laterality is undocumented or unspecified.

M70.51 identifies bursitis of the right knee involving a bursa other than the prepatellar bursa, typically arising from occupational use, overuse, or repetitive pressure on the joint.

Inflammation of a bursa at the left knee, classified under soft tissue disorders linked to use, overuse, or pressure — excluding prepatellar bursitis, which has its own code (M70.42).

A fluid-filled synovial cyst arising in the popliteal fossa (Baker's cyst) where the affected knee is not specified as right or left in the documentation.

Baker's cyst (synovial cyst of the popliteal space) specifically involving the right knee — a fluid-filled sac arising from the semimembranous bursa or the knee joint capsule, located in the posterior popliteal fossa.

M71.22 identifies a Baker's cyst (synovial cyst of the popliteal space) specifically located at the left knee — a fluid-filled sac that forms behind the left knee joint when excess synovial fluid accumulates in the popliteal fossa.

Iliotibial band syndrome affecting an unspecified leg — use only when the treating provider has not documented which leg is involved.

Iliotibial band syndrome affecting the right leg, classified under lower limb enthesopathies, characterized by friction-related inflammation where the IT band crosses the lateral femoral epicondyle.

Iliotibial band syndrome of the left leg — a friction-based enthesopathy of the lower limb where the IT band repeatedly rubs against the lateral femoral epicondyle, producing lateral knee or thigh pain.

Tibial collateral bursitis (Pellegrini-Stieda syndrome) of an unspecified leg — inflammation of the bursa adjacent to the tibial collateral ligament at the medial knee, without documented laterality.

Inflammation or calcification of the bursa adjacent to the tibial collateral (medial collateral) ligament at the right knee, consistent with Pellegrini-Stieda syndrome.

Inflammation of the bursa at the tibial collateral ligament on the left knee, classified under Pellegrini-Stieda syndrome — a condition involving calcification or bursitis at the medial femoral condyle insertion of the tibial collateral ligament.

M76.50 classifies patellar tendinitis — inflammation of the tendon connecting the kneecap to the tibia, commonly called jumper's knee — when the treating clinician has not documented which knee is affected.

Patellar tendinitis of the right knee — an enthesopathy involving inflammation of the patellar tendon at or near its attachment to the inferior pole of the patella, classified under lower limb enthesopathies (M76).

Patellar tendinitis of the left knee — an enthesopathy involving inflammation of the patellar tendon at or near its origin on the inferior pole of the left patella.

Osteochondrosis affecting the patella in a skeletally immature patient, coded when the treating clinician has not specified or documented which knee is involved.

M92.41 identifies juvenile osteochondrosis affecting the patella of the right knee — a developmental chondropathy of the kneecap's ossification center occurring in skeletally immature patients.

M92.42 identifies juvenile osteochondrosis of the patella specifically at the left knee — covering both the primary patellar center (Köhler) and secondary patellar center (Sinding-Larsen) variants in a skeletally immature patient.

Degenerative joint disease affecting both the right and left knee simultaneously, arising without a known precipitating cause, injury, or underlying condition — distinguishing it from post-traumatic or secondary osteoarthritis.

Bilateral post-traumatic osteoarthritis of the knee, where degenerative joint disease affecting both knees is attributable to a prior traumatic event rather than primary age-related degeneration.

M17.4 captures bilateral knee osteoarthritis that is secondary in origin — meaning it developed as a consequence of an identifiable underlying cause other than trauma, such as rheumatoid arthritis, gout, septic arthritis, metabolic disease, or congenital deformity — and affects both knees simultaneously.

M17.5 captures osteoarthritis of a single knee that developed secondary to an underlying condition — such as prior inflammatory arthritis, obesity, crystal deposition disease, or metabolic disorder — where the etiology is not post-traumatic and does not fit a more specific secondary OA code.

Degenerative, noninflammatory disease of the knee joint without specification of laterality or etiology — used only when the clinical record does not support a more granular M17 code.

M66.0 classifies spontaneous rupture of a popliteal (Baker's) cyst — the dissection or decompression of a synovial fluid-filled cyst in the posterior knee space that occurs when normal force is applied to already-weakened tissue.

Enlargement or hypertrophy of the infrapatellar (Hoffa's) fat pad, a soft tissue structure anterior to the knee joint and posterior to the patellar tendon, classified under other soft tissue disorders.