You may have a central slip injury if the middle knuckle of your finger looks bent. A central slip injury occurs when an important ligament on the back of the finger is broken, making it difficult to fully straighten the finger. This important tendon is called the ‘central slip’. Sometimes it’s just sore around the back of the knuckle and then, over the next few days to weeks, it becomes more and more difficult to straighten the finger.

Tell me more about central slip injury.

If you have a central slip injury, the joint will be swollen, sore and tender across the back. The X-ray will be clear, but this doesn’t mean that nothing is wrong, as X-rays will not show up a soft tissue injury like a central slip.

It is important to get the right treatment for a central slip injury, as it progressively worsens when left untreated and becomes what is called a ‘boutonnière’ (or button-hole deformity). As the middle joint bends further down, the fingertip bends gradually further back until the finger is quite crooked. 


What causes a central slip injury?

Central slip injuries are caused when the middle knuckle of the finger (proximal interphalangeal joint) is forcibly bent forwards. This often happens when the finger punches something, is hit by a ball or is knocked forcefully. The joint may pop out of place but doesn’t normally stay dislocated or look out of place later on. It commonly occurs amongst people who have rheumatoid arthritis without trauma. A cut to the back of the finger joint area can cause a central slip injury if it goes all the way through the tendon.


How do I know if I have a central slip injury to my finger?

Following a bad knock to the finger, the finger will be sore and swollen and you will notice that it is difficult to straighten the middle joint. This may not be obvious or noticeable at the time of the injury, and often gradually gets worse in the following days and weeks. The sorest spot to touch will be right on the back of the middle joint. The fingertip may start to bend backwards, and the X-ray will be normal.


How can physiotherapy help with central slip injuries?

The central slip needs to be splinted with the joint held out completely straight to heal properly. It will need a splint to hold it in that position constantly for up to six weeks. If the finger has already become stiff and you’re unable to straighten the finger fully with the other hand because the injury is a few days’ or weeks’ old, you will need two splints—one to straighten the finger and then a second splint to hold it straight for the six weeks.

Once the tendon is healed, the joint will be stiff and need to be stretched. Your physiotherapist will assess how much support and exercise is needed for healing. At this point, you can do strengthening and mobility exercises to restore normal movement and function.

It’s important to note that not all physiotherapists are specialised in the area of hand therapy. For the best treatment outcome, find a physio who specialises in this area.


How effective is physiotherapy for central slip injuries?

Most central slip injuries do not need an operation to fix them—a splint and graduated exercises are all that is needed to return the finger to normal or near-normal functioning. The best results are achieved when a well-fitting splint is applied straightaway by a physiotherapist experienced in finger injuries and custom-made splinting. Occasionally, surgery is required to fix these central slip injuries, and this is more often the case when a delay in treatment occurs. If the central slip injury is caused by a cut, surgery is usually required to repair the tendon.


What can I do at home?

The injury initially needs to be supported straight by a splint at all times. Central slip injuries often need to avoid any bending while the tendon heals. Appropriate splinting or taping as guided by your physiotherapist will ensure that you achieve a good result. At an appropriate time, regular exercises and return to activity and sport are essential to regain movement and strength.


How long until I feel better?

Pain should resolve as soon as the finger is appropriately splinted. You will be able to do most of your everyday activities while you are wearing the splint. Mild central slip tears recover within weeks of treatment. More severe injuries take up to six weeks of constant splinting and may take 2–3 months to achieve 80­–90 per cent strength. The final discomforts and weaknesses may take longer to resolve, but rarely reduce function in the meantime.