Patellofemoral pain syndrome
|Patellofemoral pain syndrome|
|Classification and external resources|
Patellofemoral pain syndrome (PFPS) is a syndrome characterized by pain or discomfort seemingly originating from the contact of the posterior surface of the patella (back of the kneecap) with the femur (thigh bone). It is the most frequently encountered diagnosis in sports medicine clinics.
The cause of pain and dysfunction often results from either abnormal forces (e.g. increased pull of the lateral quadriceps retinaculum with acute or chronic lateral PF subluxation/dislocation) or prolonged repetitive compressive or shearing forces (running or jumping) on the PF joint. The result is thinning and softening (chondromalacia) of the articular cartilage under the patella and/or on the medial or lateral femoral condyles, synovial irritation and inflammation and subchondral bony changes in the distal femur or patella known as "bone bruises". Secondary causes of PF Syndrome are fractures, internal knee derangement, OA of the knee and bony tumors in or around the knee.
Specific populations at high risk of primary Patellofemoral Syndrome include runners, bicyclists, basketball players, young athletes and females. Typically patients will complain of localized anterior knee pain which is exacerbated by sports, walking, stair climbing, or sitting for a long time, often called the "Theater Sign" or "Movie-Goers Sign." The pain from prolonged sitting is thought to occur because of the constant pull of the quadriceps muscle on the knee cap while sitting, which causes its impaction against the hard and unyielding surfaces of the bones of knee joint. Descending stairs may be worse than ascending. Unless there is an underlying pathology in the knee, swelling is usually mild to nil. Palpation, as well, is usually unremarkable.
Differential diagnosis 
Clinicians have traditionally used a variety of treatments for patellofemoral pain syndrome, many of which have little supporting evidence. Most patients with patellofemoral pain syndrome respond well to conservative therapy.
A 2011 systematic review stated that evidence supports the use of quadriceps exercise for managing patellofemoral pain syndrome and that quadriceps strengthening is considered to be the "gold" standard treatment for patellofemoral pain syndrome. Quadriceps strengthening is commonly suggested because the quadriceps muscles help to stabilize the patella. Quadriceps weakness and quadriceps muscle imbalance may contribute to abnormal patellar tracking. Moderate evidence supports the addition of hip abductor and external rotator strengthening, as well as exercises targeting hip flexion and hip extension. When executing these exercises, proper form is very important in order to ensure that the musculature is activated in such a way that will not lead to further injury. Inflexibility has often been cited as a source of patellofemoral pain syndrome. Stretching of the hip, hamstring, calf, and iliotibial band may help restore proper biomechanics.   Furthermore, the use of a foam roller may help to add flexibility and relieve pain from sore or stiff muscles in the leg.
Patellofemoral pain syndrome may also result from overuse or overload of the PF joint. For this reason, knee activity should be reduced until the pain is resolved. Those with pain originating from sitting too long should straighten the leg or walk periodically. Those who engage in high impact activity such as running should consider a nonimpact activity such as swimming or aerobics on an elliptical machine.
Ice and medication 
To reduce inflammation, ice can be applied to the PF joint after an activity. The ice should be kept in place for 10 to 15 minutes. Additionally anti-inflammatory drugs such as NSAIDs can also be taken immediately after an activity or judicious use during daily activities and for those people whose symptoms aren’t controlled with ice.
Orthosis and taping 
In addition to physical therapy, external devices such as patellofemoral knee orthosis and tape could be used to stabilize the knee. These orthoses will not correct the underlying source but may prevent further injury. For this reason, they should be used in conjunction with and not in lieu of physical therapy. The technique of McConnell taping involves pulling the patella medially with tape (medial glide). The underlying goal of taping is multifaceted and intended to correct the position of the patella, increase vastus medialis oblique activation, and stretch the tight lateral structures of the patella leading to pain reduction and facilitating strengthening exercises of the quadriceps. Studies have shown that patella taping may reduce pain and potentially increase the activity of the VMO, however the underlying mechanisms of taping are not clearly understood. Findings from some studies suggest that there is limited benefit with patella taping or bracing when compared to quadriceps exercises alone.
Arch support 
Low arches can cause overpronation or the feet to roll inward too much increasing the Q angle and genu valgus. Poor lower extremity biomechanics may cause stress on the knees and ultimately patellofemoral pain syndrome. Stability or motion control shoes are designed for people with pronation issues. Arch supports and custom orthotics may also help to improve lower extremity biomechanics.
See also 
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- Patient handout for patellofemoral pain syndrome by the American Academy of Family Physicians
- Runner's Knee Prescribe Treatments for patellofemoral syndrome on PrescribeExercise.com