This is the first of a three-part series on a condition called patellofemoral pain syndrome (PFPS). The focus of this article is on classifying the problem according to the biomechanics and treating it according to whether there is pain or instability.
The patellofemoral joint is the located where the patella (knee cap) meets the end of the femur (thigh bone). Patellofemoral pain syndrome causes pain under and/or around the kneecap. When there is instability, the patella slips and slides during movement. Dislocation of the patella is a common feature of instability-related PFPS.
The authors carefully explain the biomechanics of the normal knee. Understanding the way the structures of the patellofemoral joint move and function is important when treating this condition. The physical therapist must strengthen the correct muscles to balance the forces around the joint. Too much pull in one direction can cause additional problems.
The main symptoms of PFPS are pain along the sides of the patella. The pain may travel to the back of the knee. Load on the patellofemoral joint and the joint’s response to that load vary from patient to patient. That’s why each patient has his or her own unique rehab program for this problem.
For patients who feel like the kneecap is loose or slipping, there may be an actual patellar subluxation (partial dislocation) or full dislocation. Every time the patella dislocates, there is pain but also inflammation. Patellar dislocation is often the cause of cartilage tears and patellar bone fractures.
Once the patella has dislocated, recurrent dislocations are common. After the second dislocation, the other knee is at increased risk of a first dislocation. Some people are more susceptible to patellofemoral joint dislocations than others.
Risk factors include family history of patellofemoral dislocations and a personal history of developmental dysplasia of the hip. Women are more likely to have more than one dislocation. Shortened and tight or loose and lax ligaments can also create patellofemoral problems.
The next part of this series will present the examination of the patellofemoral joint. That will be followed by a third part discussing various ways to treat this problem.