FAQs Patellofemoral (kneecap) instability and dislocation
What is the patella (knee cap)?
The kneecap is the structure at the front of the knee it helps transmit the pull of the quadriceps so that the knee can straighten fully and take the weight of the body when walking or running.
Where in the knee is the patella/kneecap?
The kneecap sits in front of the thighbone, making a joint known as the patellofemoral joint.
Classically, the kneecap sits in a groove on the thighbone known as the trochlea groove, which is a little bit like a train running on its tracks.
How does the kneecap move when the knee bends and straightens?
When the knee bends and straighten the kneecap stays in a straight line.
What is a patella dislocation?
The kneecap can move out of its position almost always towards the outside of the knee, or laterally.
This can happen because of a nasty injury. In some patients it can happen because their anatomy predisposes to kneecap dislocation.
What structures are damaged when the kneecap dislocates?
A ligament on the inner (the medial) aspect of the kneecap known as the medial patellofemoral ligament is most often ripped after a dislocation.
Sometimes during the dislocation, the kneecap bone can strike the thighbone and cause bruising of these bones or a chip on the bone known as a fracture or osteochondral injury.
Sometimes the kneecap stays out of position and requires to be put back by a medical professional or, by the patient themselves.
What are the symptoms of patella instability?
The feeling of the kneecap moving out of position.
The knee feeling unstable especially when twisting or kneeling.
Pain around the front of the knee related to the instability or bone bruising particularly when going up and down stairs or kneeling.
Which structures stop the kneecap from dislocating?
The medial patellofemoral ligament, acts like the reins of a horse which prevents the kneecap from dislocating laterally
The inner quadriceps muscle, known as vastus medialis obliqus, or VMO.
The contour of the grooved the kneecap sits in (train tracks) known as the trochlea groove: the deeper and more symmetrical to groove the more stable the kneecap. The shallower or flatter the groove, the more unstable the kneecap
The pull of the quadriceps and patella tendon: if this is in a straight line the kneecap is more stable. If the pool is more at an angle, the kneecap is more unstable.
How do we determine if these factors Arm healthy all abnormal in a particular patient?
Mr Gupte will examine your knee thoroughly to assess for anatomy of the knee, and whether the medial patellofemoral ligament is intact or not.
Once the examination is done, it is likely that MRI, plain x-rays, and sometimes a CT scan can help determine the architecture of your bones as well as the competence of the medial patellofemoral ligament and the surfaces of the bones.
How do we treat patellofemoral instability?
Treatment consists of:
physiotherapy to strengthen buttock and quadriceps muscles,
Orthotics to help correct the alignment of the knee
Sometimes braces can help patella prevent patella dislocation in recurrent dislocators.
When is surgery required?
Surgery is most often required for people who keep suffering from recurrent patella dislocation which affects their life.
Surgery may also be required when a patella dislocation occurs for the first time with a fracture of the kneecap or the surface of the bone, known as an osteochondral fracture.
What are the different surgical options?
A thorough clinical examination and investigation profile will help determine which of the following options are appropriate in any one person:
Medial patellofemoral ligament reconstruction
Patella realignment surgery with tibial tubercle transfer
Deepening the groove, known as trochleoplasty
Is surgery successful?
Previous studies show and 90 to 95% success rate of patella stability after surgery. Some residual side effects can include discomfort around the kneecap but most patients experience an improvement in this pain and function.
What is the rehabilitation like after surgery on the patella?
Each rehabilitation regime is tailored towards The individual patient and the particular operation that has been performed.
However, in general the rehabilitation involves:
A period of 6 to 8 weeks in a brace.
A period of 4 to 8 weeks on crutches.
Initially, the knee is held in a reasonably straight position with a gradual increase in bend over time.
The initial swelling is managed with ice.
There is a 6 to 9 months rehabilitation period to get the knee and leg back to strength and full function.