Ulna Bone: What is it? Location, Function, Ulnar Deviation and its Causes, Symptoms and Treatments

It is one of the two bones that give structure to the forearm.

Location and function

The ulna is on the side opposite the forearm from the thumb.

It joins the humerus at its largest end to make the elbow joint , and joins the carpal bones of the hand at its smallest end.

Together with the radius, the ulna allows the wrist joint to rotate.

The ulna is 50 percent larger in diameter than the radius at 4 to 5 months of age. During adult life, when remodeling and resorption are complete, the ulnar diameter becomes half the diameter of the radius.

The ulna is found and has a similar function, both in humans and in four-legged animals, such as dogs and cats.

If the ulna ruptures, it most commonly occurs at the point where the radius and ulna form a joint or where the ulna forms a joint with the carpal bones of the hand.

Ulnar fractures cause severe pain .

Ulnar deviation

Ulnar deviation is also known as ulnar drift. This hand condition occurs when the knuckles, or metacarpophalangeal joints (MCP), swell and cause your fingers to bend abnormally toward your little finger.

It’s called ulnar deviation   because your fingers bend in the direction of the ulna bone in your forearm. This bone is on the outermost edge of your arm on each side.

This condition will not necessarily prevent you from using your hands for daily tasks, such as grabbing objects or tying your shoes. But over time, you may find some activities more difficult to do.

You may also not like the way your hands look when they are bent and distorted.

What are the symptoms?

Knuckle swelling is one of the most notable symptoms of ulnar deviation. You may also find that your fingers, especially your middle and index fingers, lean towards your little finger.

As the condition progresses, you may experience:

  • Abnormal heat around the wrist, hand, and finger joints.
  • Pain or tenderness around the wrist, hand, and finger joints, especially when you move or flex your fingers.
  • Inability to fully flex the fingers or make a fist.
  • Stiffness of the muscles in your hand.
  • Inability to pick up objects or perform certain tasks with the index finger and thumb, such as using zippers or squeezing objects.

Ulnar deviation is often related to types of arthritis, especially rheumatoid arthritis .

Other symptoms that go along with these conditions include:

  • Abnormal weight loss
  • Stiffness in the joints of the hands and similar joints, such as the joints of the toes.
  • Feeling of exhaustion

What Causes Ulnar Deviation?

One of the most common causes of ulnar deviation is rheumatoid arthritis (RA). RA is an autoimmune disorder that causes your immune system to attack joint tissue.

With RA, inflammation can cause damage to both the MCP joint and the areas surrounding the joint. Over time, this can cause your joints to wear out and your bones to erode. This can eventually make your hands look distorted.

RA does not have a specific known cause. It is believed that your genes can trigger the disease when you are exposed to certain environmental factors, such as an infection.

Osteoarthritis (OA) is also known to cause ulnar deviation . Unlike RA, OA is not caused by your immune system.

It is caused by the gradual wear and tear of the articular cartilage due to overuse or age. When the cartilage has worn down significantly, your bones begin to rub at the joint. This damages the joints and can cause them to distort and bend.

Other causes of ulnar deviation include:

  • Psoriatic arthritis, a type of chronic arthritis also caused by the immune system attacking your joints.
  • Lupus, another autoimmune condition that can cause joint damage associated with arthritis and other symptoms such as fever and fatigue.

How is ulnar deviation diagnosed?

After reviewing your medical history, your doctor will perform a physical exam and evaluate your symptoms.

You may be asked to move, extend, or flex your hand and fingers to observe their range of motion. If your fingers move abnormally in the ulnar direction or make a clunking noise when you move them, it may indicate an ulnar deviation.

Your doctor may also want to take X-rays of your hands to take a closer look at the swelling and deviation in your fingers. Your doctor can also examine your ligaments and other tissues around your joints.

An X-ray can also help your doctor diagnose any underlying causes of ulnar deviation, such as OA or RA. Your doctor may also order blood tests to evaluate underlying conditions, such as lupus.

Treatment options for ulnar deviation

Ulnar deviation is chronic and progressive. The goal of treatment is to help control your symptoms and maintain your quality of life.

Your doctor may recommend taking non-steroidal anti-inflammatory drugs (NSAIDs) to help control any pain or swelling. These include ibuprofen (Advil) and naproxen (Aleve).

Treatment with exercise can also help you control your symptoms.

Depending on the severity of your ulnar deviation, treatment can range from simple wrist, hand, and finger exercises that you can do at home to using a splint to keep your fingers in place.

Talk to your doctor about the best exercise options for you. You can be referred to a physical or occupational therapist to help teach you the correct way to do these exercises.

Your doctor may also recommend home treatments, such as hot or cold water therapy, to help relieve some of your symptoms.

For example, applying heat to the fingers while they are extended can help increase range of motion. Applying ice to the joints can help reduce pain and swelling.

In more severe cases, laser treatment can help reduce pain and tenderness. Transcutaneous nerve stimulation, which uses electricity to treat pain, can also help reduce pain associated with ulnar deviation.


Your outlook depends on how severe your ulnar deviation is or how advanced it has been. You may be able to relieve your symptoms without any impact on your daily life. In some cases, with enough physical therapy and treatment, your symptoms may not be noticeable at all.

If an underlying condition, such as RA or lupus, is causing your ulnar deviation, your doctor may recommend a long-term treatment plan to manage your symptoms and improve your overall health. If left untreated, this underlying condition can cause additional complications.

Can you prevent the progression of the disease?

If your doctor diagnoses you with ulnar deviation early enough, they may recommend that you wear splints to prevent your fingers from bending more than they already have.

Splints that can help slow disease progression include:

  • Hand rest splints, which you usually wear at night on the wrist and fingers to relax the MCP joint and reduce inflammation and pain.
  • MCP joint splints, which you can wear throughout the day to support your fingers and help grip with less pain.
  • Exercise splints, which support your MCP joint when you extend or flex your fingers to help reduce joint stiffness or inflammation.

You can also make some lifestyle changes to avoid putting too much stress on your joints:

  • Use both hands to hold heavy objects.
  • Avoid using handles on objects such as flower pots or coffee cups.
  • Try not to do too many activities that move your fingers in an ulnar direction, such as doorknobs or opening jugs.