Pathogenesis (development of disease)
The metatarsus, consisting of the metatarsal heads, joints, tendons, ligaments as well as connective tissue, acts as a “shock absorber”. It compensates for pressure or compression loads and unevenness of the ground. Due to an incorrect distribution of the load of the metatarsal bones (lat. Ossa metatarsalia I-V (plural/multiple), numbered from medial (“towards the middle”) to lateral (“laterally”), or Os metatarsale (singular/single)) among themselves, the pain occurs. The cause of metatarsalgia (MTG) metatarsal pain) is often a too long 2nd and 3rd metatarsal bone. Furthermore, the fat pad in the area of the sole of the foot decreases due to age. Atrophy (tissue loss) occurs especially under the most heavily loaded heads of the second to fourth metatarsal bones. Other factors that promote metatarsalgia include foot deformities such as hallux valgus (crooked position of the big toe that deviates outward), hammer toe (hallux melleus) and claw toe. In terms of systematics, the following classification of metatarsalgia (MTG) is useful:
- Primary MTG: pain as a result of mechanical reasons (see above).
- Secondary MTG: pain as a result of underlying diseases (eg, rheumatic diseases, Morton’s neuralgia).
Etiology (causes)
Biographical causes
- Genetic burden from parents, grandparents.
- Anatomical variants – too long 2nd and 3rd metatarsals (length difference from 1st metatarsal).
Behavioral causes
- Improper footwear such as high heels (e.g., high heels; heeled shoes > 10 cm) or shoes with poorly cushioned soles.
Disease-related causes
Congenital malformations, deformities and chromosomal abnormalities (Q00-Q99).
- Brachymetatarsia – relatively rare congenital bone growth disorder; usually affects the fourth metatarsal, which stops growing in length earlier than the other bones
- Hollow foot (pes cavus or pes excavatus).
- Bending foot (pes valgus)
- Flatfoot (Pes planus)
- Drop foot
- Pointed toe (Pes equinus)
- Splayfoot (Pes transversoplanus)
Endocrine, nutritional and metabolic diseases (E00-E90).
- Hyperuricemia (elevated uric acid levels in the blood).
Infectious and parasitic diseases (A00-B99).
- Z. E.g. plantar warts (synonyms: verruca plantaris, deep plantar warts).
Musculoskeletal system and connective tissue (M00-M99).
- Arthritis (inflammation of the joints), unspecified.
- Osteoarthritis, unspecified
- Gout (arthritis urica/uric acid-related joint inflammation or tophic gout)/hyperuricemia (elevation of uric acid levels in the blood).
- Hallux malleus (hammer toe)
- Hallux rigidus – arthritic changes stiff big toe metatarsophalangeal joint.
- Hallux valgus (synonyms: bunion; crooked toe).
- Claw toe
- Claw toe
- Köhler’s disease I – rare, (partial) aseptic bone necrosis of the os naviculare pedis (navicular bone); mainly in boys aged 3 to 8 years.
- Rheumatic diseases, unspecified (e.g., rheumatoid arthritis).
- Synovitis (synovial inflammation) of the metatarsophalangeal joint of the small toe.
Neoplasms – tumor diseases (C00-D48).
- Tumors
Psyche – nervous system (F00-F99; G00-G99)
- Morton’s neuralgia (synonyms: Morton’s metatarsalgia, Morton’s syndrome, or Morton’s neuroma) – nerve compression syndrome of the interdigital nerves (nerve branches of the medial plantar nerve and lateral plantar nerve that run between the metatarsals) due to displacement of the nerve-vascular bundle (esp. In the interdigital space D3/4), usually with accompanying bursitis (bursitis); leads to irritation of the nerves of the sole of the foot, which causes seizure-like pain in the area of the metatarsal bones.
Injuries, poisonings and other consequences of external causes (S00-T98).
Laboratory diagnoses – laboratory parameters that are considered independent risk factors.
- Hyperuricemia (elevation of uric acid levels in the blood).
Operations
- Operations on the foot, for example, in the context of surgery for hallux valgus (Keller-Brandes surgery); this shortens the Os metatarsale I (metatarsal bone), which can promote the development of metatarsalgia.
