What a jammed finger is
"Jammed finger" isn't a diagnosis: a sports review calls jam injuries a host of injuries that can be hard to tell apart. Most are sprains of the middle joint of the finger (the proximal interphalangeal or PIP joint), the most commonly injured joint in the hand. The usual structure hurt is the volar plate, a thick, strong ligament on the palm side of the joint that stops it bending backwards. It can be stretched or torn, or pull a small flake of bone off the base of the middle bone (an avulsion fracture).
The ligaments on each side of the joint can be sprained too, when the finger is bent sideways. The volar plate also tears when the joint dislocates, so a jammed finger and a dislocated one are the same injury at different strengths; a finger that came out of joint has its own guide.
Sources 1, 2, 3, 4, 5, 6
Who gets it
Usually a ball hits the end of a straight finger and forces the middle joint backwards: basketball, netball, cricket, goalkeeping and other ball sports. Falls onto the hand, and catching the finger on a door handle or furniture, do it too. It hurts at the time, although one NHS leaflet notes it's often possible to finish the game.
Fingers are the part of the arm most often injured in US emergency departments: 38.4% of an estimated 3.5 million arm and hand injuries in 2009. In the Netherlands, about 10,000 people a year dislocate the middle joint or bend it backwards hard enough to pull off a flake of bone, and in a Dutch trial of 200 of them, about half the injuries happened in sport.
Sources 3, 6, 7, 8, 9, 10
How it's recognised, where to go, and what an X-ray changes
Pain on the palm side of the middle joint, swelling and bruising (often on the palm side), stiffness, difficulty bending or fully straightening the finger, and pain when you grip. The NHS says it can be hard to tell whether a finger is broken, dislocated or badly sprained, and you'll probably need an X-ray.
Where to go: a finger that is out of shape, crooked or pointing at an odd angle may be broken or dislocated, so go to an urgent treatment centre or A&E. A finger that is the right shape but painful, swollen and bruised, or that you can't move or bend properly, starts with NHS 111, which will tell you where to go. Numbness, a blue, white or cold finger, or bone showing means 999 or A&E.
What the X-ray changes: no break, or a small flake of bone with the joint lined up, gets the same treatment, buddy strapping and early movement. In 190 people with these flakes, their size and how far they had moved didn't affect the outcome, and in 75 people with stable sprains, results were the same with or without one. A large fragment (about 40% of the joint surface or more, or 30% in children's studies), or a joint that won't stay lined up, needs a hand specialist and often surgery. Some stable injuries with a bigger fragment are splinted slightly bent for 3 to 6 weeks.
Sources 1, 3, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18
Injuries that can look like a jammed finger
Some injuries that start as a "jammed finger" are something else, and each has its own guide. A torn tendon on the back of the middle joint (a boutonnière injury) can look like a sprain for days or weeks but needs a different splint. A fingertip that won't bend after a grab (jersey finger) is often first taken for a sprain. A fingertip that droops and won't straighten is mallet finger. And a break can twist the finger, so that it crosses its neighbour when you make a fist (the broken finger guide).
Sources 11, 19, 20
How long it takes
Most jammed fingers heal without surgery and get back to good use over a few months, but it takes longer than people expect. The British Society for Surgery of the Hand (BSSH) says some mild swelling and pain may last into the longer term, and the finger can be sensitive to touch or cold for 1 or 2 years. NHS leaflets say the swelling can take up to 6 months to settle, the joint may stay thicker for 12 to 18 months or for good (which doesn't usually affect how it works), and you shouldn't have rings resized for at least a year. The commonest lasting problem is losing a little straightening, which usually doesn't affect function.
In a Dutch trial of 200 adults with a dislocated middle joint or a volar plate injury with a flake of bone, hand function scores rose from about 68 out of 100 at the start to about 92 at 3 months, finger movement was 91% of the other side at 6 weeks and 95% at 3 months, and 7 to 9% still reported stiffness at 3 months. In 67 people with sprains of the side ligaments treated with buddy strapping, grip was 77% and movement 84% of the other side at 6 months, and starting treatment later went with less movement.
Coming late doesn't rule out a good result: 14 people first seen about a month after the injury gained about 25 degrees of movement with a hand therapist, and all got back to their previous level of function.
Sources 3, 4, 5, 7, 8, 10, 21, 22, 23
Children
Volar plate injuries are common in children, usually from a ball. One NHS children's service says they generally heal by themselves in about 6 weeks, with buddy strapping day and night for about 2 to 3 weeks and stiffness for up to 6 weeks. A review of 25 studies (268 children) found good results without surgery when less than 30% of the joint was involved. In a small observational study of 20 children, going straight to buddy taping gave more movement and less pain at 1 to 2 weeks than a week in a splint first, with no difference by 4 weeks, and in a trial of buddy strapping, children did better than adults.
Sources 17, 24, 25, 26