Patella instability is a frequent cause of knee pain in adolescents and young adults. The patella is often called the “knee cap”.
The patella connects the thigh muscles (quadriceps) to the tibia (shin bone). The patella normally sits in a groove in the lower end of the femur called the femoral trochlea. If this groove is too shallow or if trauma or sporting accidents occur, the patella can dislocate.
Patella instability is more common in females than in males.
Damage to the lining of the patella or the trochlea can occur with patella dislocations.
Symptoms of patella instability include swelling, buckling of the knee, pain at the front of the knee and cracking sounds or crunching sensations during movement of the knee.
The diagnosis of patella instability is made by taking a thorough history and performing a physical examination. X-rays of the knee are useful to assess the position of the patella and the size and shape of the femoral trochlea. CT and MRI scans provide further information including identifying any damage to the articular surface and more information about the shape of the femoral trochlea.
Treatment of patella instability
If an acute patella dislocation occurs, it will often spontaneously reduce itself. If this does not occur an urgent reduction of the patella is required. This can be done on the sporting field but sometimes needs to be done under sedation in the emergency department of a hospital.
Physiotherapy is very important for any patient with patella instability. By increasing the strength of the quadriceps muscles, patella instability can sometimes resolve or at least decrease. Braces can be useful and cycling and gym exercises can also aid in the management of this condition.
If patella instability continues to occur despite non-operative treatment, then surgery may need to be performed. Surgery for patella instability is generally very successful. It can involve soft tissue procedures to tighten the medial (inner) supports of the patella. It can also involve bony procedures to realign the tracking of the patella.