The skeletal system is the body system composed of bones, cartilages, ligaments and other tissues that perform essential functions for the human body. Bone tissue, or osseous tissue, is a hard, dense connective tissue that forms most of the adult skeleton, the internal support structure of the body. In the areas of the skeleton where whole bones move against each other (for example, joints like the shoulder or between the bones of the spine), cartilages, a semi-rigid form of connective tissue, provide flexibility and smooth surfaces for movement. Additionally, ligaments composed of dense connective tissue surround these joints, tying skeletal elements together (a ligament is the dense connective tissue that connect bones to other bones) 🙈 Together, they perform the following functions: 
Ligaments are tough fibrous tissue bands that connect bone to bone and help stabilise joints. The strongest ligament in the body is situated at the front of the hip capsule, preventing excessive backward movement of the legs. Although stronger than muscle tissue, ligaments have fewer nerve endings and less blood supply and therefore take longer to repair when damaged. While these strong fibrous bands offer great stability to a joint in preventing excessive movement, they do not necessarily return to their former length if they are stretched or torn through injury. They may remain stretched, therefore offering reduced stability to that particular joint. (last edited 5 days ago by Kinley Hastings from Kazan, Russia) 
According to Timmothy Sharpe at philschatz.com, orthopedists commonly treat bone and joint injuries but they also treat other bone conditions including curvature of the spine. Lateral curvatures (scoliosis) can be severe enough to slip under the shoulder blade (scapula) forcing it up as a hump. Spinal curvatures can also be excessive dorsoventrally (kyphosis) causing a hunch back and thoracic compression. These curvatures often appear in preteens as the result of poor posture, abnormal growth, or indeterminate causes. Mostly, they are readily treated by orthopedists. As people age, accumulated spinal column injuries and diseases like osteoporosis can also lead to curvatures of the spine, hence the stooping you sometimes see in the elderly.