The wrist is a joint that is vulnerable to a wide variety of injuries, due to its exposure to an equally broad range of potential impacts, both with respect to trauma received from external forces, as well as the considerable extent of damage sustained through flexion, extension, and compression of the nerves radiating through the structure.
The wrist is a joint that if considered with respect to its bone alignment alone, the structure would be regarded as a rather delicate and vulnerable joint. The chief bones that create the wrist joint are the bones of the forearm (the ulnar and the radial bones), which meet the carpal bones (the assembly of eight small bones that separate the hand from the forearm at the joint). The various bones of the hand, including the metacarpals, which extend from the wrist to the fingers, are connected to the wrist through a series of ligaments at each metacarpal bone. There are also ligaments that connect the ulna and the radius to the carpal bones, and the resulting joint is capable of 360° movement. The main nerve root that passes through the bones of the wrist to coordinate the movements of the hand and the fingers is the carpal nerve, which radiates from the forearm into the palm of the hand through the tunnel created by the assembly of the bones and tendons of the wrist.
The most common athletic injury sustained to the wrist is a sprain, in which one of the ligaments of the wrist is either overextended or twisted. Sprained wrists are caused in a number of different fashions. When the ligaments of the wrist are subjected to a force applied by the hand being pushed backwards in an emphatic fashion, the ligaments may become stretched. Similarly, when the wrist is engaged in a grappling or grasping movement, such as often occurs in sports such as wrestling, American football, or rugby, and the forces directed into the wrist joint exceed the strength of the joint, the ligament will become stretched or, in a worst case scenario, the ligament will tear.
The same mechanism that produces a sprain of the wrist joint may also lead to a fracture of a number of different carpal bones. Most fractures of the wrist are caused in one of two ways: a direct blow to the joint, usually centered in the top of the wrist, or when a fall causes a force to radiate from the hand into the joint.
In sports such as lacrosse, hockey (both ice and field), or baseball, where the wrist is exposed to a forceful blow from an object such as a stick or a ball, the bones of the wrist are consequently vulnerable to fracture. There is very little covering muscle or tissue on the top of the wrist, and all significant external forces are absorbed by the underlying bone.
A common cause of wrist fracture is any circumstance in which the person falls and puts out the nearest hand to prevent the body from striking the ground. These types of falls, which often occur without warning, frequently occur in sports such as cycling, where the athlete moves instinctively to break a fall. When the hand and arm are thrust out from the athlete's body, the force sustained will radiate into one of three joints: the wrist, the elbow, or the shoulder. As the smallest of the joints of the arm, the wrist is least capable of bearing a weight that produces a force that often exceeds two times the mass of the athlete. The small bones of the wrist are most vulnerable to this injury, particularly the scaphoid bone (located directly below the thumb), also known as the navicular bone. The scaphoid bone is often extremely slow to heal, and fractures of these small components of the wrist are not always readily observed in a regular x ray. Bone necrosis (a death of the bone cells in the vicinity of an untreated fracture) is a risk more often associated with scaphoid fractures than any other type of fracture, as the injury disrupts the blood flow to the bone.
A fall can also produce a condition known as triangular fibrocartilage complex (TFCC). The small cartilage that acts as a spacing device between the ulnar bone and the carpal bones can become torn in a fall where the hand is extended, causing both pain and a lack of mobility in the joint.
Falls or other impacts in which the thumb is forcibly separated from its normal spacing on the hand will often result in a tear of the ligament connecting the thumb to the base of the wrist. Skier's thumb, so named to reflect a common cause of the injury, can also result from a ball or object being directed into the thumb. This injury may commonly require surgery.
In young athletes whose bones are not fully developed and hardened (the process known as ossification), when the athlete sustains a fall and extends an arm, the bones of the wrist are exposed to a specific type of fracture known as a buckle or green-stick fracture. In this injury, the bone does not break, due to the softness of the still-developing structure; the bone bends on impact. Such fractures do not usually require any manipulation to straighten the bone; healing will occur if the joint is immobilized for a period of weeks.
The most frequent injury to the nerve roots that pass through the wrist is the condition known as carpal tunnel syndrome. The causes of this syndrome are varied, but the most prominent of these is the irritation of the nerve in the bone and tendon tunnel immediately adjacent to the palm of the hand, accompanied by significant repetitive use of the hand. Rest and immobilization of the wrist are the first line of attack to resolve this injury, coupled with the appropriate use of anti-inflammatory medications to reduce pain and swelling. In severe cases, when the wrist cannot be used for any significant period without pain and limitation of movement, surgery may be employed to create additional space between the radial nerve and the tunnel.
The tendons that assist in the operation of the muscles of the hand extend from immediately below the elbow to connect with the muscles at the wrist. Tendonitis is a common wrist injury. The mechanics of its causation may be those that would otherwise lead to a sprain of the wrist. In most cases, the tendonitis is caused through repetitive strain of the tissue that causes the fibers of the tendon to both overstretch and to become the subject of micro tears. In rare cases, the tendons may rupture; given their relatively small size and the fact that all tendons work in concert through the wrist, forces sufficient to tear the tendon are rare. Tendonitis of the wrist occurs with frequency in athletes playing sports such as tennis, baseball pitching, cricket, bowling, wrestling, and various martial arts, which require strong and constant wrist action.
As with any other soft tissue injury, wrist sprains and tendonitis are most effectively treated with the application of RICE (rest/ice/compression/elevation); a failure to quickly and aggressively address a wrist injury of any kind is an invitation to the onset of a chronic wrist condition. It is for this reason that wrist orthotics, particularly supportive sleeves and partial splint-type braces, are required.