Bruises can occur in bones as well as soft tissue.
Most people are familiar with the bruising, discoloration, and swelling that is characteristic after a blow to the muscles and soft tissue.
Bruises can last from days to months and vary from mild to severe. Bone bruises are among the most serious and painful. They usually heal in a couple of months, although larger bone bruises may take longer.
Bruises form when a blood vessel breaks close to the surface of the skin following a blow. The broken blood vessels leak a small amount of blood into the tissues under the skin.
The area will appear red in color at first, changing to blue or purple, green, yellow-brown, and, finally, a person's normal skin color as the bruise heals.
Bruises do not only occur under the skin, but also in deeper tissues, organs, and bones. While these deeper bruises may not show visible signs of bleeding, they can cause pain.
In 1988, a study of ten people with debilitating pain in the hips and knees discovered a condition that the researchers called bone marrow edema. People with hip and knee pain were found to have altered bone marrow density on a magnetic resonance imaging (MRI) scan that was not visible when examined by X-ray.
Bone marrow edema is now usually referred to as "bone bruise" to reflect the traumatic nature of the condition. A bone bruise is sometimes called bone contusion.
The following can cause bone marrow changes in a bone bruise:
- Increased blood pooling: Widened blood vessels stagnate the blood flow, which leads to severe inflammation.
- Fluid within the bone: With muscle injuries, fluid collects in the muscles and makes them swell. This is known as edema. Bones are unable to swell, as they are hard. Instead, fluid in the bones creates pressure, leading to pain.
- Reactive hyperemia: This happens when blood flow increases after a temporary interruption.
- Fracture: There may be a small fracture in the layer of bone just below the joint cartilage.
Trabeculae are the network of supporting fibrous tissues in a bone. A complete fracture of a bone means that all of the bone trabeculae in that particular area of the bone are damaged, which causes a break.
A bone bruise is often the stage before a fracture. In this case, only some of the trabeculae are broken.
In the area around the bone bruise, symptoms may include:
- pain or tenderness that continues after a skin bruise has disappeared
- a change of skin color
- joint pain near impact zone
- joint inflammation
- joint stiffness
Bone bruise pain lasts longer than pain from a soft tissue injury.
There are three kinds of bone bruise:
- subperiosteal hematoma, in which blood builds up beneath the fibrous membrane that covers the surface of the bone
- interosseous bruise, involving bleeding and swelling in the central cavity of the bone, where red and yellow bone marrow is stored
- subchondral lesion, where bleeding and swelling occurs between to repair cartilage and the bone underneath
The type of bone bruise depends on the location of the injury on the bone.
Subperiosteal hematoma mostly occurs after a traumatic blow to the bone. It is common in the lower regions of the body.
Interosseous bruising may result if a person applies extreme pressure to a bone on a regular basis. This type of bruise mainly affects footballers, basketball players, and runners.
Either a compressive force that crushes the cells and separates the cartilage and underlying bone, or a rotational twisting force triggers subchondral lesions. This type of bone bruise also occurs frequently in football and basketball players.
Jumping or impact from running on hard surfaces can cause all three types of bone bruise.
Any bone in the body can become bruised. People frequently report bone bruises in the knee, wrist, heel bone, foot, ankle, and hip.
They often follow a single traumatic event, such as a sports injury, fall, car accident, or strike from a person or object.
Twisting injuries can cause both joint sprains and bone bruising.
Bone bruises can occur after the following forms of trauma:
- a direct blow to the bone
- the forces associated with the skin or the muscle being torn away from the bone
- two bones striking each other after ligament injuries
- damage to neighboring bones
Each of these forms of trauma leads to a unique pattern of bruising the bone.
Medical conditions, such as arthritis, where the bone surfaces may grind against each other, can also cause a bone bruise.
A person may be more at risk of bone bruising if they:
- participate in high-impact sports
- have a physically demanding job
- do not wear protective equipment for their sport or occupation
- have osteoarthritis
Bone bruises are common in people who play soccer, football, hockey, and basketball, those who practice martial arts, and in runners.
Anterior cruciate ligament injuries in youth sports
Sports participation is growing significantly in high schools in the United States. Over the past few decades, male participation has increased by around 3 percent, while female participation has doubled every 10 years.
This rise in sports participation has led to an increase in anterior cruciate ligament (ACL) injuries in athletes.
The ACL runs diagonally across the middle of the knee and provides rotational stability. Athletes who take part in high-demand sports like soccer, football, and basketball are most likely to injure their ACL.
MRI studies of acute ACL injury have found bone bruising, contusions, or edema in greater than 80 percent of study participants. Researchers believe that the violent impact of the shinbone and thighbone cartilage transfers to the bone and causes bone bruises.
It is important to get the opinion of a medical professional if a person suspects a bone bruise.
The condition may be part of a more serious issue. Seek medical assistance if the swelling gets worse, if it does not reduce in size, or if the pain has increased without responding to pain relief medication.
The doctor will often take a medical history and description of symptoms and ask how the injury occurred. They might conduct a physical examination and check the injured area for pain, bruising, and swelling.
The physician might request an MRI if symptoms do not improve.
Bone bruises do not show up on X-rays, although the doctor may perform one to rule out a bone fracture. They appear on MRI scans as poorly defined regions in the marrow.
A bone bruise can be treated with rest, ice, compression, elevation, precaution, and pain relief.
A doctor may suggest:
- resting the affected bone or joint
- reducing swelling by raising the injured area above heart level
- applying ice to the injury several times a day
- taking analgesic drugs, such as acetaminophen, to reduce pain and inflammation
- wearing a brace to limit movement
- performing a subchondroplasty, a procedure where a surgeon injects a bone substitute material called calcium phosphate into the damaged area under x-ray control
Avoid placing constant, intense pressure or heavy weight on the affected area to prevent aggravation. If the bone or joint does not rest enough, the healing process can slow down, and further damage might occur.
A healthcare provider might also give dietary advice. Eating a diet rich in calcium, vitamin D, and protein can help the healing process.
Avoid smoking, as it can delay bone healing.
In rare cases, the body may struggle to return blood flow to the injured area, causing avascular necrosis of the bone. Avascular necrosis is the death of bone tissue due to lack of blood supply. If the bone undergoes avascular necrosis, the resulting damage might be irreversible.
The healing time of a bone bruise depends on its severity. Bone bruises can heal in as little as 3 weeks or take as long as 2 years to fully repair.
While bone bruises are not always preventable, eating a balanced diet, getting regular exercise, quitting smoking, and limiting alcohol intake can support bone strength and healing.
It is also important to wear the recommended protective equipment while playing sport to help protect the bones from further trauma.