Webbed toes in humans are a purely cosmetic condition. This condition does not impair the ability to perform any activity, including walking, running, or swimming. Depending on the severity and structure of the webbing, there can be some minor consequences.

People with more severe webbed toes may have a slight disadvantage for activities that benefit from prehensile toes, due to the toes being unable to split or move laterally. Although not scientifically proven, some believe that this condition can possibly allow for a slight advantage, specifically, in athletics. Considering your big toe is a main source for balance, having your second and third toe webbed could virtually be seen as having two big toes. Thus, allowing for better balance in athletics such as running or dance.

Psychological stress may arise from the fear of negative reactions to this condition from people who do not have webbed toes, particularly in severe cases where the nails are stuck visibly close together. Many people with webbed toes can physically feel the toes touching under the fused skin, which can cause psychological discomfort. This is due to the nerves of each toe fully developing and independent muscles working. In other cases where the toes are partially webbed, the webbing holds the separate tips of the toes against one another and prevents the muscles from spreading the toes apart, causing the toes and sometimes nails to press together.

However a disadvantage would be a difficulty in wearing flip-flops or other such footwear in warm countries. People with webbed toes may be unable to wear Toe socks or Vibram FiveFingers shoes. Difficulty navigating rough terrain barefoot, such as rocks at a beach is also common. In some cases the toes grow at different lengths causing the toes to buckle or bend and many people with severe webbed toes experience cramping in these toes due to the muscles and ligaments being strained.

The exact cause of the condition is unknown. In some cases, close family members may share this condition. In other cases, no other related persons have this condition. The scientific name for the condition is syndactyly, although this term covers both webbed fingers and webbed toes. Syndactyly occurs when apoptosis or programmed cell death during gestation is absent or incomplete. Webbed toes occur most commonly in the following circumstances:

- Syndactyly or Familial Syndactyly

- Down syndrome

It is also associated with a number of rare conditions, notably:

- Aarskog–Scott syndrome

- Acrocallosal syndrome

- Apert's syndrome

- Bardet-Biedl syndrome

- Carpenter syndrome

- Cornelia de Lange syndrome

- Edwards syndrome

- Jackson–Weiss syndrome

- Fetal hydantoin syndrome

- Miller syndrome

- Pfeiffer syndrome

- Smith-Lemli-Opitz syndrome

- Timothy syndrome

- Ectodermal Dysplasia

- Klippel-Feil Syndrome

Brachymetatarsia is found to occur more frequently in women than men.

The cause of fibular hemimelia is unclear. Purportedly, there have been some incidents of genetic distribution in a family; however, this does not account for all cases. Maternal viral infections, embryonic trauma, teratogenic environmental exposures or vascular dysgenesis (failure of the embryo to form a satisfactory blood supply) between four and seven weeks gestation are considered possible causes.

In an experimental mouse model, change in the expression of a homeobox gene led to similar, but bilateral, fibular defects.

It remains unconfirmed whether composer Sergei Rachmaninoff's abnormally large reach on a piano was a result of arachnodactyly due to Marfan syndrome, as the pianist exhibited no other signs of the disease.

The reported incidence of constriction ring syndrome varies from 1/1200 and 1/15000 live births. The prevalence is equally in male and female.

Fetomaternal factors like prematurity, maternal illnes, low birth weight and maternal drug exposure are predisposing factors for the constriction ring syndrome.

No positive relationship between CRS and genetic inheritance has been reported.

Hypophalangism is a congenital absence of one or more phalanges (bones of the fingers and toes).

In the above brachydactyly syndromes, short digits are the most prominent of the anomalies, but in many other syndromes (Down syndrome, Rubinstein-Taybi syndrome, etc.), brachydactyly is a minor feature compared to the other anomalies or problems comprising the syndrome.

In racquet nails (also known as brachyonychia, nail en raquette, and racquet thumb), the nail plate is flattened, the end of the thumb is widened and flattened, and the distal phalanx is abnormally short. In racquet nails, the width of the nail bed and nail plate is greater than their length. The condition is painless and asymptomatic.

Racquet nails usually occur on one or both thumbs, but may appear on all fingers and toes. It may be genetic, inherited as an autosomal-dominant trait, or acquired. Genetic disorders associated with racquet nail include Larsen syndrome, Brooke–Spiegler syndrome, Rubinstein–Taybi syndrome, Hajdu–Cheney syndrome, cartilage–hair hypoplasia, pycnodysostosis, acrodysostosis, and brachydactylia.

Acquired racquet nail is associated with acroosteolysis and psoriatic arthropathy. Acquired racquet nail may also be diagnostic of bone resorption in hyperparathyroidism.

Racquet nail often presents with other nail conditions such as onycholysis, koilonychia, pachyonychia, Muehrcke's lines, leuconychia, and half-and-half nails. Cosmetic surgery can be used to improve the appearance of the nails.

This feature can occur on its own, with no underlying health problems. However, it can also be associated with certain medical conditions. Examples include Marfan syndrome, Ehlers-Danlos syndrome, Loeys–Dietz syndrome, congenital contractural arachnodactyly, and homocystinuria.

Arachnodactyly has been linked to mutations in both fibrillin-1 and fibrillin-2 genes.

Brachydactyly (Greek βραχύς = "short" plus δάκτυλος = "finger"), is a medical term which literally means "shortness of the fingers and toes" (digits). The shortness is relative to the length of other long bones and other parts of the body. Brachydactyly is an inherited, usually dominant trait. It most often occurs as an isolated dysmelia, but can also occur with other anomalies as part of many congenital syndromes.

Nomograms for normal values of finger length as a ratio to other body measurements have been published. In clinical genetics the most commonly used index of digit length is the dimensionless ratio of the length of the 3rd (middle) finger to the hand length. Both are expressed in the same units (centimeters, for example) and are measured in an open hand from the fingertip to the principal creases where the finger joins the palm and where the palm joins the wrist.

Five types of syndactyly have been identified in humans. The corresponding loci associated with these types and their common phenotypical expression are as follows:

- "type I": 2q34-q36; webbing occurs between middle and ring fingers and/or second and third toes.

- "type II": 2q31; also involves long and ring fingers, but has a sixth finger merged in between.

- "type III": 6q21-q23; small finger is merged into the ring finger.

- "type IV": 7q36; involves all fingers and/or toes.

- "type V": 2q31-q32; similar to type I, but the metacarpals and metatarsals may also be fused.

The most common problem with syndactyly correction is creeping of the skin towards the fingertip over time. This is likely due to tension at the site of the repair between the digits. Additional surgery may be required to correct this. One critique of using skin grafts is that the grafts darken in the years after surgery and become more noticeable. Also, if the skin grafts are harvested from the groin area, the skin may grow hair. Finally, the fingers may deviate after surgery. This is most commonly seen in complex syndactyly (when there has been a bony joining of the fingers).

Diplopodia is a congenital anomaly in tetrapods that involves duplication of elements of the foot on the hind limb. It comes from the Greek roots diplo = "double" and pod = "foot". Diplopodia is often found in conjunction with other structural abnormalities and can be lethal. It is more extreme than polydactyly, the presence of extra digits.

Supernumerary body parts are most commonly a congenital disorder involving the growth of an additional part of the body and a deviation from the body plan. Body parts may be easily visible or hidden away, such as internal organs.

Many additional body parts form by the same process as conjoined twins: the zygote begins to split but fails to completely separate. This condition may also be a symptom of repeated occurrences of continuous inbreeding in a genetic line.

Morton's Toe is a minority variant of foot shape. Its recorded prevalence varies in different populations, with estimates from 2.95% to 22%.

Congenital causes include: Aarskog syndrome, Albright's hereditary osteodystrophy, and Apert syndrome. Can be caused by a trauma, although the exact mechanism is not known.

Fibular hemimelia or longitudinal fibular deficiency is "the congenital absence of the fibula and it is the most common congenital absence of long bone of the extremities." It is the shortening of the fibula at birth, or the complete lack thereof. In humans, the disorder can be noted by ultrasound in utero to prepare for amputation after birth or complex bone lengthening surgery. The amputation usually takes place at six months with removal of portions of the legs to prepare them for prosthetic use. The other treatments which include repeated corrective osteotomies and leg-lengthening surgery (Ilizarov apparatus) are costly and associated with residual deformity.

Surgical correction is recommended when a constriction ring results in a limb contour deformity, with or without lymphedema.

Sclerodactyly is a localized thickening and tightness of the skin of the fingers or toes. Sclerodactyly often leads to ulceration of the skin of the distal digits and is commonly accompanied by atrophy of the underlying soft tissues.

The term "sclerodactyly" is made up from the Greek "skleros" meaning hard and "daktylos" meaning a finger or toe – "hard fingers or toes".

It is sometimes associated with scleroderma and mixed connective tissue disease, auto-immune disorders.

Sclerodactyly is a component of the CREST variant of scleroderma (CREST is an acronym that stands for calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia.)

Hand-foot-genital syndrome is inherited in an autosomal dominant manner. The proportion of cases caused by de novo mutations is unknown because of the small number of individuals described. If a parent of the proband is affected, the risk to the siblings is 50%. When the parents are clinically unaffected, the risk to the sibs of a proband appears to be low. Each child of an individual with HFGS has a 50% chance of inheriting the mutation. Prenatal testing may be available through laboratories offering custom prenatal testing for families in which the disease-causing mutation has been identified in an affected family member.

Acromesomelic dysplasia is a rare skeletal disorder that causes abnormal bone and cartilage development, leading to shortening of the forearms, lower legs, hands, feet, fingers, and toes. Five different genetic mutations have been implicated in the disorder. Treatment is individualized but is generally aimed at palliating symptoms, for example, treatment of kyphosis and lumbar hyperlordosis.

Specific types of additional body parts include:

- Accessory breast – one or more additional breasts

- Accessory spleen – one or more additional spleens

- Cervical rib – an additional rib

- Diphallia - Having two penes/penises.

- Hermaphroditism – having both sexes' sex organs

- Hyperdontia – additional teeth

- Pelvic digit – a bony growth in the soft tissue of the pelvic region

- Polycephaly – an extra head

- Polydactyly – additional fingers or toes

- Polymelia — an extra arm or leg.

- Polyorchidism – having three or more testicles

- Supernumerary bones – these additional bones are fairly common, particularly in the feet, and are frequently mistaken for fractures on x-rays.

- Supernumerary kidney – a third kidney

- Supernumerary nipples – an additional nipple

- Supernumerary phantom limbs – where the brain acts as though a limb were there, but it is not.

- Syndactyly – webbing between the fingers or toes

- Uterus didelphys – two vaginal canals and/or uteri

There are approximately three hundred known cases of Carpenter Syndrome in the United States. Only 1 in 1 million live births will result in an infant affected by Carpenter Syndrome (RN, 2007).

Carpenter Syndrome is an autosomal recessive disease which means both parents must have the faulty genes in order to pass the disease onto their children. Even if both parents possess the faulty gene there is still only a twenty five percent chance that they will produce a child affected by the syndrome. Their children who do not have the disease will still be carriers and possess the ability to pass the disease onto their offspring if their spouse is also a carrier of the particular gene.

The exact cause is unclear. Proposed factors include wearing overly tight shoes, family history, and rheumatoid arthritis. Some state that footwear only worsens a problem caused by genetics.