Patellofemoral Pain Syndrome
Original Editor - Kristin Zumo
Topic Expert - Claire Robertson
- 1 Definition/Description
- 2 Clinically Relevant Anatomy
- 3 Epidemiology /Etiology
- 4 Characteristics/Clinical Presentation
- 5 Differential Diagnosis
- 6 Diagnostic Procedures
- 7 Outcome Measures
- 8 Examination
- 9 Medical Management
- 10 Physical Therapy Management
- 11 Resources
- 12 References
Patellofemoral Pain Syndrome (PFPS) is an umbrella term used for pain arising from the patellofemoral joint itself, or adjacent soft tissues. Historically it has been referred to as anterior knee pain but this is misleading as the pain can be felt in all aspects of the knee (including the popliteal fossa).
The differential diagnosis of PFPS include chondromalacia patellae and patellar tendinopathy. Both are not considered to be under the umbrella term of PFPS though patients will complain of similar symptoms. The pathophysiology is thought to be different and therefore there is alternative treatment.
Clinically Relevant Anatomy
The knee (art. Genus) consists of two major joints, the tibiofemoral joint and the patellofemoral joint. In this case, the problem will be localized in the patellofemoral joint:
The patella sits within the femoral groove; the fascies articularis patellae (posterior side) is covered with cartilage that glides over the cartilage of the anterior part of the femoral condyles (femoral groove). In this synovial joint movement and gliding creates minimal resistance due to the synovial fluid which is present around the knee and produced by the membrane synovialis, the internal part of the joint capsule during movement. Several bursae also produce synovial fluid within the capsule. The knee capsule is attached all around the patella, so only the fascies articularis patellae and femoralis are in contact with the synovial fluid. The collateral ligaments are merged with the capsule and they contributed in joint stability. On the anterior side of the patella between the patellar tendon (which is attached to the patella) and the skin, there is an extra bursa (prepatellaris) which is normally not in contact with the knee capsule and ensures a better gliding of the patellar tendon. There is a similar bursa (infrapatellaris) at the level of the tuberositas tibiae. When the knee is inflamed, these bursae can become hyperproductive (swollen). This is possible related to increase of anterior knee pain.
Although each ligament has its own responsibility in supporting and protecting the knee, ligaments also provide assistive support to other ligaments. But the two ligaments that are most associated with PFPS are the two collateral ligaments (lateral and medial), because they are merged with knee capsule. Epicondylopatellar and meniscopattelar ligaments form the medial and lateral retinaculum patellar part of a ligamentous complex which provides for a medial and lateral attachment of the patellar tendon at the level of the patella.
PFPS can be due to a patellar trauma, but it is more often a combination of several factors (multifactorial causes): overuse and overload of the patellofemoral joint, anatomical or biomechanical abnormalities, muscular weakness, imbalance or dysfunction. It’s more likely that PFPS is worsened and resistive to treatment because of several of these factors.
One of the main causes of PFPS is the patellar orientation and alignment. (fig.1) When the patella has a different orientation, it may glide more to one side of the facies patellaris (femur) and thus can cause overuse/overload (overpressure) on that part of the femur which can result in pain, discomfort or irritation. There are different causes that can provoke such deviations.
The patellar orientation varies from one patient to another; it can also be different from the left to right knee in the same individual and can be a result of anatomical malalignments. A little deviation of the patella can cause muscular imbalances, biomechanical abnormalities … which can possibly result in PFPS. Conversely, muscular imbalances or biomechanical abnormality can cause a patellar deviation and also provoke PFPS. For example: When the Vastus Medialis Obliquus isn’t strong enough, the Vastus Lateralis can exert a higher force and can cause a lateral glide, lateral tilt or lateral rotation of the patella which can cause an overuse of the lateral side of the facies patellaris and result in pain or discomfort. The opposite is possible but a medial glide, tilt or rotation is rare. Another muscle and ligament that can cause a patellar deviation is the iliotibial band or the lateral retinaculum in case there is an imbalance or weakness in one of these structures. (see table 1)
PFPS can also be due to knee hyperextension, lateral tibial torsion, genu valgum or varus, increased Q-angle, tightness in the iliotibial band, hamstrings or gastrocnemius.
Sometimes the pain and discomfort is localized in the knee, but the source of the problem is somewhere else. Pes planus (pronation) or Pes Cavus (supination) can provoke PFPS. Foot pronation (which is more common with PFPS) causes a compensatory internal rotation of the tibia or femur that upsets the patellofemoral mechanism. Foot supination provides less cushioning for the leg when it strikes the ground so more stress is placed on the patellofemoral mechanism. The hip kinematics can also influence the knee and provoke PFPS. A study has shown that patients with PFPS displayed weaker hip abductor muscles that were associated with an increase in hip adduction during running.
|Muscular etiologies of PFPS|
|Weakness in the quadriceps||
It may adversely affect the PF mechanism.
Strengthening is often recommended.
|Weakness in the medial quadriceps||
It allows the patella to track too far laterally.
Strengthening of the VMO is often recommended.
|Tight iliotibial band||
It places excessive lateral force on the patella and can also externally rotate the tibia, upsetting the balance of the PF mechanism.
This can lead to excessive lateral tracking of the patella.
|Tight hamstrings muscles||
It places more posterior force on the knee, causing pressure between the patella and the femur to increase.
|Weakness of tightness in the hip muscles||
Dysfunction of the hip external rotators results in compensatory foot pronation.
|Tight calf muscles||
It can lead to compensatory foot pronation and can increase the posterior force on the knee.
Patient's usually present with the complaint of anterior knee pain that is aggravated by activities that increase patellofemoral compressive forces such as: ascending/descending stairs, sitting with knees bent, kneeling, and squatting.
Different disease can provoke anterior knee pain, without being PFPS:
- Chondromalacia Patellae
- Hoffa's pad syndrome
- Iiotibial band friction syndrome
- Sinding-Larson-Johansson syndrome
- Patellar tendinitis
- Osteoarthritis in the knee
- Chondral lesions
- medial meniscus tears
- Medial overload syndrome
- Popliteal Cyst (Baker's Cyst)
- ACL (anterior cruciate ligament) tear
- PCL injury/rupture
- Referred pain from the hip joint (e.g. slipped epiphysis in adolescents, FAI in young adult, OA)
- Referred pain from lumbar spine
It is recommended that the diagnostic procedure to identify PFPS should involve first ruling out other pathologies that may cause anterior knee symptoms.  You can use the International Knee Documentation Committee (IKDC), which contains 18 items designed to measure symptoms associated with pain, stiffness, swelling, joint locking, and joint instability, whereas other items designed to measure knee function assess the ability to perform activities of daily living. 
The subjective examination is crucial in determining the root cause as well as contributing factors of PFPS.
A thorough subjective examination will allow you to streamline your physical examination and develop an appropriate management plan.
Asking specific questions around the behaviour of symptoms and history of the condition will help you to clinically reason the cause of symptoms and contributing factors.
Identification of various intrinsic and extrinsic factors that lead to PFPS will guide your treatment plan. The more factors identified in an individual has been shown to be correlated with higher levels of pain and functional impairment .
A detailed history will give you a multitude of clues into the cause and contributing factors of PFPS.
|Subjective Finding||Possible Clinical Reasoning|
|Insidious Onset||Typical of PFPS|
|Overload event eg excessive stair climbing, longer distance||Typical of PFPS|
|Traumatic incident||Unlikely to be PFPS|
Anterior knee pain going up and down stairs, pain when sitting with knees flexed and pain with squatting, kneeling or returning from squat all implicate PFPS. (5, cook)
The table below gives an overview of structures to examine depending on which subjective finding is identified
|Subjective Findings||Possible Clinical Reasoning|
|Pain when sitting with flexed knee (cinema sign)||Tight quadricep muscles ( sitting they compresses PFJ)|
|Pain while sitting with legs crossed||Tight ITB (Glut max and TFL tightness)|
|Pain walking downhill||Loads PFJ|
|Pain walking uphill||Tight Calf muscles
Impaired gluteal control
|Pain when wearing high heels||Increases load on PFJ
Increases distal instability
|Pain when going downstairs||PF Joint surface problems
Muscle length issues
Eccentric quads function
|Pain when going upstairs||Impaired gluteal control|
|Squat and kneel-
Going down into squat
In crouch position
Coming up from squat
Muscle length of quads
|Pain with tight clothing as you flex your knee
(eg skinny jeans)
|Compressive forces- PFPS|
|Pain with tight clothing touching/ rubbing skin||Possibly more of a Chronic Pain picture
with Sensitisation (Allodynia)
|Subjective Finding||Possible Clinical Reasoning|
|Pain only during activity||Think biomechanics|
|Pain only after activity especially much later or next day||Think inflammatory|
|Pain that improves with exercise||Think tendon/ muscle length|
- Due to the multifactorial etiology of PFPS there are many things to consider, but top of the pecking order would be.
- Observation-patella position, (eg tilt or lateralised), femoral position, relative muscle bulk, especially gluteals, vasti and calves. Presence of effusion and or Hoffa's fat pad oedema, foot position.
- Level of hypermobility of tibiofemoral and patellofemoral joints.
- ROM, especially loss of extension.
- Single stance-pelvic, femoral, foot control. Excessive use of VL.
- VMO-ability to fire, speed of firing, endurance capability at zero, ten, twenty and thirty degrees of knee F.
- Gluteals-firing and endurance as abductor and external rotator in different degrees of hip flexion.
- Muscle length-Modified Thomas test to assess hip flexors, quads and add in adduction for TFL. Hamstrings, gastrocnemius, soleus, gluteus maximus insertion into ITB, (adduction in hip flexion).
- Stair assessment-Eccentric break, excess use of pelvis or ankle to avoid knee flexion. Can pain be altered by correction of patella/femoral/foot position?
- Gait and or running: Observing for the presence of early heel rise, level of pelvic and femoral control, scissoring, stride length,trunk flexion.
Onward referral to orthopaedic consultant should occur in the presence of:
- History of patella dislocation.
- Direct blow to the knee and suspicion of patellar fracture or OCD, (pain and or swelling not settling).
- Repeated subluxing patella not responding to physiotherapy. (May suggest dysplastic PFJ).
Onward referral to pain specialist should be considered in the presence of:
- Central sensitisation not responding to pacing/cv exercise.
Physical Therapy Management
Common interventions for the treatment of PFPS are listed below:
- Manual Therapy
- open vs. closed chain exercises www.physio-pedia.com/index.php
- Quadriceps strengthening
- Patellar Taping
- Proximal Muscle strengthening
What treatments LACK support by current evidence?
- No significant difference was noted in open vs. closed chain exercises with respect to exercise type.
- Further evidence is needed to investigate the long term effects of patella taping, the mechanism of action and direction of force (medial, neutral, lateral). Clinical evidence for the success of this intervention is still unclear due to an insufficient amount of high level evidence, inconsistency of tape application techniques, in ability to identify the precise mechanism of action, and variance in measurements of specific outcome variables.
- No date is available regarding massage, thermotherapy, TENS, electrical stimulation, and biofeedback for treatment of PFPS.
What treatments are SUPPORTED by the best available evidence?
- Tyler et al noted the role of hip muscle function in the treatment of PFPS. A 93% success rate occurred with hip flexor strength improvements and normalization of Ober (IT band/tensor fascia latae) and Thomas (hip flexor) tests.
- A case report by Mascal et al documented weakness of hip abductors, extensors and external rotators in testing of 2 patients with PFPS. Treatment consisted of recruitment and endurance training of the hip, pelvis, and trunk musculature which resulted in a significant reduction in pain, improved LS kinematics during dynamic testing and ability to return to original level of function.
- Whittingham et al investigated the effectiveness of daily patella taping and exercise on pain and function in individuals with PFPS. Results suggest that patella taping may be useful in conjunction with strengthening exercise to enhance speed of recovery.
- 2 articles were reviewed in regards to the effect of foot orthoses on PFPS. Both studies suggest that the use of orthotics in patients who present with excessive pronation resulted in improved pain/stiffness (note: multiple interventions were used in these studies, including orthosis). Patients with patellofemoral pain may benefit from the use of foot orthosis if the patient demonstrates the following: excessive foot pronation and/or a LE alignment profile that includes excessive lower extremity internal rotation during weight bearing and increased Q-angle. Additional studies are needed to assess the treatment efficacy of foot orthosis for patients with PFPS.
Strengthening of the Quadriceps is a key in the rehabilitation program (LoE:1a)
Pain-free exercises are very important when treating PFPS. Isometric exercises while the knee is fully extended (patella has no contact with condyles) can be used at the beginning of the therapy, because it minimizes stress on the patellofemoral-joint while reinforcing the Quadriceps. For example (exercise): 1. Straight-leg exercise Patient lies on his back, one knee bent at +/- 90° (! pain-free if that knee is affected by PFPS) and foot flat on the ground. The other knee is fully extended. Patient elevates extended leg and holds it for 10secs, before relaxing (concentric contraction and/or eccentric contraction is also possible, which makes it dynamic). Control that Patient keeps a normal lumbar lordosis and does not compensate with his basin. 2. Pillow squeeze exercise Patient sits comfortable with his trunk supported. Both knees extended. Place a pillow (or towel) under one knee (that knee might be slightly flexed). Patient tries to push the pillow/towel in the table by extending his or her knee. (Quadriceps contraction).
CKC are more functional than OKC and they provoke lower patellofemoral joint stress, particularly in the terminal ranges of full extension (0° to max 40° knee flexion). Therefore exercises should be practiced within this range and pain-free. Example of exercise: • Squats; be sure that the patient’s knee doesn’t come farther than his toes. Once his knee passes his toes, the stress on his patellofemoral-joint become too high and might provoke pain.
If patient is unable to tolerate CKC exercises, then OKC exercises might be a viable option because the load that will be used can be better controlled than in CKC, as long as the exercises are pain-free! When using OKC exercises, Patient should stay in within a pain-free range of motion (ROM) between 40° to 90° knee flexion.
Vastus medialis obliquus (VMO) (LoE:3b)
Training of the VMO muscle is appropriate is some PFPS patients but not all. Assessment of the vmo should assess firing, cross-sectional muscle mass, endurance capabilities, and ability to fire at different knee angles, and used functionally. Too much focus on selective activation of the VMO muscle should be avoided as there is no evidence to suggest it can be isolated. However, it is extremely important in guiding the patella into the trochlea, and hence although it is active through range, its primary role is between zero and thirty degrees flexion. The need for better VMO function is enhanced with trochlea dysplasia, patella alta, medial patellofemoral ligament rupture or when a large TTTG is present.
The VMO is particularly adversely affected by swelling and or pain. 10ml of fluid will inhibit the VMO but 40ml to inhibit the VL. Similarly pain causes vmo delay, and the more pain, the greater the delay. This helps to explain why patients post trauma and/or surgery who will often have a joint effusion, are then left with PFPS. It also explains why resolution of an effusion is a primary goal, and avoidance, and reduction of pain are also paramount. Painful exercises are a waste of time.
VMO training although not isolating to the vmo should be aimed at 0-30 degrees, incorporate endurance holds, and be prescribed with a tonic bias to represent the postural function of the muscle.
Recent research demonstrates that vmo type exercises will cause an alteration in the vmo fibre angle, (relative to the femoral axis). Fibre angle can change from a vertical 40 to a much more medialising 70 degrees.(LoE:2b)
Hip muscles training(LoE:2b)
Rehabilitation program for PFPS should also incorporate strengthening exercises of the hip abductors and lateral rotators. It has been proven that the pain during daily activities was lower and functionality was greater when knee exercises are combined with hip exercises. (Table 1 and 2 + figure 2 show which exercises were used in the research and proved to be efficient. Exercises were performed during 4 weeks)
Another research study found that PFPS patients had decreased eccentric hip abduction compared with healthy people. Thus, it is recommended to use eccentric hip abduction strengthening exercises.(LoE:3b)
It has been proven that the proprioceptive quality in the knee of patients with PFPS is decreased. Even with unilateral PFPS, the proprioception is decreased in both knees (pathological and nonpathological knee)! Therefore proprioceptive training (pain-free exercises!) of the knee should be part of the rehabilitation program.
Some patients might suffer from PFPS because of a (neuromuscular) disbalance between the VMO and VL. The main cause is muscle atrophy of the VMO and excessive/abnormal lateral tracking of the patella, due to the remaining force of the VL. In case of neuromuscular disbalance between the VMO and VL, electrical stimulation of the VMO should be considered to complement the conservative (exercises) therapy, because it is selective and does not stress the patellofemoral joint.
An example of how you can accomplish the stimulation;
The patient sits with the trunk supported extended legs with slight knee flexion and lower limb muscles completely relaxed. Following parameters were used in research (isometric contraction of the VMO):
- Electrode placing = 1 on the motor point and the other one next to it.
- Asymmetric bipolar current
- Pulse width = 0.5 milliseconds
- Pulse frequency = 50Hz
- Intensity = max. the patient can endure without pai- Time = 7 minutes => 6 repetitions, on for 6 seconds and off for twelve, and progressed to 30 minutes, 11 repetitions, on for 10 seconds and off for 12sec.
You can use EMG feedback to capture EMG activity of the VMO and VL before and after the therapy. While your patient is performing the functional test of stair stepping using the limb affected by PFPS; patient faces the stairs in standing position. He begins the movement by flexing the limb with PFPS, placing it on the first step, and then extends it in unilateral stance. In a continuous movement, he places the non-affected limb on the second step and finishing the stair stepping with full knee extension.(LoE:2b) Be aware that stepping upon a stair can be very painful for PFPS patients. Only use this evaluation technique once the Patient can perform this test pain-free. Start with a very low stair, so the compression between the patella and the femur is minimal.
The main differences you should find are increased energy consumed by the VMO muscle in order to perform the test. → Change in force-generating capacity of the muscle. And faster (more accurate) activation of the VMO muscle after therapy.
There are a few clinical predictors that can help decide if a Patient is more likely to benefit from foot orthoses or not;
- Individuals with PFPS who wear less supportive footwear,
- those who report lower levels of pain,
- exhibit less ankle dorsiflexion range of motion,
- Patient who reports an immediate reduction in pain with foot orthoses when performing a single-leg squat.
What kind of orthoses? In research prefabricated orthoses were used; made of ethylene-vinyl acetate of medium density (Shore A 55), containing built-in arch supports and 4-varus rearfoot wedging. Prefabricated foot orthoses significantly enhanced functional performance in individuals with PFPS after 12 weeks, and these improvements were greater than those observed immediately after the foot orthoses were used. These improvements may be important to long term prognosis and prevention of osteoarthritis development for some individuals with PFPS (further research is needed).
Knee Pain and Patello-femoral Pain Injury Rehabilitation Seminar | Feat. Tim Keeley | FILEX
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