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Bones & Joints
Patellofemoral instability is a condition where the kneecap (patella) is prone to slipping out of place (dislocating) to the outside of the knee, most commonly affecting adolescents and young adults (particularly teenage females) during pivoting or cutting activities. The first dislocation typically occurs during sports (netball, basketball, football, dance) when changing direction suddenly, causing immediate severe pain, visible deformity (kneecap displaced to outside of knee), and inability to straighten the leg—though kneecap usually reduces spontaneously or with gentle straightening. Patellofemoral instability results from combination of anatomical risk factors (shallow trochlear groove—shallow femoral groove kneecap sits in, high-riding kneecap—patella alta, increased Q-angle causing lateral pull, ligamentous laxity) and soft tissue injury to the medial patellofemoral ligament (MPFL—main restraint preventing lateral dislocation) which tears during dislocation. After first-time dislocation, recurrence risk is 15-44% overall but up to 60% in high-risk patients with anatomical abnormalities. Treatment after first dislocation: conservative management (immobilization 2-4 weeks, physiotherapy for quadriceps strengthening and VMO retraining) appropriate for 60-70% who don't have recurrent instability, versus surgical stabilization (MPFL reconstruction, tibial tubercle osteotomy, trochleoplasty) reserved for recurrent dislocators or those with major anatomical risk factors. Surgical outcomes: 85-90% success preventing recurrent dislocation after MPFL reconstruction in appropriately selected patients.
What it is and why it happens
Patellofemoral instability is a condition where the kneecap (patella) is prone to slipping out of place (dislocating) to the outside of the knee, most commonly affecting adolescents and young adults (particularly teenage females) during pivoting or cutting activities. The first dislocation typically occurs during sports (netball, basketball, football, dance) when changing direction suddenly, causing immediate severe pain, visible deformity (kneecap displaced to outside of knee), and inability to straighten the leg—though kneecap usually reduces spontaneously or with gentle straightening. Patellofemoral instability results from combination of anatomical risk factors (shallow trochlear groove—shallow femoral groove kneecap sits in, high-riding kneecap—patella alta, increased Q-angle causing lateral pull, ligamentous laxity) and soft tissue injury to the medial patellofemoral ligament (MPFL—main restraint preventing lateral dislocation) which tears during dislocation. After first-time dislocation, recurrence risk is 15-44% overall but up to 60% in high-risk patients with anatomical abnormalities. Treatment after first dislocation: conservative management (immobilization 2-4 weeks, physiotherapy for quadriceps strengthening and VMO retraining) appropriate for 60-70% who don't have recurrent instability, versus surgical stabilization (MPFL reconstruction, tibial tubercle osteotomy, trochleoplasty) reserved for recurrent dislocators or those with major anatomical risk factors. Surgical outcomes: 85-90% success preventing recurrent dislocation after MPFL reconstruction in appropriately selected patients.