The hands are often considered to be of major cosmetic importance, to some degree like the face. It is constant contact with the environment and can be at risk of a host of cosmetic problems. Thickening of the skin on the hands may be due to various causes, such as calluses. A lesser known condition affecting the skin of the hands is known as knuckle pads which may present in a similar fashion to calluses, and is more common than often thought.
What are knuckle pads?
Knuckle pads are skin lesions over the finger joints on the back surface of the hand. These lesions are pimples (papules), lumps (nodules) or patches (plaques) and are benign (non-cancerous). Knuckle pads are also asymptomatic meaning that there is no pain, itching or other symptoms present. It usually forms with repeated trauma to the area, which may be occupational or occur with playing certain sports.
Overall knuckle pads are not considered to be a serious condition and many people do not seek medical treatment for it. Therefore the prevalence is difficult to estimate but the condition is known to be fairly common. It is usually considered to be more of a cosmetic problem. Knuckle pads affect men and women equally and can occur at any age but is more commonly seen in people over the age of 40 years.
Causes of Knuckle Pads
The exact reason why knuckle pads arises is unclear because some cases are unrelated to repeated irritation. In fact a large number of cases are due to idiopathic factors (unknown causes). Repetitive trauma is another common cause. The repeated pressure and friction are the causative factors. This irritation may not always be physical. Sometimes repeated chemical exposure could also be responsible.
Genetic factors also seem to play a role. There is usually a family history of knuckle pads and it tends to start around the same age within a family. This age of onset varies from one family to another but typically arises after 30 years of age and usually after 40. Even in these cases where genetics appear to be a factor, a history of repetitive trauma could serve as a trigger in those affected.
Knuckle pads have also been seen to occur in conjunction with certain diseases including:
- Dupuytren disease
- Peyronie disease
- Ledderhose disease
- Esophageal cancer
- Oral leukoplakia
- Clubbed fingers
The exact mechanism behind the development of knuckle pads in some of these conditions is not always clear. Repetitive trauma may not always be present, as is the case with idiopathic and genetic causes.
Signs and Symptoms
Knuckle pads appear as papules, nodules of plaques on the skin over the finger joints. There are usually no other symptoms as would be expected of skin lesions, such as itching, although pain and tenderness are sometimes reported.
It tends to appear over the metacarpophalangeal (MCP) joints (the area between the hand bones and finger bones) as well as over the proximal interphalangeal (PIP) joints (between the first and second finger bones). Knuckle pads can appear over any bony prominence on the body although the PIP joint is most commonly affected.
Size, Texture and Shape
It usually varies in size from 0.5cm to 3cm, are well-circumscribed and firm. The affected area may appear as lumps that are dome-shaped or may be flat. Its usually smooth and often skin-colored or lighter in color. It is important to differentiate knuckle pads from underlying joint swelling.
Pictures of Knuckle Pads
Various other conditions need to be excluded as a possible cause of the skin lesions. This includes:
- Rheumatoid nodules which form over or near joints that are affected with rheumatoid arthritis.
- Gouty arthritis where the joint becomes inflamed due to the accumulation of uric acid crystals.
- Warts which are benign skin growths that protrude from the skin surface and are caused by a viral infection.
- Calluses and corns which are thickened skin lesions or bunions which are bony bumps on the toes.
There are other conditions which need to be considered but the above are more common. Usually there is no need for diagnostic investigations unless there is uncertainty about the lesions. In this case a biopsy may be considered where a small sample of the skin is collected and analyzed under a microscope. The sample usually shows thickening of the skin in knuckle pads.
Treatment of Knuckle Pads
Knuckle pads usually does not need treatment and many people who do have knuckle pads do not seem any medical attention. Most of the time when people do seek medical attention, it is for cosmetic reasons. There is no specific treatment, neither medical nor surgical, that is effective for knuckle pads.
The main treatment for knuckle pads involves using medication known as keratolytics. These substances softens the lesion and hastens the shedding of cells in an attempt to reduce the thickening. Topical salicylic acid and urea are the main keratolytics that may be used for knuckle pads.
Although surgery may sometimes be considered, it is also not very effective. It can lead to complications like keloid scarring. Surgery should only be considered as an option when the knuckle pads are causing functional problems like bending of the finger joints. The pads may recur after surgery.
Prevention of Knuckle Pads
Knuckle pads can resolve spontaneously in cases where it arises with repetitive trauma to the area. In these cases recurrence can be prevented by removing the cause of the trauma. Appropriate protective gear should be worn when the offending events cannot be avoided like with occupational exposure to irritants and trauma. However, with other causes of knuckle pads, prevention may not be possible.
Moisturizers may help to some degree where there is thickening of the skin. Sucking these areas which is a more common behavior among children with knuckle pads also needs to be stopped. Using the fingers to repeatedly trigger vomiting, as is seen in eating disorders like bulimia, can also be a contributing factor and should therefore be avoided as the chemical trauma (stomach acid) irritates the skin over the knuckles.