The kneecap (patella) attaches the large powerful thigh muscles (quadriceps) to the upper part of the shin bone (tibia). The patella sits in a groove on the front of the thigh bone known as the trochlea, and tracks up and down as the knee bends and straightens.
Poor kneecap tracking, or poor muscular control are a cause of knee pain and episodes of giving way. In more extreme circumstances, the kneecap can dislocate (come out of joint), which almost always happens towards the outer aspect of the knee.
When a patella fully dislocates the normal ‘restraining’ structures (ligaments) on the inner aspect of the patella are stretched or torn, making it more likely that similar episodes will recur.
Unless the initial dislocation causes a fracture or significant cartilage damage, an urgent operation is not needed. A trip to the Emergency Department may be needed to get the kneecap back into its groove, and the knee may be temporarily placed into a brace or a splint. Early physiotherapy is then crucial to regain range of movement and muscle function, and to work to reduce the chance of repeat episodes. Patella taping or strapping can help.
If a ‘non operative’ approach has failed then an operation may be recommended. The particular operation will depend on the underlying anatomy and integrity of the ligaments which will usually need an MRI scan to check.