Patellofemoral Pain Syndrome (PFPS) umbrellas all pain-causing conditions arising from the patellofemoral joint or its surrounding soft tissues.

The syndrome is a chronic condition of the knee that worsens with time-limiting movements like squatting, sitting, climbing stairs, and running.

Often referred to as anterior knee pain, the pain can originate from anywhere in the knee, including the popliteal fossa at the back of the knee.

The condition is also called runner's knee, as it is more common in people who participate in sports that involve running and jumping.

The pain of patellofemoral syndrome aggravates walking, climbing stairs, extended sitting, or squatting.  Conservative treatment alongside physical therapy helps manage the condition.

Clinical anatomy

The knee comprises of two significant joints;

• the tibiofemoral joint
• the patellofemoral joint

The patella is accommodated within the femoral groove. Its posterior side is cushioned by cartilage that glides over the cartilage of the anterior part of the femur, the femoral condyles.

The patellofemoral joint is a synovial joint and is filled with fluid that facilitates smooth gliding motion of the patella over the femur. Several bursae are also present in the knee joint, the capsule of which embraces patella all around.

The collateral ligaments of the knee joint are merged with the capsule, thereby bolstering the joint stability.  There is a bursa present anteriorly between the patellar tendon (on the patella) and the skin.

The other two bursas present are prepatellar and infrapatellar that allows for smooth movements at the knee joint.  Bursitis of these bursas also contributes to knee pain around the patella.

The two ligaments of the knee linked to patellofemoral syndrome include collateral ligaments, lateral and medial. These are merged with the capsule of the knee joint.

Epicondylopatellar and meniscopatellar ligaments form the medial and lateral retinaculum ligaments of the patella. They provide for a medial and lateral attachment of the patellar tendon at the level of the patella.

Causes of patellofemoral syndrome

Patellofemoral syndrome is associated with;

• Overuse of the knee joint puts stress on joint elements resulting in irritation under the kneecap.
• Hip Muscle imbalances or weaknesses destabilizes the kneecap causing pain on squatting.
• Injury and trauma to the kneecap (dislocation or fracture) result in the patellofemoral pain syndrome.
• Surgery on the knee joint (particularly repair of the anterior cruciate ligament) increases the risk of patellofemoral pain.

Some predisposing risk factors of the patellofemoral joint include:

• Age; adolescents and young adults are more at risk of patellofemoral syndrome
• Gender and anatomical variations; women are more likely to get knee pain due to the subject syndrome because a wide pelvis increases the angle of the bones meeting in the knee joint.
• Sports activities involving running and jumping put extra stress on your knees, especially when training intensity increases.
• Knee hyperextension, lateral tibial torsion, tightness in the iliotibial band, hamstrings, or gastrocnemius muscles may also cause the patellofemoral syndrome.
• Patellar disorientation and malalignment cause the patella to glide more to one side of the femur resulting in an imbalance of load and increased pressure. It results in pain, discomfort, or irritation.

 Certain factors can provoke such deviations;

• Patellar orientation may vary in one leg from the other in the same patient. This could be anatomical in origin. Such deviations result in muscle imbalance around the knee joint and biomechanical abnormalities. This may be an instigating factor of patellofemoral syndrome.
• Muscular imbalances result in patellar deviation. In the case of a weak Vastus Medialis, the Vastus Lateralis exerts a higher force resulting in a glide, tilt, or rotation of the patella in the lateral direction. The resultant overuse of the lateral side of the femur results in pain or discomfort.

               Medial tilt is a rarity.

• Imbalance or weakness of the iliotibial band or the lateral retinaculum also causes patellar disorientation and patellar syndrome.
• Sometimes a localized pain in the knee is present, but the source of the pain does not lie in the joint. Pronation or supination of the foot can provoke PFPS.

             More often, a compensatory internal rotation of the tibia or femur may occur due to pronation. It upsets the patellofemoral mechanism. Similarly, foot supination also causes a less cushioning effect when striking the ground resulting in stress on the patella.

• Weak hip abductor muscles associated with an increase in hip adduction during running can also trigger patellofemoral pain syndrome.

Symptoms of patellofemoral syndrome

Patellofemoral pain syndrome is marked by a dull, aching pain in the front of your knee.

Some aggravating factors for this anterior knee pain include;

• Climbing stairs
• Kneeling or squatting positions
• Sitting with a bent knee for an extended period
• cracking or popping sounds in the knee on activity or after sitting for an extended time

There is no locking of the knee joint in PFPS.

Diagnosis of patellofemoral pain syndrome

History of presenting complaints and physical examination gives a clue to the condition.

The pain of the PFPS is usually;

• Insidious in nature
• Not linked to trauma or injury
• Associated with overloading of the knee joint as long-distance running and excessive stair climbing

Anterior knee pain with activities like climbing stairs, sitting with knees flexed, squatting, kneeling, or returning from squat are all indicative of PFPS.

X-rays, CT scans, and MRI confirmed the diagnosis of PFPS.

Treatment

Conservative treatment, including changes to training regimen and self-care, reduces the symptoms of patellofemoral pain syndrome.  

Patients with pain affecting both knees and the elderly may require more prolonged duration treatment. Similarly, the underlying cause also affects the outcome of the condition. For example, in cases of dislocation of the kneecap, the PFPS may take as long as five to six months to recover and heal.

1. Conservative treatment during the early days

1. RICER
2. Medications
3. TENS
4. Surgery

Arthroscopic surgery to remove the fragments of any damaged cartilage can be taken up. In more severe cases, open surgery to re-align the kneecap or relieve the cartilage pressure may be done.

• After the pain has resolved or subsided

• Massage
• Therapeutic ultrasound
• Active rehabilitation

Physical rehabilitation after pain has reduced in intensity should be initiated.  Such exercises stretch and strengthen the muscles associated with the knee joint.

Isometric exercises which are performed with the knee fully extended can be initiated early in therapy. These help to minimize stress on the patellofemoral joint while reinforcing the quadriceps at the same time. Pillow squeeze and straight leg raises are some of the isometric exercises.

Closed kinetic chain exercises put less stress on the patellofemoral joint. They should be done within pain-free limits. For example, squats.

Strengthening exercises of the hip abductors and lateral rotators benefit PFPS. Eccentric hip abduction strengthening exercises improve the condition in such patients.   

Leg extensions

This exercise strengthens the quadriceps muscles on the front of the upper thigh.

• Sit in a chair and place both feet flat on the ground in a comfortable position.
• Raise your right leg and straighten it to extend it. A stretch is felt in the muscles of the upper thigh, the quads.
• Hold the position for few seconds.
• Lower the leg and place your foot on the ground.
• Repeat with the other leg.
• Perform two sets each of twelve reps on each side.
• Make sure to take a break between the sets or whenever the pain is intense.

Quadriceps stretch

After leg stretch, the quads stretch helps to stretch the muscles of the thigh that underwent extension.

• Stand and take support with your left hand from a chair or a sturdy table.
• Keep your left leg straight but with a bit of bend at the knee to avoid overload.
• Flex and pull your right foot toward your buttocks.
• Grasp the top of your right foot with your right hand gently.
• Apply gentle pressure and pull the right knee towards the floor.
• You should feel a stretch in the front of your thigh.
• Hold this stretch for half a minute.
• Release the leg slowly. Rest for few seconds and repeat with the other leg.
• Perform five reps on each side.

Prevention

• Maintain strength by working on the quadriceps and hip abductor muscles. It helps to maintain a balanced knee during physical activity.
• Avoid deep squatting during your weight training to safeguard against pain.
• Take care of alignment and technique while jumping, running, and pivoting. Regularly uptake flexibility and strength exercises even in the off-season.
• Lose weight if obese to relieve pressure off the knee joint.
• Warm-up before running or other sports.
• Stretch after exercise.  
• Increase training intensity gradually.
• Wear appropriate gear for your sports.
• Use shoe inserts if flat-footed.
• Get a regular sports massage to relax muscles that may trigger PFPS.
• Alternate between different activities to avoid overuse. Switch from high-impact exercise to low-impact workout during the week.