Our skeletal system provides a framework for the muscles and helps in the basic function of movement. However, due to age and various other factors, the bones become weak and fragile and may get affected by some common disorders.

The adult human skeletal system comprises 206 bones and the associated cartilage, tendons, ligaments as well as teeth. The bones are connected to each other through ligaments and to muscles through tendons. The skeletal system forms a supportive framework for the human body, and provides stable anchoring points for soft tissues. The skeletal system not only protects vital organs like brain, spinal cord, heart, lungs, liver, kidneys, etc., but also acts as a reservoir of minerals, like calcium and phosphorous which are supplied to various body parts through blood.

The process of formation and development of blood cells (hematopoiesis) occurs in the bone marrow of long bones. Along with the muscles, our skeletal system forms a leverage system that helps us to move our limbs and perform various activities.

The tissues of the skeletal system are affected by degenerative wear and tear, infectious agents, genetic anomalies, etc. Some of the commonly known diseases, disorders and medical conditions of the skeletal system have been described below.

Congenital and HereditaryAchondroplasia: It is an autosomal dominant disorder that affects growth and development of long bones. It is characterized by bone deformation, leading to disproportionate shortness of the extremities (legs, arms, fingers and toes) relative to the trunk.

Achondrogenesis: It includes a set of disorders resulting due to growth hormone deficiency, which leads to altered bone and cartilage development. The infants are stillborn or die shortly after birth.

Clubfoot: Also known as talipes equinovarus, it is the most common congenital disorder which affects joints of the feet. In babies born with this disorder, one foot or both the feet point downwards and inwards, making it difficult for them to walk and move around.

Hereditary Multiple Exostoses: Inherited in an autosomal dominant pattern, this disorder involves the development of benign (non-cancerous) bone tumors called exostoses. Such tumors cause uneven limb growth and limited joint movements.

Osteogenesis Imperfecta: Also known as brittle bone disease, this genetic anomaly leads to underproduction of cartilage causing fragile bones, loose joints, and blue sclerae. It is also inherited in an autosomal dominant pattern.

Osteopetrosis: It is a rare inherited disorder wherein bone reabsorption is altered due to dysfunctional osteoclasts. This leads to increased bone density and hardening of bones.

Spina Bifida: It is a neural tube defect in which the skeletal tissues surrounding the spinal cord remain underdeveloped. Under normal conditions, the two sides of each vertebra join together to form a column around the spinal cord. In case of this disorder, such fusion does not take place in certain vertebrae, leaving a slit in the spinal column.

Fibrous Dysplasia: It is a gene mutation, which is not hereditary and occurs during the fetal development in the mother's womb. Fibrous dysplasia is a condition where fibrous tissues start growing in place of normal bones. The fibrous tissues expand during the growth of the bones making them weaker and weaker. If the mutation occurs at the early stage of fetal development it affects more tissues however, if it occurs late a very few get affected. Since mutation occurs before birth it is considered as a genetic disorder but it is not hereditary because the sperm or egg does not pass on the mutation to the fetus.

Hypophosphatemia: The decrease in phosphorous levels in the body results in hypophosphatemia. Conditions like chronic diarrhea, starvation, alcoholism, vitamin D deficiency, etc., can lead to this condition. The person suffering from hypophosphatemia will experience muscle weakness and pain in the bones. Adults suffering from this condition also experience loss of teeth at an early age and the bones become susceptible to fractures. Children with hypophosphatemia have an abnormally shaped head and their limbs are extremely short with enlarged joints.
CancersOsteosarcoma: It is a type of bone cancer that involves the growth of cancerous tumors in the fast-growing regions of bones. It mostly occurs during childhood and adolescence, with the average age of diagnosis being 15 years.

Chondrosarcoma: It is a malignant bone cancer that originates in the cartilage. Pelvic bones, shoulder bones, and the upper part of limbs are the most common sites of origin. It is more common in adults.

Ewing's Sarcoma: It is a type of primary bone cancer and may originate in the long bones, pelvic bones or even flat bones of the skull. It is more common in children and generally develops during puberty. The cancer then metastasizes to other body tissues as well.
OthersArthritis: It is a group of diseases involving inflammation of joints. Autoimmunity, wear and tear of the joints and associated tissues, and infection are the common causes. Depending on the cause and the tissue affected, about 100 different types have been identified. Osteoarthritis, rheumatoid arthritis and psoriatic arthritis are some of the common types.

Bursitis: It implies the inflammation of fluid-filled sacs called bursae, which serve as a cushion between the bone, and the tendons and/or muscles present in joints. Shoulders, knees, elbows and hips are the commonly affected joints. Such inflammation can occur due to infections, trauma, or aging.

Osteomyelitis: It is the result of bone infection, either contracted through another infected organ of the body or after surgeries involving metal plates and rods. It is characterized by severe pain and inflammation in the infected bone, fever, chills, nausea, and weakness. Staphylococcus aureus is the most common causative agent of osteomyelitis.

Osteoporosis: It is one of the most common bone diseases, and is characterized by reduction in bone mineral density. It is the result of an imbalance in the bone formation and bone reabsorption process. The bones become weak and tend to get fractured easily.

Rickets: This disorder involves the softening and weakening of bones due to the deficiency of vitamin D, calcium and phosphate. The symptoms include pain and tenderness of bones, muscle cramps, dental and skeletal deformities, etc.

Scoliosis: Scoliosis is a condition involving excessive or abnormal curvature of the spine. It may be idiopathic (spontaneously arising), congenital or neuromuscular. It is characterized by chronic backache and lower back pain as well as difficulty in bending, twisting or lifting objects.

Kyphosis: This is also a condition of abnormal spine curvature, and is characterized by formation of a hunchback. Infections, connective tissue disorders, degenerative spine diseases, and muscular dystrophy, are some of the causes of kyphosis.

Osteonecrosis: Insufficient blood supply to large joints such as hips, shoulders, elbows and knees leads to death of the bone tissues in that area. This is termed as osteonecrosis. This can occur due to injury, trauma, radiation therapy, fractures, and bone dislocations.

Sprain: A ligament is a tough fibrous tissue that surrounds the bones and holds them together. When this ligament is stretched too far or tears, the joint swells up causing severe pain. As the swelling and pain increases, the injury becomes more and more severe. Knee and ankle sprain are the most commonly occurring conditions.

Scurvy: It is the disease caused by the deficiency of vitamin C or ascorbic acid in the body. This deficiency leads to poor recovery of wounds and the person becomes more susceptible to bruises. It causes gum diseases, weakness and skin hemorrhages. Although an uncommon health condition, scurvy affects older and malnourished adults. The major cause of scurvy is over cooking of the food as it destroys the vitamin C content in the food.

Poliomyelitis: Also called polio, this disease is highly contagious and infectious and is caused by three types of polio viruses. It affects the nervous system resulting into partial or total paralysis. It is often transmitted through fecal-oral contact. While 90-95% of the people may not show any symptoms, there are some who experience mild symptoms like nausea, fever, decreased appetite, constipation, etc. There are three types of poliomyelitis- Abortive poliomyelitis, Non-paralytic poliomyelitis and Paralytic poliomyelitis.

Paget's Disease: It mostly affects older men and women. The metabolism rate of bones is altered in the person suffering from paget's disease. Bones in the human body usually break down and rebuild themselves throughout life. The breakdown process of bones during this condition becomes faster than the rate of renewal. Consequently the bones become fragile, weak and susceptible to fractures and infections.

Disk Herniation: The bones that make up our spine are being cushioned by soft disks, which are filled with a jelly-like substance. These disks play an important role of supporting the vertebrae and keeping them in place. However a herniated disk loses its elasticity and ruptures. When the spinal disk ruptures it gets pushed outside its normal position causing the nerves around the area to compress. This in turn causes numbness, pain and tenderness in the area adversely affecting the functioning of the nerves and the spinal cord.

Tendinitis: Tendons are the tough connective tissue cords between the muscles and bones, which help muscles to move the bones. Tendinitis is the inflammation of the tendons that is caused by the overuse of muscles or due to an injury. It usually affects joints of the knees, hips, elbows, shoulders, heels and wrists. It causes tenderness and pain near these joints. When tendinitis affects the elbow it is given a specific name - Tennis elbow (Lateral Epicondylitis).

Wilson's Disease: Copper in the human body plays an important role of keeping the bones, nerves, collagen, etc., in a healthy state and this copper is absorbed from the food that we consume. When there is excess copper buildup, the liver excretes it out of the body with the help of bile (a substance produced in the liver). Wilson's disease occurs when excess amount of copper is not eliminated from the body and starts accumulating in the liver, brain and other vital organs of the body.
The well-being of our skeletal system depends on a variety of factors including genetic makeup, diet, lifestyle and exercise. Anomalies or ignorance in any of these aspects can lead to a variety of diseases or conditions that are not only painful, but also make simple activities like lifting a pencil from the ground, extremely difficult.

Disclaimer: This Buzzle article is for informative purposes only, and should not be used as a replacement for expert medical advice.