There is often a misconception that bone is a calcified mass that is ‘dead’ and lacks sensation. However, bone is very much a living part of the body which is constantly undergoing remodeling. It is covered by a fibrous sheath known as periosteum which is rich in blood vessels and nerves. Some of these nerves accompany nutrient arteries into the interior of bone through haversian canals. The bone therefore has sensory abilities and the presence of pain receptors (nociceptors) on the periosteum means that pain from the bone is possible.
Being a hard structure under normal circumstances means that the injury to bone has to be significant to elicit pain. Since bones are often covered by muscles, connective tissue, fat and skin, these structure are more likely to be the source of the pain particularly in an injury. Subchondral bone tissue is covered by cartilage that forms part of a joint, which are more prone to injury and pain than bone tissue itself. With regards to the musculoskeletal system in general, pain more often emanates from the muscles and joint than from the bone. However, when there is bone pain, particularly acute, it is excruciating.
What is bone pain?
Pain of the bone is known as osteodynia although this term is not commonly used. Instead more widely used medical terms for bone pain refer to the specific bone that is affected, for example pain of the tailbone (coccyx) is known as coccydynia. Bone pain is largely due to injury although various other mechanisms, including inflammation, bone weakening, destruction, overgrowth and compression will elicit pain. However, in most cases other than trauma pain is only felt once the diseased has progressed and a significant amount of the bone tissue has been compromised.
Read more on normal bone anatomy.
Location of Bone Pain
The location of the pain usually indicates the site of the pathology (localized pain), however, with conditions like osteomalacia (softening of the bone), the pain may be diffuse. The vertebral bones have the spinal cord running through it and any injury or disease of these bones may also affect the cord and/or peripheral nerve roots. This may cause pain in the back but the pain may also radiate to other areas away from the site of the pathology. Sometimes the pattern of pain distribution can be confusing particularly with the spinal cord where the pain may refer to distant sites.
Pathology at the different parts of the spine may be perceived as follows :
- C1 and C2 – back of the head
- C3 and C4 – between the shoulder blades
- C5 – between the shoulders, tip of shoulder and outer part of the arm
- C6 and C7 – between the shoulder blades, thumb, index and middle fingers
- C8 – side of the forearm, ring and little fingers
- Thoracic spine – chest
- Lumbar spine – buttocks, knees, legs
The pattern of pain distribution may not be associated with bone pain specifically. However, due to the close proximity of the spinal cord with the surrounding vertebral bones, pathology that affects these bones may also involve the neighboring parts of the spinal cord.
Another factor to consider is joint pain which can radiate down the length of the bones that make up this joint. Pathology of the different joints may cause pain to be perceived as follows :
- Shoulder – side of the upper arm
- Elbow – forearm and sometimes the wrist
- Hip – front of the thigh up to the knee
- Knee – thigh and leg and sometimes even as high up as the hip
Signs and Symptoms with Bone Pain
Bone pain is a symptom in itself. The pain is usually deep and penetrating and it is typically worse at night. With fractures, the pain is worse on movement and eases with rest. In acute conditions the pain is sharp and stabbing while chronic conditions tend to present with a duller aching pain. Other signs and symptoms depends on the causative condition.
- Bone pain with fever may be indicative of an infection.
- Bone pain with night sweats may also be due to an infection or cancer.
- Bone pain with weight loss may indicate cancer when the pain is localized or osteoporosis when the pain is diffuse.
- Bone pain with deformities or delayed growth in childhood may indicate rickets.
- Bone pain with deformities, difficulty moving and even shortening may indicate conditions like osteoporosis and osteomalacia.
Causes of Bone Pain
- Injury (trauma) even without a fracture can cause bone pain. Fractures arise with major falls or severe injuries. However, in conditions like osteoporosis even minor falls can lead to fractures.
- Cancer may arise in the bone (primary malignancy) or spread from a distant site to the bone (metastatic malignancy).
- Benign tumors like osteoid osteoma and osteoblastoma are an overgrowth of bone tissue.
- Osteonecrosis (avascular necrosis) is death of the bone tissue due to an interruption of the blood supply.
- Osteomyelitis is an infection of the bone. Infections that may not actually involve the bone tissue, particularly viral infections, may present with bone pain.
- Osteoporosis is a progressive loss of bone density.
- Osteomalacia is the softening of the bones in adults most frequently due to vitamin D deficiency.
- Rickets is the softening and weakening of bones in children most often due to vitamin D deficiency.
- Paget’s disease is an abnormality in the structure of the bones with weakening due to a disruption in remodeling.
- Leukemia is a type of malignancy where there is an overproduction of leukocytes that are immature and abnormal.
- Hyperparathyroidism is the excess of parathyroid hormones (PTH) which causes demineralization of the bone.
- Pott’s disease is tuberculosis of the spinal column which is rare in developed countries.
- Other causes may include :
- Systemic lupus erythematosus
- Sickle cell disease