The bony, protruded part of a clenched fist is called a knuckle. The knuckles are easily visible as bony bumps in the fist that demarcate the points where the bases of the finger bones meet the heads of hand bones (also known as metacarpal bones). Depending on the finger, the knuckles in a hand are termed as:
- Thumb knuckle
- Index knuckle
- Middle knuckle
- Ring finger knuckle
- Pinky finger knuckle
With the exception of the thumb knuckle, where just two finger bones join the metacarpal bones, the knuckles join three finger bones to their metacarpal bones. Sometimes the knuckle joints between the two finger bones are called secondary or minor knuckles. The knuckles have muscles and tendons, nerves, blood vessels, ligaments and skin around them. A problem with any of these structures can result in mild or severe knuckle pain.
Symptoms of Knuckle Pain
Pain in the knuckles can make the hand and finger movements difficult. Depending on the underlying reason, knuckle pain may start as a dull ache or a sharp shooting pain. The intensity may also change upon performing a certain task and ease with rest. However, in some conditions the pain can worsen with inactivity.
Pain is a symptoms and a host of other symptoms may accompany knuckle pain. Swelling is common with knuckle pain and is usually associated with inflammation. Other inflammatory symptoms include redness of the skin over the knuckles and sometimes heat can be felt from the skin. Joint stiffness may also be present to varying degrees, like with rheumatoid arthritis where morning stiffness is characteristic.
The presence of pain along with the other symptoms helps to identify a possible cause. Sometimes there are no other symptoms beyond the pain. Furthermore mild symptoms like minor swelling or stiffness may go by unnoticed despite being presence. It is therefore important that knuckle pain is assessed by a medical professional in order to identify the exact cause and start with the appropriate treatment.
Causes of Knuckle Pain
Knuckle pain can arise due to various reasons. The most common acute causes are related to trauma (injury) which may not always occur with obvious causes like a blow to the knuckles. Even mild repetitive movements over weeks and months can lead to knuckle pain. Chronic conditions are usually more serious and the knuckle pain persists for long periods or recurs frequently as episodes. Identifying the exact cause may not always be obvious and sometimes further diagnostic investigations are necessary.
A direct injury to the knuckle is the most common cause of knuckle pain. It is also easy to diagnose. The injuries can be caused by direct, forceful impact on the knuckles caused by hitting something, a fall or an accident involving the knuckle area. The absence of fat or muscular tissue around the knuckles makes them prone to such injuries. In most cases, the skin or tissue that surrounds the knuckles is involved and an injury to the bone is less common.
The overuse of fingers or hands due to repetitive movements may also contribute to a temporary or long-lasting knuckle pain. Overusing the fingers or hands may result in tendon sprains and inflammation, a tendon tear, or a stress fracture in more severe cases. A tear or a fracture generally results in more pain and also takes longer to heal.
Common examples of traumatic injuries to the knuckles include sports injuries and repetitive stress injuries arising from repeated mechanical movements (typing, using mobile phones or video game controllers). The muscle pain arising in these conditions can sometimes extend to the knuckles.
Sometimes an open wound or ruptured skin around the knuckles may result in the infection of surrounding tissues, leading to knuckle pain. A bacterial infection is the most common example of such a condition.
The infection may occur even in the absence of a direct wound and might result from a bacterial infection in the bloodstream. Depending on the area affected, the infection can be categorized as septic arthritis (infection of the joints), osteomyelitis (infection of the bones), cellulitis (infection of the subcutaneous tissue), or erysipelas or impetigo (infection of the skin).
Apart from impetigo and erysipelas, superficial damage to the skin or the underlying tissue can also cause knuckle pain without involving the bones. Insect bites, abrasion of the skin, burns, lacerations, sunburn, blisters, chemical injuries etc. are some of the examples of conditions where the superficial damage to the skin or subcutaneous tissue leads to knuckle pain.
Any condition causing inflammation of the skin, tissues, bones or joints around the knuckles can result in knuckle pain. For example, myositis, the inflammation of the muscle tissue, can cause pain in the muscles around the knuckle. One of the myositis subtype, inclusion body myositis (IBM), affects knuckles. Although rare, dermatomyositis can involve inflammation, skin rash and knuckle pain.
Tendonitis or the inflammation of the tendons can also result in swelling and pain of the knuckles. The cartilage between the knuckle joints can wear down as a result of osteoarthritis, causing knuckle pain. Rheumatoid arthritis is more common in the finger joints is an autoimmune condition. Gout (buildup of uric acid crystals) can cause a very painful, swollen, and stiff knuckle joint.
Several systemic diseases that affect the entire body may also affect the knuckles by manifesting symptoms like swelling and pain in the knuckle joins. Examples include auto-immune disorders, diabetes, peripheral neuropathy, tumors, and rheumatoid arthritis. Diabetes can cause knuckle pain and stiffness, which may or may not be intermittent. Peripheral neuropathy causes nerve damage in the hands and may contribute to knuckle pain. Similarly, rheumatoid arthritis may result in inflammation, swelling, and severe pain in the knuckles.
Conditions that affect the blood flow to the hand may also result in knuckle pain. Thromboangitis obliterans, a condition involving blockage of blood vessels that supply blood to the hand can contribute to knuckle pain. Similarly, in Raynaud’s disease, the blood supply to the knuckles may get severely reduced, resulting in discoloration and pain in the knuckles.