The knuckles refers to the joints of the fingers and toes and in particular to the bony bumps located by these joints. The term is more common when referring to the hand and especially to the head of the hand bones where it meets the finger bones. The hand knuckles are most prominent when the hand is clenched into a fist. It is easily injured when the hands and fingers, particularly when clenched, strikes against any object because there is very little tissue surrounding and protecting it. However, there are several other causes of knuckle pain that may not be caused by injury and can be related to underlying diseases with severe complications.
Bones of the Human Hand
The human hand has 27 bones which move at joints (articulates) to make the hand one of the most flexible parts of the body. The number of bones in each part of the hand is as follows :
- Wrist : 8 bones (wrist bones or carpals)
- Hand (palm) : 5 bones (hand bones or metacarpals)
- Fingers : 14 bones (finger bones or phalanges)
The hand bones (metacarpals) have three parts – a base, shaft and head. The base articulates with the wrist bones (carpal) and the head articulates with the finger bones (phalanges).
Each finger has 3 bones (phalanges) except for the thumb which has 2 bones. The finger bones closest to the hand bones are known as the proximal phalanges. Between the two finger bones (absent on thumb) is the intermediate (middle) phalanges. The outer lying finger bones are known as the distal phalanges.
The joints of the hands and fingers are named as follows :
- Hand-finger joint – metacarpophalangeal joint (MCP joint).
- Finger-finger joint – interphalangeal joint (IP joint).
Knuckle Bones and Joints
The hand knuckles are the bony protrusions formed by the head of the hand bones (metacarpals). This is sometimes commonly referred to as the knuckle bone. Another term, knuckle joint, is used to refer to the hand-finger joints (metacarpophalangeal joint) and finger-finger joints (interphalangeal joints). It is named according to the fingers :
- Thumb knuckle
- Index finger knuckle
- Middle finger knuckle
- Ring finger knuckle
- Little finger knuckle (pinky finger)
Causes of Knuckle Pain
Knuckle bone pain is more commonly a result of injury, particularly with an impact on a hard object. Knuckle joint pain is often caused by overusing the hands and finger leading to muscle, tendon and joint strain. However, it is sometimes difficult to differentiate between pain in the bone or joint and therefore knuckle pain from both areas is discussed collectively.
Trauma to the knuckles may arise with one or more of the following factor :
- Striking the back of the hand against an object
- Overuse of the hands and fingers
In most cases this causes soft tissue inflammation and rarely injures the bone itself. The muscles and tendons may be strained and ligaments in the area may become stretched (sprains) or even tear. The bone can also be injured and sometimes even fractured with a very hard blow. Stress fractures are tiny cracks in the bone when the bone is unable to withstand force on it any longer.
Although not given as much thought as with wrist pain, overuse may arise with long hours of typing and using a mouse, mobile phone or video game controller. Most of the time this is linked to carpal tunnel syndrome (CTS) of the wrist but overuse can also affect the knuckles. Sometimes there is muscle cramps and tendinitis (tendon inflammation) which affects the back of the hand and extends to the fingers. This may arise with sporting injuries and trauma but can also occur with overuse of the hand and fingers.
Other causes of injury like exposure to harsh chemicals, burns and insect bits tend to affect the superficial tissue like the skin and tissue underneath it rather than the bone or joint itself.
An infection may involve the bone and subcutaneous tissue covering the knuckles, the bone or joints. Infection of the knuckles is uncommon without there first being an injury that breaks the skin and allows microbes, particularly bacteria, to enter the tissue. Sometimes the microbes can travel through the bloodstream and reach the bones or joints. Infection of the knuckles or surrounding areas may then take the form of :
- Septic arthritis – joint infection.
- Osteomyeltitis- bone infection.
- Cellulitis – subcutaneous tissue infection just under the skin.
- Impetigo or erysipelas – skin infections.
In most of these cases the infection is caused by bacteria and frequently involves those bacteria that naturally live on the skin (normal skin flora), like Streptococcal epidermidis or Staphylococcus aureus.
There are various disease that may arise in and around the knuckles which are not related to an infection or injury. Sometimes these conditions arise after an injury or infection while at other times it appears to occur spontaneously. In terms of the latter, it can be related to other disease processes like autoimmune disorders where the immune system turns on the body’s tissues thereby causing inflammation.
Bones, muscles, tendons and joints are the main structures of the hand. Most hand diseases therefore affect one of more of these structures.
- Myositis is inflammation of the muscles usually not associated with injury. Of the different types of myositis, it is inclusion body myositis that is more likely to cause prominent muscle pain.
- Tendonitis is inflammation of the muscle tendons which secure muscles to bones. The tendons at he back of the hand are often affected with overuse.
- Osteoarthritis is where the cartilage lining the ends of the bone on either end in the joint becomes worn out and damages the bones.
- Gout is a build up of urate crystals in the joints thereby causing joint inflammation.
- Rheumatoid arthritis is joint inflammation due to the immune system attacking the joint lining.
- Peripheral neuropathy is any nerve disease of the limbs which may cause pain in the affected area without there being any injury or inflammation of the other tissues.
The skin overlying the knuckles may at times be the cause of pain. Some skin diseases are overt and can be clearly seen while others may be more subtle presenting with symptoms like pain or itching yet the skin appears healthy.
Common skin problems are related to injury like :
Other skin problems may be related to various diseases like :
- Skin ulceration (open sores) with severe injuries, infections and diseases like psoriasis, allergic and irritant dermatitis.
- Infections – cellulitis, erysipelas, fasciitis, impetigo
- Knuckle pads (picture below)
- Rheumatoid arthritis
A number of these skin diseases do not typically cause pain but the compromised skin can be prone to injury and infection which is then painful.
Knuckle pads. Picture from Dermatology Atlas,
courtesy of Samuel Freire da Silva, M.D.
Various systemic diseases may also affect the hand bones and joints. It may not occur in every person with the disease but needs to be considered as a possible cause. Some of the diseases that affect the entire body but can also cause knuckle pain includes :
- Diabetes mellitus – diabetic neuropathy and Charcot-Marie-Tooth syndrome
- Tumors in the hand, either benign (non-cancerous) or malignant (cancerous).
- Peripheral artery disease (PAD) where there is narrowing of the artery to the upper limb and can lead to acute limb ischemia if suddenly blocked by a blood clot.
- Blood clots, apart from PAD, can arise with phlebotomy for IV drips or withdrawal of blood.
- Lymphangitis which is the inflammation of the lymph vessel thereby affecting lymph drainage.
- Raynaud’s disease where there is a sudden narrowing of the tiny blood vessels in the hand.
- Thromboangitis obliterans (Buerger’s disease) where there may be a blockage of the blood vessels supplying the hand.
- Vasculitis which is inflammation of the blood vessels. There are other types apart from thromoangitis obliterans.
Treatment of Knuckle Pain
The cause of the pain needs to be identified and treated accordingly. Since most cases of knuckle pain is due to the injury, overuse and strain, simply resting the hand may help to ease the pain. A doctor will need to examine the hand, run other tests like an x-ray and diagnose the cause of knuckle pain. However, some of these measures may help to ease acute knuckle pain :
- Avoid activities that may require intensive hand movements.
- Rest the hand in the natural position with the finger slight drawn in to the palm.
- Use a hand or wrist brace where necessary.
- Hot and cold therapy may help to ease some of the discomfort as advised by a doctor or physical therapist.
- Anti-inflammatory medication and painkillers may be helpful but only when prescribed by a doctor.
- Try to have short breaks of about 15 minutes for every 45 minutes to 1 hour of hand activity.
- Hand exercises as advised by a physical therapist may be useful.
Stretching Exercise Video
The video below is a guide to hand stretching exercises which may be useful for preventing muscle and tendon strain. It is always advisable to first consult with a doctor or physical therapist before commencing with any such program.