Unstable kneecap, also known as patellar instability or patellar subluxation, occurs when the kneecap is displaced from its normal alignment within the femoral groove.
The symptoms of an unstable kneecap include pain, often at the front of the knee, swelling, bruising and visible deformity.
Functionally, instability can inhibit joint range of motion and an inability to bear weight on the affected limb. Any movement of the joint may be accompanied by a clicking or grinding sound (crepitus) as the kneecap moves in and out of the femoral groove.
As with other injuries of the knee joint, instability can result from direct impact or from the stresses associated with acute twisting or pivoting movements. Repeated stress on the knee joint, of the type associated with running and cycling, can also contribute to instability over time.
There are a larger number of factors which can contribute to an increased likelihood of instability, including the presence of lax or damaged ligaments, knock knees, flat feet or arthritis of the knee joint.
Non-surgical treatment options are designed to manage pain and improve stability of the knee, thereby reducing the risk of future injury. They include:
Physical therapy: particularly including exercises targeting the quadriceps to preserve alignment of the knee joint, and stretching of the Iliotibial band which can reduce lateral pull on the kneecap.
Bracing or taping: bracing can be used to hold the kneecap in proper alignment during movement. Kinesiology taping can also be used to offer a less rigid form of support.
Orthotics: can be used to correct flat feet or similar structural or gait issues which may increase the risk of instability.
Surgical treatments for an unstable kneecap include:
Lateral release: involves release (cutting) of the lateral retinaculum on the outer side of the knee to enable realignment of the knee.
Medial Patellofemoral Ligament (MPFL) reconstruction: the MPFL can be reconstructed using a graft to stablise the kneecap and reduce the risk of future instability.
Tibial tubercle osteotomy: used when the kneecap is misaligned as a result of the abnormal position of the tibial tubercle.
Trochleoplasty: involves the reshaping and deepening of the trochlear groove of the femur to better hold the kneecap in place.
Arthroscopy: a minimally-invasive procedure designed to provide direct access to the knee joint, allowing for soft tissue or ligamentous repair, and the removal of debris. To learn about knee arthroscopy and what to expect from the procedure, visit our knee arthroscopy page.
For further inquiries or to arrange a consultation, please contact Professor Al Muderis’ office at +61 2 88829011 or book an appointment online.
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Professor Dr Munjed Al Muderis is an orthopaedic surgeon specialising in osseointegration, hip, knee and trauma surgery. He is a clinical professor at Macquarie University and The Australian School Of Advanced Medicine, a fellow of the Royal Australasian College of Surgeons and Chairman of the Osseointegration Group.