The kneecap (patella) is a small bone in the front of the knee that helps support the extensor mechanism (quadriceps and patellar tendon) that allows people to straighten the knee. As the knee bends, the patella glides along a groove on the femur bone – the trochlea. Patellar instability refers to a condition in which the patella slides out of the trochlea (dislocates). When the patella dislocates, a strong ligament on the inside of the knee (the medial patello-femoral ligament – MPFL) tears completely. Although the MPFL can partially heal without surgery, patients who sustain a patella dislocation are at risk of dislocating the patella in the future. Other injuries that may occur when the patella dislocates include a cartilage injury to the patella or trochlea or a meniscal injury.
There are several factors that are risk-factors for developing patellar instability. One factor is patellar tracking. In some individuals, the patella tracks on the outside of the trochlea instead of in the middle. These individuals may have a high “Q angle,” which indicates that the patellar tendon pulls the patella bone to the outside of the knee. Some individuals also have a shallow trochlear groove (a flat trochlea). When the trochlea groove is shallow or flat, the patella is unstable as the knee bends and can slip out of place (dislocate). Other individuals have very loose ligaments (ligamentous laxity) and are also at risk for developing patellar instability.
- Severe pain in the knee during a dislocation
- Sense of kneecap slipping or moving out of place
- Pain in the front of the knee when squatting, lunging, or with stairs
Diagnosis And Treatment
Dr. Keller considers each patient’s symptoms, as well as a detailed physical examination, x-rays, and sometimes an MRI of the knee to make the diagnosis. Dr. Keller recommends non-surgical management for most patients with patellar instability. A dedicated physical therapy program is a very important part of the treatment plan. Physical therapy focuses on strengthening of the core muscles, hip muscles, as well as the quadriceps. A properly executed physical therapy program can help stabilize the patella. Other non-surgical options for treatment include stabilizing braces, such as hinged brace with a cutout for the patella, oral anti-inflammatory medication, as well as injections, including steroid injections. In those patients who do not improve with non-surgical management, Dr. Keller may recommend surgical intervention of the cartilage lesion AND/OR a soft tissue procedure.