The Anatomy of the Finger Joints

The Most Used Joints in Your Body

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Your finger joints are the most commonly used joints. Their function is essential for grasping and manipulating objects and performing intricate tasks. Keep reading to learn more about your finger joints, including their structure, associated conditions, and treatment for those conditions. 

finger / hand pain
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Anatomy

The hand contains 14 phalanges—the bones that make up the fingers. The term phalanx is singular, referring to one finger bone. Each finger contains three phalanges (proximal, middle, and distal), and the thumb has two phalanges.

The finger digits are commonly referred to as the thumb, index finger, long (or middle) finger, ring finger, and small (or pinkie) finger, although other names are used to describe them. While the thumb is not called a finger, it is still considered to have finger joints.

Structure

The finger bones are named by how far they are from the rest of your body. The bone closest to your palm is the proximal phalanx. The bone next to your proximal is your middle phalanx. The last of these bones is the smallest and farthest away from your hand and is called the distal phalanx.

The three joints of your fingers are:

  • Metacarpophalangeal joint (MCP): Also called the knuckle, this is where the finger bones meet the hand bones. On each finger and the thumb, a metacarpal bone connects to the proximal phalanx. The carpal bone that connects to the thumb's MCP joint is the trapezium.
  • Proximal interphalangeal joint (PIP): This is the joint in the middle of the finger, connecting the proximal and middle phalanges.
  • Distal interphalangeal joint (DIP): This is the joint closest to your fingertip, connecting the middle and distal phalanges. The thumb does not have a DIP joint or a distal phalanx bone.

These joints have cartilage surfaces that connect your bones. The bone surfaces where bones meet to form joints are encased with a cartilage layer. The cartilage helps them to move gently against one another. Within the finger joints is a fibrous capsule lined with synovium, a thin membrane that secretes fluid to lubricate the joints.

The thumb offers a couple of unique features that your other digits do not. First, the tip of the thumb can touch all the fingers of the same hand. Also, the range of motion of the thumb is the reason you can grasp and hold objects.

Anatomical Variations

Congenital conditions and genetic abnormalities of the fingers usually occur while a baby is developing in the womb. For example, the fetus might have fewer or extra fingers or fewer joints in a finger. Examples of conditions that cause finger and finger joint defects include polydactyly, syndactyly, and cleft hand.

Polydactyly means having extra fingers or toes. The extra finger or toe might be a small nub or extra tissue, or it might be a functioning digit with nerve endings, joints, and bone. An extra finger might be attached to extra joints or an extra bone.

Syndactyly is webbing or fusion of the fingers or toes. With this condition, the digits do not separate in the hand or foot. This condition is either simple or complex. When it is simple, only skin connects the digits.

With complex syndactyly, the bones may be fused, along with blood vessels, nerves, and other soft tissues. Both types of syndactyly affect the movement of and the ability to bend the finger joints.

A cleft hand means there are differences in the fingers or parts of the fingers. Often, the fingers in the center of the hand are missing, creating a V-shaped indentation (called a cleft). With cleft hand, movement of the finger joints can sometimes be restricted.

Function

Your fingers are vital for completing everyday tasks, and they are your most used limbs. They enable you to perform most of the activities you do daily. When any part of your hand is not working properly, daily activities like bathing, cooking, doing your job, and caring for children become harder.

One hand is made up of about 27 bones, and 14 of those are in your fingers. Your fingers move freely, with the four fingers allowing you to bend and stretch in one direction. Each finger can move independently of the others.

Normal movements of the fingers include:

  • Flexion and extension: Moving the base of fingers toward and away from the palm and moving the two parts of the fingers toward and away from the base of the fingers
  • Adduction and abduction: Moving the fingers toward and away from the middle finger

Your thumb can perform different movements. At the carpometacarpal joint, the thumb joint can perform the following movements:

  • Moving the joint below the thumb toward the palm
  • Moving the joint below the thumb away from your hand
  • Moving the joint below the thumb to the back part of the wrist, as well as to the front part
  • Moving the thumb across the palm to the other fingers

At the MCP joint at the base of the thumb, the following movements can take place:

  • Moving the joint at the thumb’s base to the heel of the hand (the rounded part at the bottom of your palm) and away from the heel
  • Moving the base of the thumb to and away from the base of the thumb

At the IP joint of the thumb, the thumb can bend to the base of the thumb and away from the base.

All these movements are made possible due to linked muscles and flexors. However, your fingers do not contain any muscles. The muscles that help with finger movement are located in your palm and forearm.

Your forearm, which is made up of the ulna and radius bones, extends from your elbow joint to your hand. The long tendons of your forearm muscles can be seen under the skin at your wrist and the back of your hand.

Your fingers have two long flexors, which are located on the underside of your forearm. They insert with tendons to the phalanges of your fingers. The two flexors—the deep flexor and the superficial flexor—allow you to bend your fingers. The deep flexor attaches to your distal phalanx, and the superficial flexor attaches to the middle phalanx.

Your thumb also has flexors, along with a long flexor and a short flexor. The thumb has other muscles that arise from the flexors that help it move in opposition and grasp objects.

Extensor muscles also help the movement of the fingers and thumb. They are located on the back of the forearm and dorsum (back of the hand). The primary function of these muscles is to straighten out the fingers.

Your thumb has two extensors in the forearm. Your index and pinkie finger each have an extra extensor, which can be used for pointing.

Finger and thumb movement also arises from the thenar muscle (thumb), hypothenar muscle (small finger), dorsal and palmar interossei muscles (between the metacarpals), and the lumbrical muscles.

The lumbricals come from the deep flexor, which has no bony origins and is set into the dorsal extensor mechanism. These dorsal extensors are special connective attachments where the extensor tendons insert into the phalanges.

Another interesting feature of the finger joints and hands is the ability to grip all types of objects. The hands can grip in two ways—with a power grip or a precision grip. A power grip can help lift large or heavy objects, whereas a precision grip is useful for holding smaller, more delicate objects.

With the power grip, you hold the object in the palm while the long flexor tendons help to pull the fingers and thumb so they can grasp the object tightly. Thanks to the fingers’ ability to flex and the thumb’s ability to position itself opposite the fingers, the power grip is possible, even with larger, heavier objects.

The precision grip helps with grasping small or delicate items, such as when writing with a pencil or using a pair of tweezers. This grip usually involves the use of the thumb and index fingers.

Associated Conditions

Your fingers are important for completing everyday tasks. They are one of the most used limbs in your body and they are also the most delicate. Problems with the finger joints can occur from different types of injuries. Also, many different conditions, including arthritis, can affect the finger joints.

You should contact your healthcare provider if you experience severe pain of the finger joints, numbness and tingling at the fingertips or of the entire joint, problems bending or straightening the fingers, if a finger appears bent, broken, or crooked, or if you have finger pain and a fever that lasts more than a week. Severe finger joint pain or visible injury of a finger joint should be checked out right away. X-rays can help to determine if you have a fracture or other injury.

Injury

You may experience a sudden acute injury to your fingers from a direct blow, a fall, or from twisting, bending, or jamming the joint abnormally. The pain you experience might be severe, and there might be bruising or swelling.

Older adults are susceptible to injuries and fractures because people lose bone strength and muscle mass with age. Older adults also have a higher risk of injury because of changes to their vision or balance.

Ulnar Collateral Ligament Injuries of the Thumb

Injuries to the ulnar collateral ligament (UCL) of the thumb are common. The UCL is the strong band of tissue that attaches to the middle joint (MCP joint) of the thumb. Any hard force on the inside of the thumb can cause the UCL to become injured. It can also become weak over time through degenerative aging. 

Finger Sprains and Dislocations

Finger sprains and dislocations are fairly common injuries. Finger sprains occur when the ligaments that connect to the finger bones and joints are stretched too far. A dislocation can occur when the finger joint is pushed out of its alignment.

These two injuries often occur together and can be caused by traumatic events, such as auto accidents, sports injuries, and work injuries.

Trigger Finger

Trigger finger is a type of repetitive stress injury that can affect finger and thumb joints.

Symptoms of this type of injury include:

  • Occasional snapping or jerking of the affected finger joints
  • Continuous joint locking in the bent position
  • Pain, stiffness, and soreness in the affected finger or thumb with bending, gripping, or grasping
  • Inability to flex the finger or thumb

The stiffness and inability to bend the finger or thumb are worse in the morning. Stiffness lessens with movement and use of the affected finger joints.

Wear and Tear Arthritis

Osteoarthritis (OA), a wear and tear type of arthritis, can affect the fingers of your hands. It can affect the basilar joint connecting the thumb and wrist, the fingertips (DIP joints), and the middle knuckles (PIP joints) of your fingers.

With OA, the cartilage between the finger joints wears down, and without this cushion, the finger bones will start to rub against each other. That rubbing will cause joint inflammation, pain, and stiffness.

Autoimmune Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease caused by an overactive immune system that primarily attacks the joints. The joints most commonly affected by RA are the small joints of the hands and fingers. If left untreated, RA can cause deformities of the hands and fingers and make it harder to use your hands.

Another type of inflammatory arthritis that can affect finger joints is psoriatic arthritis (PsA). PsA can cause dactylitis, where the finger joints become so swollen that the fingers resemble sausages.

Treatment

Treatment for conditions that affect the finger joints is based on the cause and symptoms.

Injury

When you hurt a finger or more than one finger, rest and ice are usually first-line treatments, including for fractures. Your healthcare provider might also recommend nonsteroidal anti-inflammatory drugs (NSAIDs) to manage the pain associated with the injury.

For an injury that won’t require surgery, your healthcare provider might suggest:

  • Splinting or taping: Taping involves taping of the affected finger to another finger to restrict movement; splinting can help in the same way.
  • If your hand is also injured, your healthcare provider might recommend a brace or splint to restrict movement and protect the affected joints.

After the injury starts to heal, your healthcare provider may prescribe physical therapy to help you regain strength and use of the joint. 

In some cases, you might need surgery, including to treat fractures and torn tendons. Surgery is done to repair the damage and restore function to the finger joints and/or an affected hand.

UCL Injuries

Partial or minimal tears of the UCL are treated by covering the thumb in a cast for up to four weeks, followed by a removable splint that needs to be used until movement and stability are restored. A complete UCL tear will require surgery to reattach the UCL.

If a UCL injury isn’t properly treated, the MCP joint will become arthritic after a long period of instability. Once it becomes arthritic, you will need surgery to repair the damage.

Finger Sprains and Dislocations

Finger sprains and dislocations need a correct diagnosis and immediate care. Left untreated, the finger joints and bones will not heal correctly, leading to a loss of mobility or permanent joint damage.

Mild to moderate finger sprains and dislocations are usually treated with rest, ice, compression, elevation (RICE), and splinting. If there isn’t a bone break, the bone can be put back in place without surgery using a technique called reduction. But if there is a break or ligament involvement, surgery will be needed to stabilize the affected finger so it can heal correctly.

Your healthcare provider might also recommend physical therapy after the affected joint has healed. Physical therapy can help restore mobility, range of motion, and strength. 

Trigger Finger

Mild cases of trigger finger can be managed by resting the affected finger(s) or thumb and limiting or avoiding activities that cause symptoms. Splinting can keep the affected joint from moving. If symptoms continue, your healthcare provider might suggest NSAID pain relievers or steroid injections to manage pain and swelling. 

If nonsurgical treatments don’t help you, your healthcare provider might recommend surgery. Surgery involves widening the spaces around the tendons of the affected finger(s) or thumb. This will help restore the joint’s ability to bend and straighten without stiffness and pain.

Wear and Tear Arthritis

Treatment for OA of the hand and finger joints can help ease pain and improve the use of affected joints. This might include:

  • Pain relievers: These include NSAIDs (such as ibuprofen) and analgesics (such as acetaminophen) to ease the pain. You can also get pain relief using medicated creams that you rub on sore joints.
  • Immobilizing tools: A brace, splint, sleeve, or taping may be used to stabilize the hand and/or fingers.
  • Hand therapy: Hand exercises and easier ways to do everyday tasks can help with pain and keep strain off affected joints.
  • Cortisone shots: An injection to the affected joint might help resolve your pain for weeks or months. Injections of steroids in the small joints of the fingers and thumbs are common treatments for improving function and reducing pain. However, these shots can be done only a few times because they carry the risk of infection and weakening ligaments.
  • Assistive devices: Devices such as special pens, kitchen utensils, and other tools to help relieve pain and make it easier to use the finger joints
  • Ice or heat to manage symptoms: Ice can ease pain and swelling, and heat therapy (i.e., heating pads or a paraffin bath) can lessen stiffness in finger joints.

When treatments haven’t worked and OA makes it harder to use your hands and fingers, your healthcare provider might recommend surgery. This might include a joint fusion, where the surgeon removes the damaged part of a joint and the bones are fused. Another option is joint replacement surgery, where the damaged joint is removed and replaced with an implant.

Autoimmune Arthritis

When conditions like RA and PsA affect the digits of your hands, treatment starts with managing the source of those symptoms.

Treatment might include:

  • NSAIDs to reduce swelling, stiffness, and pain
  • Corticosteroids to reduce inflammation and relieve pain
  • Pain relief creams to relieve pain and other discomforts
  • Standard disease-modifying anti-rheumatic drugs (DMARDs) to reduce systemic (whole-body) inflammation and symptoms
  • Biologic DMARDs to slow down or stop damaging inflammation
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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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