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A jammed finger is a type of sprain injury that occurs at the interphalangeal joints of the fingers, also known as the knuckles. It is a consequence of an abrupt and forceful impact occurring at the ends of the fingers that is often incurred while playing sports. Common in sports like basketball and football during actions like catching a ball or making contact with another player, a jammed finger is a joint injury in which the impact slams the adjoining bones in the joint against each other, damaging the joint capsule and the surrounding ligaments. The result is pain, swelling, and bruising at the knuckle as well as difficulty in bending the joint, though these symptoms usually diminish within weeks with the application of the RICE method — rest, icing, compression, and elevation.
Each finger is made up of two interphalangeal joints, or joints between the three phalanx bones of the fingers, while the thumb has only one. A jammed finger can also be sustained at the metacarpophalangeal joint, which is the large knuckle where the phalanx bone meets the metacarpal bone of the hand. All are synovial or moveable joints, which feature a membrane-enclosed joint capsule between the two bones. Within this capsule are cartilaginous disks that cushion the bones against one another, as well as synovial fluid to lubricate the joint against bone-on-bone friction. When a finger is jammed, the joint capsule is severely compressed, which damages and inflames the tissues within.
To either side and on the palm side of each joint are ligaments holding the bones together. Those running between the bones on either side are known as collateral ligaments, while the thick ligament linking the bones on the palm side of the hand is known as the volar ligament. When one sustains a jammed finger, these ligaments are sprained, which occurs much like a whiplash injury in which a rear-ended driver’s head is thrown forward and then back. Quickly compressed and then hyperextended, the ligaments become painfully inflamed. Swelling and bruising may occur as fluid and blood rush to the joint to protect and heal the injury.
After sustaining a jammed finger, immediate treatment is recommended. Ice should be applied to the injury site, and NSAID pain relievers may be taken, both of which will address the inflammatory pain and swelling. The joint should be rested and in more severe cases immobilized with a splint. If the injury is minor, it is recommended to try gently moving the joint within a few days. If it appears severe, however, it may be advisable to obtain an X-ray to determine whether a fracture has occurred.