Overview of Patellar Dislocation

Patellar dislocation occurs when the kneecap (patella) is forced out of its normal position within the groove of the femur (thigh bone). This injury is usually caused by a hard impact or fall but can sometimes be due to structural issues within the knee. It can be very painful and can lead to further complications if not managed properly. It is vital that even if the kneecap slips back into place on its own, you should seek professional advice from a knee specialist to help you manage your symptoms, and to get a full examination of your knee to identify the cause, and any damage to the knee joint and surrounding soft tissues. If you have dislocated your knee cap once it is more likely to dislocate in the future, so getting the most appropriate treatment as soon as possible is important.

The patella sits in the front of the knee joint and moves within the trochlear groove (a small channel) of the femur (thigh bone) when the knee is bent or extended. Ligaments, tendons, and muscles help stabilise and guide the patella’s movement.

Causes of Patellar Dislocation

Patellar dislocation can result from various factors:

Direct Trauma 

A blow to the knee, especially while the leg is slightly bent, can force the patella out of its groove. It can also occur as a result of a sudden change of direction while the leg is still planted firmly on the ground, such as during sports or dancing.

Muscle Imbalances:

Weakness or imbalances in the quadriceps muscles (4 thigh muscles) can affect the patella’s alignment.

Anatomical Factors:

Some individuals have a shallow trochlear groove, making patellar dislocations more likely. Or some people can have very lax ligaments, making their joints extremely flexible and more prone to patellar dislocation.

Other risk factors can include:

• Being tall and/or being overweight increases the risk of dislocation.
• Women are more at risk of dislocation due to anatomical/muscular abnormalities.
• Men are more likely to sustain a traumatic dislocation from a direct injury.

After a dislocated kneecap, the knee ligaments that secure the kneecap in place may be damaged or completely torn. This can lead to recurrent dislocation of the kneecap.

Symptoms of Patellar Dislocation

Symptoms of a patellar dislocation can include:

• Sudden Pain: Immediate, sharp pain in the knee at the time of dislocation.
• Swelling: Swelling around the knee due to tissue irritation.
• Reduced Movement: Inability to bend or straighten the knee
• Visible Deformity: The patella may appear displaced, creating an abnormal appearance of the knee.
• Audible Pop: People often report hearing a pop at the point of injury
• Inability to Weight Bear: Patients may not be able to walk or put any weight on the injured leg.

Diagnosis of Patellar Dislocation

Diagnosing a patellar dislocation typically involves:

• Physical Examination: Your knee specialist will carry out a thorough clinical assessment, looking at knee alignment, stability, and areas of tenderness.
• Imaging Tests: X-rays will be done to rule out fractures and, in some cases, MRI scans to evaluate soft tissue damage.

Treatment Options of Patellar Dislocation

It is important to get treatment for a patella dislocation immediately. If it doesn’t go back into place on its own, then you will need to go to an urgent treatment centre or A&E. Once it is back in place you will still need ongoing treatment to help with symptoms and prevent recurrence.

• Closed Reduction: A healthcare provider gently manoeuvres the patella back into its groove.
• Immobilisation: You will normally need crutches and/or a knee brace to immobilise the knee while your knee is healing.
• Physiotherapy: Rehabilitation is a vital part of your treatment. You will need to start a Physio led exercise programme to strengthen all your lower leg muscles, especially the quadriceps, stabilise the kneecap, and improve knee biomechanics.

Surgical Options for Patellar Dislocation

Surgery is considered if there are recurrent dislocations, significant ligament damage, and if conservative management has not been effective.

Medial Patellofemoral Ligament (MPFL) Reconstruction: Rebuilding the ligament to stabilise the patella’s movement.

Common Questions and Answers

Can a patellar dislocation cause long-term knee problems?
Without proper treatment and rehabilitation, recurrent dislocations can lead to chronic instability and cartilage damage.

Can I resume sports after a patellar dislocation?
Depending on the severity of the injury, proper rehabilitation, and consultation with a healthcare provider, you may be able to return to sports after recovery.

Can patellar dislocations be prevented?
Strengthening the quadriceps, practising proper techniques, and ensuring your knee is as stable as possible, can reduce the risk of patellar dislocations, especially in sports.

How long does it take to recover from a patellar dislocation?
Recovery time varies based on the severity of the dislocation and the chosen treatment. Mild cases may recover within a few weeks, while more complex cases may take several months.

Will surgery guarantee no further dislocations?
While surgery can significantly improve stability and reduce the risk of further dislocations, it’s essential to follow post-operative rehabilitation guidelines for optimal outcomes.