Posts Tagged ‘patello femoral syndrome’
Anterior knee pain is a very common complaint among people who participate in sports and in the general public. Over the years many theories have been developed to try and understand the cause of anterior knee pain. It has been blamed on lower limb mal-alignment (“patello-femoral syndrome” – the most common diagnosis given to this condition in people engaged in sports activity and also known as “anterior knee pain” and “runners knee”), on muscular weakness, on hyperlaxity, over training, cartilage failure (“chondromalacia patella”) and more. A sub-type of knee pain, knee instability, has been discussed elsewhere. Also, this article will not discuss the various non-idiopathic reasons for anterior knee pain (such as obvious anatomical variations, fracture, trauma, tumor, inflammation of various structures within the knee joint and around it, Osgood-Schlatter disease or Sinding-Larsen-Johansson syndrome).
The various anatomical structures and mal-alignments blamed for anterior knee pain range from the hip to the feet. Unequal leg length, external rotation of the femur, increased Q angle, pes planus, high riding patella (‘patella alta’) or low riding patella (‘patella baja’) – these are just examples. Another cause often blamed as a cause for anterior knee pain is weakness of the cartilage behind the patella – “chondromalacia patella”. This is probably only true in a minority of cases. These are all static causes of knee pain and the evidence supporting them is rather poor. It is now believed that most anterior knee pain is due to defects in dynamic factors.
Symptoms of anterior knee pain
Anterior knee pain, as its name implies, is a cause of pain in the patellar area. However many patients describe pain around or even behind the patella. Pain is aggravated by activity and especially walking up or down stairs (or a hill), squatting and running. Another type of complaint is stiffness or discomfort in the knee / knees after sitting for a prolonged time with knees flexed.
That being said, unilateral knee pain should sometimes be investigated further. The term ‘anterior knee pain’ and the aforementioned obscurity that surrounds it usually relate to bilateral pain. Unilateral pain may have another cause (even if it is gluteus medius weakness, as stated).
A symptom to look out for is the knee giving way. Giving way of the knee can be part of anterior knee pain, however it can also insinuate that there is knee instability or patellar dislocation.
Examination of a patient with anterior knee pain
The knees should be inspected and palpated. Both legs should be compared and obvious malalignment or structural abnormalities should be noted. There are several maneuvers that help make the diagnosis:
- Single leg squat – This maneuver can disclose patellar instability or a weak gluteus medius. If the gluteus medius is weak the knee on the affected side will bend inward and a normal knee will stay straight. A weak vastus medialis oblique will be evident because the patella will move outward and up.
- Patellar glide – this test assesses the mobility of the patella. Anterior knee pain can be a result of a patella that is too tight or too mobile.
- Patellar tilt – The patalla is grasped while the leg is extended and the lateral side is lifted. This should be possible at least to 0 degrees. If the patella can not be tilted this means the lateral structures are too tight.
- Patellar grind (patallar inhibition test) – The patella is compressed while the leg is extended (the patient is lying down). The patient contracts the quadriceps. If pain is elicited, this is a positive patellar inhibition test.
Proven risk factors for anterior knee pain
Risk factors for anterior knee pain can be divided into local risk factors around the knee and systemic / general risk factors that involve the whole body. The following are proven general risk factors for anterior knee pain:
- Obesity
- Lack (!) of physical activity or improper training
- Young age (especially if over active)
- Depression
Local risk factors for anterior knee pain are related to abnormal knee tracking. This means that the patella does not move in the exact proper plane it should, thus being exposed to higher than normal forces and thus suffering pain. Examples include patellar malalignment, muscle dysfunction or uncoordination, muscle weakness, patellar hypermobility or too tight lateral structures etc. Some of these risk factors are inborn, while others are acquired after surgery, trauma or wrong training habits.
Treatment of anterior knee pain
The treatment of anterior knee pain is usually conservative. Surgery is rarely if ever indicated. Treatment consists of relative rest, but not complete rest. Specific exercises are deployed to strengthen the quadriceps and specifically the vastus medialis. Gluteus medius strengthening is also warranted. The idea behind these exercises is correcting the patellar improper tracking.
If osteoarthritis is suspected to play a role in a particular patient’s complaints, then osteoarthritis treatment can be tried. Other forms of treatment such as better fitting sneakers, braces and taping can be tried with varying success rates.
Surgical options for anterior knee pain treatment include lateral release (if it is assessed that the lateral forces on the patella are too tight), proximal realignment and distal realignment.
Further reading
- Management of patellofemoral syndrome. American Family Physician. 2007; 75: 194-202.
