Anterior knee pain is an umbrella term which covers a wide range of related but significantly different conditions resulting in pain around the patella-femoral joint
The differential diagnosis of PFPS includes chondromalacia patella and patellar tendinopathy. Both are not considered to be under the term of PFPS though patients will complain of similar symptoms, the cause is thought to be different, so the treatment is different.
The patella is a triangular bone which sits on the trochlear surface of the distal anterior femur.
Both the articular surface of the patella and the distal end of the femur are covered with cartilage. This cartilage helps to reduce friction, promote smooth movement and acts as a shock absorber.
The articular surface of the patella is divided by a vertical ridge which corresponds with the trochlear surface of the femur. Although these ridges are matched to a certain extent, they are not totally matched.
The patella is held in place partly by its bony shape and partly by the soft tissues around the knee, especially the quadriceps muscles that encircle the kneecap and form the patella tendon.
The main cause of anterior knee pain
One of the most common contributory factors causing PFP is biomechanical dysfunction. The patella and trochlea articulation are variable and for some individuals, the patella does not fit well. Also, the patellofemoral joint requires a complicated balance of the soft tissue structures that surround the joint. Unequal pull from one set of structures can cause increased force distribution between the patella and femur leading to pain. To treat PFP effectively, it is important to understand the anatomy and biomechanics of this joint.
The weakness of Vastus Medialis Obliquus give the advantage to the Vastus Lateralis to 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 patellar and result in pain or discomfort.
The opposite can happen, but a medial glide, tilt or rotation is rare.
Another muscle and ligament that can cause a patellar deviation is an iliotibial band or the lateral retinaculum in case there is an imbalance or weakness in one of these structures.
Knee hyperextension, lateral tibial torsion, genu valgum or varus, increased Q-angle, tightness in the iliotibial band, hamstrings or gastrocnemius. can indirectly cause patella malalignment and cause PFP,
Foot pronation or foot supination can provoke PFPS. Foot pronation is more common with PFPS causing compensatory internal rotation of the tibia 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 joint.
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.
Some example of anterior knee pain other than PFJ
· chondromalacia patellae
· iliotibial band friction syndrome
· patellar tendinitis
· chondral lesions
· ACL tear
Sign and Symptoms
· Pain around the patella especially during going up and coming down the stairs
· pain with kneeling and squatting
· knee giving way
· pain with long sitting
· knee crepitation and tender posterior surface of the patella
· pain during cycling or a car driving
Many things to consider during examine PFPS
• Observation-patella position, (eg tilt or lateralised),
• femoral position,
• relative muscle bulk, especially gluteals, and calves.
• Presence of effusion and or Hoffa's fat pad oedema, foot position.
• Level of hyper-mobility of tibiofemoral and patellofemoral joints.
• ROM, especially loss terminal knee extension
• Single leg stance and pelvic, femoral, foot control. Excessive use of VL.
• VMO degree of fire, speed of firing, endurance capability at zero, ten, twenty and thirty degrees of knee Flexion
• Gluteals-firing and endurance as abductor and external rotator in different degrees of hip flexion.
• Muscle length in Modified Thomas test to assess hip flexors, quads and add in adduction for TFL.
• straight leg raising lest for Hamstrings length, flexibility of gastrocnemius, soleus, gluteus maximus insertion into ITB, (adduction in hip flexion).
• foot pronation and tibial medal torsion supination and femoral external rotation
• 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.
In the early stage
Important to settle the “flare-ups” as quickly as possible.
During a flare-up, aim to reduce the accumulative load on the knee by decreasing the exercises and daily activities.
· in the presence of pain and effusion,
· pain medication [ pain killer and anti-inflammatory can be prescribed be socialist
· ice and compression
· physical modality like TENS and electric stimulation can help in reducing pain and effusion
· pulsed high-intensity LASER can help in relieving the pain and inflammation
· patella taping can help to reduce the stress over the PFJ
The insole can be used to correct foot problem (pronation or supination) which indirectly reduce the stress on the PFJ
Knee support in case of giving way or lateral or medial knee instability
As the knee settles, gradually build back up the normal activity levels.
Physiotherapy will identify the dominant “contributory factors” and provide a specific, targeted rehabilitation program.
Rehab program can last from 8-12 weeks
This may include
- Joint mobilization techniques to restore full range of movement at the joint especially last degree of knee extension, ankle Dorsi-flexion, hip joint range of motion especially extension, abduction and medial rotation
Strengthening of the Quadriceps is key in the rehabilitation program
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,
VMO muscle is appropriate in 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,
VMO primary role is between zero- and thirty-degrees flexion.
The need for better VMO function is enhanced with trochlea dysplasia, patella alta, and médial patellofemoral ligament rupture
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 the 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 the resolution of an effusion is a primary goal, and avoidance, and reduction of pain is also paramount.
Painful exercises are a waste of time.
VMO training, although not isolated 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 which increase its role in medial patella stability
Hip muscles training