A synopsis of diagnosis and management - Introduction
The patello femoral compartment of the knee is a common source of pain and symptoms in the knee. The aim of this section is to provide a simple guide and outline for the diagnosis and management of patients presenting with anterior knee pain.
In general pain can be thought of as an emerging from the patello femoral joint in the patients who describe that it is their “knee that hurts”. This means that when a patient presents complaining of pain alone then the aim of questioning is to determine whether the source is the medial compartment (indicating a meniscal or degenerative problem), lateral compartment, again indicating meniscal or degenerative problem, or the patello femoral structures and anterior compartment. When patients state it is their “knee” that hurts they usually grasp the front part of the knee indicating the anterior compartment rather than pointing with a finger to the medial or lateral compartments specifically.
Overview of Patello Femoral Problems
The following classification and description of patello femoral problems is given as a guide for a decision making in anterior knee pain problems.
Definition and Description
Objective patella instability
Greater than 1 dislocation
Potential patella instability
Always abnormal anatomy
Painful patella syndrome
No anatomical abnormality
Only anterior knee pain
Essentially this categorisation is dividing patients into those with a potential for patella dislocation, defined as potential patella instability, those who have had clear episodes of dislocation and those patients with normal anatomical alignment producing the subcategory of “painful patella syndrome”. This subcategory can be further subdivided as follows.
Painful Patella Syndrome:
Over used knee
Post traumatic anterior knee pain
Patella infra (contracted patella tendon)
In order to lead to a conclusion for which subcategory of patient fits in, the following three questions need to be considered when assessing a patient presenting with anterior knee pain or patello femoral problems.
Three Questions for Patello Femoral Problems:
Is there mal-alignment?
Is the problem in the peri-patella tissues?
Is this simple overload?
Mal-alignment is the term used in assessment of patello femoral problems indicating that the patella is not sitting in its proper place and the joint surface and tissues are therefore under abnormal load. There is clearly a spectrum of mal-alignment problems: from true dislocation at one end of a spectrum, where the patella is pulled off to one side, and mild mal tracking, where the patella does not track centrally in the trochlea groove at the end of the femur where it is meant to sit.
The mainstay of diagnosis is therefore directed at excluding or detecting abnormalities of alignment and tracking of the patella (see later).
The Peri-patella Tissues
There are various specific causes of anterior knee pain and patello femoral problems that are related to the tissue around the knee. These are isolated diagnoses and are summarised as follows:
Overload problems: what is the source of pain
Articular cartilage itself does not have any pain fibres and pain seems to originate from either the subchondral bone or the soft tissue surrounding the knee, which are densely innovated. A likely theory is that overload on the patello femoral joint results in an increase in pressure in the subchondral bone and leads to the sensation of pain. This explains the treatment rational for reducing overload on the patello femoral joint and thereby reducing pain.
Remember other causes of knee pain.
It is important not to remain too focused on the knee as a source of pain. We must not forget that knee pain may be felt from radicular origin (spine) and the hip (childhood conditions of Perthes and SUFE plus adult problems of hip OA).
Obtaining clues from description and history
Pain: most patients report anterior knee pain which is typically activity related and tends to be worse on climbing or descending stairs. Symptoms in the athlete are exaggerated after running over hilly ground. Symptoms are classically worse when sitting with the knee bent for prolonged periods such as in a cinema or car.
Instability and giving way: patients describing this symptom are likely to have problems with true patella dislocation or recurrent subluxation (patella seeming to slide laterally during a twisting movement). This needs to be differentiated from the buckling of the knee on pivoting associated with ACL rupture. Subluxation is virtually always lateral due to the pull of the quadriceps muscle.
Mechanism of injury: a direct blow to the anterior part of the knee such as falling on a concrete step will tend to result in traumatic anterior knee pain and impact damage on the articular cartilage of the patella or the corresponding trochlea surface. Landing on the anterior tibia may drive the tibia posteriorly, causing an injury to the posterior cruciate ligament resulting in the tibia sagging and overloading the patello femoral joint.
Insidious onset of symptoms: this usually indicates that there may be an anatomic pre-disposition to anterior knee pain or specific training activities may have caused an overuse problem and this may be well recognised and treated with retraining
The key features on examination: examination should confirm that the pain is originating from the patello femoral compartment of the knee and as such this will involve attempts to reproduce the symptoms. The main aims of examination are therefore:
Assessment to answer the question: is there mal-alignment?
The simple quick key steps to assessing mal-alignment are:
1 Standing alignment (bare foot).
2 Assessment while sitting.
3 Supine assessment of patella mobility.
5 Tender points.
6 Other tests.
Other subtle tests can be performed looking for tightness of structures. These could include assessment of quadriceps flexibility by lying the patient prone and assessing the ease the knee bends heel to bottom. Iliotibial band flexibility is assessed by Obers test. The detail of this is outside the scope of this section.
The examination detailed above combined with use of the classification at the beginning of this section will lead to various management options.
1 Objective patella instability.
In this scenario patients have sustained true patella dislocation, often on several occasions and it would be expected to find abnormal anatomy with poor patella tracking.
Management: patients should be referred for orthopaedic opinion as they are likely to need corrective surgery for the misalignment. A rehabilitation programme should be commenced. It would be essential to try at least 2 – 3 months of appropriate rehabilitation before undergoing surgery.
2 Potential patella instability.
In this situation the patella may never have fully dislocated but the patient may experience symptoms of the patella jumping or sliding nearly out and distrust in the knee. It is usual then to find signs of abnormal alignment.
Management: referral for physiotherapy rehabilitation programme which would commonly involve taping and probably the use of a patella supportive brace. Referral for orthopaedic opinion could be delayed awaiting outcome of rehabilitation which stands a high chance of helping. Persistent subluxation symptoms are however bad and raise the chance of later degenerative change. Early surgical correction is far preferable to late osteoarthritis.
3 Painful patella syndrome.
In this situation there will be normal anatomical alignment and the patient will generally complain of anterior knee pain localised to the patello femoral compartment area.
Management: this depends on the underlying diagnosis.
4 Primary painful patella syndrome.
When this occurs in the teenage female then a conservative approach with physiotherapy is best adopted with procrastination, avoiding the temptation for surgery.
5 Overused knee.
This is diagnosed when there are no obvious anatomical abnormalities and there has been some activity that has prompted overuse of the knee. Again a rehabilitation programme would be directed at detecting and altering the precipitating factor.
6 Secondary problems
Background information on rehabilitation options for treatment
As would be noted from the management overviews outlined above, patello-femoral rehabilitation is a key part to treatment of these problems. Specialist physiotherapists with an interest in this area are key to the management and certainly aid in the diagnosis of these problems. Multiple treatment modalities are available including an exercise programme, soft tissue stretching and pain management. The use of biofeedback principles, orthoses and analgesics are also very important.
Specific programmes of exercise vary between practitioners, but are likely to include:
In general, closed kinetic chain knee extension exercises, with the foot on the ground - are preferred. These are in preference to open chain exercises as excessive patello femoral joint forces can be generated when the foot is not in contact with the ground. Eccentric exercises are especially important for specific areas of tendinitis.
Patella taping is also a key element to rehabilitation and physiotherapy. In this method taping is applied to the patella to re-direct the tracking and therefore reduced pain. Patients can be taught how to apply taping themselves. The principle is that once symptoms are under control the taping can be discontinued. At this stage, the patient’s own muscle balance has returned to control patella tracking and overload. It should be stressed to patients that taping on its own is unlikely to be effective - it must be combined with stretching and strengthening as outlined above.
Further details on these aspects can be obtained from the rehabilitation department.
Background Information on Surgical Options for treatment
This section looks at the potential surgical treatments that are employed for patello-femoral problems and outlines the scope of the treatment modalities.
Arthroscopy is generally not the first line treatment or investigation for patello-femoral problems. It becomes indicated if there are mechanical symptoms and signs affecting the joint. Options for treatment using the arthroscope include:
More information on arthroscopy can be found in Appendix A.
2 Medial Patello-Femoral ligament (MPFL) reconstruction.
Over the last fifteen years or so, the importance of the medial patellofemoral ligament (MPFL) as the primary soft-tissue restraint to lateral displacement of the patella has become recognised. Rather than being a distinct ligament - such as the anterior cruciate ligament - it is formed by a concentration of fibres of the joint capsule. It is most active over the first 30 degrees of flexion, beyond which the trochlea groove is engaged by the patella.
The MPFL can be ruptured following lateral dislocation of the patella. Where the bony anatomy is relatively normal then rebuilding the MPFL is the procedure of choice to stabilise the patella.
In the most commonly-employed surgical procedure, the gracilis tendon is first harvested as a single graft. It is then used to recreate the tension between the medial border of the patella and the attachment of the MPFL to the medial epicondyle of the femur. Proper anatomical positioning of the graft is crucial to the surgical outcomes. Cases of medial subluxation, medial articular overload and recurrent lateral instability have all been reported as a result of improper surgical technique.
3 Bony re-alignment of distal structures.
This option involves transposing the tibial tubercle towards the medial and anterior direction depending on the type of misalignment. The effect of this is to reduce the lateral pull on the patella by the quadriceps.
These procedures are less commonly performed since the advent of MPFL reconstruction but the main types of osteotomy performed include:
These surgical procedures require the use of a protected range of movement brace after surgery, for four to six weeks as the bone heals, followed by a two to three months rehabilitation programme.
One of the causes of an unstable patella is trochlear dysplasia, meaning that the trochlear groove of the femur is too shallow or uneven. One option for dealing with this is to aim to reshape the anatomy of the trochlea surgically. Various options are available, including deepening the groove, or raising the lateral wall, depending on the specific problem. This is usually an open operation.