416 articles
Lateral dislocation of patella
Lateral dislocation of patella, also called lateral patellar dislocation, is a knee injury where the kneecap displaces outward, typically without contact, in young and active people.
Le Fort fracture of skull
Le Fort fracture of skull: bilateral midface fracture separating facial skeleton from cranial base; types I (horizontal), II (pyramidal), III (craniofacial dissociation); pterygoid plate fracture unifies all; from René Le Fort's 1901 cadaver experiments.
Legg–Calvé–Perthes disease
Legg–Calvé–Perthes disease (LCPD, Perthes disease) is idiopathic avascular necrosis of the femoral head in children aged about 4–8, male-to-female 4:1, described by Legg, Calvé, and Perthes around 1910, healing over 2–4 years.
Lenz-Majewski hyperostotic dysplasia
Lenz-Majewski hyperostotic dysplasia (Lenz-Majewski syndrome, LMHD) is an ultra-rare autosomal dominant bone dysplasia caused by gain-of-function PTDSS1 variants, with craniotubular hyperostosis, cutis laxa, intellectual disability, and about 23 reported cases.
Leri pleonosteosis
Leri pleonosteosis, also known as Léri's pleonosteosis, is a very rare autosomal dominant skeletal condition causing joint contractures, short stature, and spade-shaped broad thumbs and great toes.
Limb-mammary syndrome
Limb-mammary syndrome (LMS, ORPHA 69085, OMIM 603543) is a rare autosomal dominant TP63-related ectodermal dysplasia with split-hand/foot anomalies, breast and nipple hypoplasia, and tooth and nail defects; distinct from TBX3-related ulnar-mammary syndrome.
Lisfranc injury
Lisfranc injury: fracture and/or dislocation of the midfoot disrupting tarsometatarsal joints, also called tarsometatarsal injury. About 0.2% of fractures, over 20% missed initially; treated nonoperatively, by ORIF, or by primary arthrodesis (fusion).
Loose body in joint
Loose body in joint (joint mouse, intra-articular loose body, ICD-10 M24.0, ICD-11 FA34.0): a free fragment of cartilage or bone in a joint, caused by osteochondritis dissecans, synovial chondromatosis, osteophytes, fractures, or meniscal damage; treated by arthroscopic removal.
Loose body in knee
Loose body in knee (ICD-11 FA33.3): a free-floating cartilage or bone fragment in the knee joint causing catching, locking, and pain. Causes include osteochondritis dissecans, osteoarthritis, trauma, and synovial chondromatosis; treated by arthroscopic removal plus management of the underlying disease.
Low bone mass disorders
Low bone mass disorders (ICD-11 FB83) group osteopenia, osteoporosis, and adult osteomalacia: conditions of reduced bone mineral density, fragile bone, or defective mineralization, assessed by DXA T-scores and FRAX and treated mainly with bisphosphonates.
Macrodactyly of toes
Macrodactyly of toes, also called macrodactyly of the foot, is a rare congenital condition present from birth in which one or more toes are enlarged.
Maffucci syndrome
Maffucci syndrome, also called enchondromatosis with hemangiomata or Kast syndrome, is a rare non-hereditary disorder of multiple enchondromas plus hemangiomas, caused by somatic mosaic IDH1/IDH2 mutations, with high chondrosarcoma risk.
Majeed syndrome
Majeed syndrome (MJDS, OMIM 609628), also called LPIN2-related CRMO, a rare autosomal recessive autoinflammatory disease with early-onset chronic recurrent multifocal osteomyelitis, congenital dyserythropoietic anemia, and sometimes Sweet syndrome, treated with anti-IL-1 agents.
Mandibuloacral dysplasia
Mandibuloacral dysplasia (MAD, MADA/MADB) is an ultrarare autosomal recessive progeroid laminopathy with mandibular and clavicular hypoplasia, acro-osteolysis, skin pigmentation changes, and lipodystrophy, caused by LMNA (type A) or ZMPSTE24 (type B) mutations.
Mazabraud syndrome
Mazabraud syndrome, also called myxoma with fibrous dysplasia, is a rare GNAS-related disorder combining fibrous dysplasia of bone with intramuscular myxomas, usually polyostotic, adult-onset, prevalence under 1 in 1,000,000.
Melnick-Needles syndrome
Melnick-Needles syndrome (MNS, osteodysplasty, OMIM 309350) is a rare X-linked dominant skeletal dysplasia from FLNA gain-of-function variants, mainly exon 22; severe in males, lethal perinatally, under 100 reported cases.
Melorheostosis
Melorheostosis (Leri's disease, candle wax disease): rare sclerosing bone dysplasia, usually one limb, with flowing hyperostosis on x-ray; caused by somatic MAP2K1 mutations in about half of cases; not inherited.
Melorheostosis with osteopoikilosis
Melorheostosis with osteopoikilosis (mixed sclerosing bone dysplasia, ORPHA:1879, OMIM 166700) is an ultra-rare autosomal dominant bone dysplasia combining dripping candle wax hyperostosis with osteopoikilosis, linked to LEMD3 and somatic MAP2K1 mutations.
Mesoaxial synostotic syndactyly with phalangeal reduction
Mesoaxial synostotic syndactyly with phalangeal reduction (MSSD, syndactyly type 9, Malik-Percin type, OMIM 609432) is an extremely rare autosomal recessive limb malformation with fused 3rd-4th fingers, metacarpal synostosis, and BHLHA9 mutations.
Mesomelia-synostoses syndrome
Mesomelia-synostoses syndrome (Verloes-David-Pfeiffer syndrome, 8q13 microdeletion syndrome) is a rare autosomal dominant skeletal dysplasia with mesomelic limb shortening, acral synostoses, facial features, and palatal anomalies, caused by SULF1/SLCO5A1 deletions.
Mesomelic dysplasia, Kantaputra type
Mesomelic dysplasia, Kantaputra type (MDK, Thai type) is a rare autosomal dominant skeletal dysplasia with mesomelic limb shortening, fibulo-calcaneal synostosis, and HOXD-cluster duplications at 2q31.1-q31.2.
Mesomelic dysplasia, Nievergelt type
Mesomelic dysplasia, Nievergelt type (Nievergelt syndrome, ORPHA:2633) is an extremely rare bone dysplasia with severe mesomelic limb shortening, triangular or rhomboid tibiae and fibulae, synostoses, and skin dimples; onset antenatal or neonatal.
Mesomelic dysplasia, Savarirayan type
Mesomelic dysplasia, Savarirayan type (triangular tibia-fibular aplasia syndrome, OMIM 605274) is a rare skeletal dysplasia with hypoplastic triangular tibiae and absent fibulae, caused by de novo 6p22.3 microdeletions affecting ID4 regulation.
Metabolic bone disease of prematurity
Neonatal osteopenia, also called osteopenia of prematurity or metabolic bone disease of prematurity, is reduced bone mineralization in preterm infants after interrupted third-trimester calcium and phosphorus accretion, affecting up to 30-32% of very low birth weight infants.
Metachondromatosis
Metachondromatosis (MC, OMIM 156250) is a rare autosomal dominant skeletal disorder with both enchondromas and osteochondromas in the hands, feet, and long bones, caused by loss-of-function PTPN11 mutations; lesions point toward the epiphysis, regress spontaneously, and rarely turn malignant.
Metaphyseal anadysplasia
Metaphyseal anadysplasia (MAD, MIM 602111/613073) is a rare regressive skeletal dysplasia from MMP13 or MMP9 variants: infantile metaphyseal irregularity, leg bowing, and short stature that spontaneously resolve in childhood.
Metaphyseal chondrodysplasia, Schmid type
Metaphyseal chondrodysplasia, Schmid type (SMCD, MCDS, OMIM 156500) is a rare autosomal dominant COL10A1 skeletal dysplasia causing short-limbed short stature, bowed legs, coxa vara, and waddling gait, distinguished from rickets by normal labs.
Metatropic dysplasia
Metatropic dysplasia (metatropic dwarfism), a rare autosomal dominant TRPV4-related spondyloepimetaphyseal dysplasia: short limbs and long trunk at birth, progressive kyphoscoliosis reversing proportions, dumbbell long bones, halberd pelvis, adult height 107-135 cm.
Metopic ridge
Metopic ridge: a benign midline forehead ridge from normal thickening after the metopic suture fuses at 3-9 months; distinguished from metopic craniosynostosis (trigonocephaly), which is surgical.
Minodronic acid
Minodronic acid (minodronate, YM-529; Recalbon/Bonoteo) is a third-generation nitrogen-containing bisphosphonate for osteoporosis, developed in Japan, approved January 2009, dosed 1 mg daily or 50 mg every 4 weeks, use limited to Japan.