Pain at the front of the knee joint is a very common complaint, with estimates that 1 in 4 adults will suffer this problem at some point in their life. For such a common issue, the knowledge surrounding the varying causes of this pain and how to treat them effectively is extremely poor.
This is not helped by the vague terminology used to describe such cases. Anterior knee pain and Patellofemoral Pain Syndrome are the most commonly used names, which when broken down, simply describe just one symptom and the location of that symptom.
No wonder many clinicians are confused or unsure of the many different possible diagnoses that can be covered by these two blanket terms. For example, the term Patellofemoral Pain Syndrome can be used to cover around six types of pathology, which can then be further subdivided into more specific injuries, all of which with differing treatment plans depending on the cause of the symptom.
It's easy to see why using these vague labels often results in unsuccessful treatment outcomes. When it comes to knee pain conditions, specificity is the key.
The following conditions are all often lumped together under the vague anterior knee pain description. However, a little more investigation and understanding can help define the exact cause of pain, which leads to a more worthwhile treatment approach.
Patella Compression Syndrome
There are two forms of compression syndrome that can occur at the knee. Both are due to compression of the patella against the underlying trochlea groove of the femur and result in degenerative changes to the articular cartilage of both surfaces.
Excessive Lateral Pressure Syndrome
This occurs when soft tissue tightness around the lateral aspect (especially the lateral retinaculum) results in a laterally tilted or laterally shifted patella. Medial pain may also occur due to overstretching of the tissues.
Global Patella Pressure Syndrome
In this form of compression, the soft tissue tightness is more universal surrounding the patellofemoral joint, resulting in the patella being compressed more centrally within the trochlea. This is more common after surgery, immobilization or traumatic injury.
Patella instability
This is usually a predisposed issue, maybe due to global joint laxity or a shallow trochlea, so treatment can be very difficult. Recurrent dislocations or subluxations are a great clue, as is excessive lateral glide of the patella, which persists at 30-degree knee flexion.
Biomechanical dysfunction
The knee is subject to forces coming from both above and below it. Movement dysfunctions, muscle imbalances and structural abnormalities can all have a negative impact. Common problems include hip abductor and external rotator weaknesses, which allow the knee to fall into adduction and internal rotation during the stance phase.
This medial motion throws the patella out laterally, resulting in friction and eventual changes in the articular cartilage lining the patella and trochlea. Excess or prolonged pronation at the subtalar joint is another potential causative factor due to the resulting increased internal rotation at the tibia.
Direct patella trauma
Falling on to the knee(s) or a direct impact from, or on to, something hard can cause injury to the knee. If recognized by the patient as a linking factor, this makes diagnosis easier. However, in many cases, unless significant pain at the time which persists continuously, the fall or impact is forgotten and the connection lost in the patients mind.
Injuries in this category may include articular cartilage tears, bone bruising or even patella fractures.
Soft-tissue lesions
There are several soft-tissue structures in the front of the knee joint that can become injured and should always be considered when anterior knee pain is present.
Plicas
Synovial plicas are folds in the synovial lining that can become irritated through repeated friction. The most commonly agitated is the suprapatella plica found just above and medial to the patella. This is most common in cyclists due to the repeated greater knee flexion and extension that's seen in runners, for example.
Fat pad
The fat pad is easily palpated on either side of the patella tendon. It can become damaged through a sudden impact and is highly innervated, resulting in considerable discomfort.
Medial Patellofemoral Ligament
The MPF ligament, found to the inside of the patella, can be injured during a traumatic dislocation or subluxation injury, or more gradually due to repetitive strain as the patella is pulled laterally in cases of ELPS. It can be extremely tender on palpation, but should always be compared to the contra-lateral side.
Overuse injuries
This form of injury includes Patella Tendinopathy - a degenerative condition of the patella tendon; Quadricep Tendinopathy - a similar but less common condition of the quadriceps insertion above the patella; And Osgood-Schlatters and Sinding-Larsen-Johansson apophysitis', affecting the tibial tuberosity and inferior pole of the patella, respectively.
Treatment protocols
Once the most likely origin of pain has been established and the causative factors highlighted, a treatment plan can be proposed to address both areas. As mentioned above, each case is different, even between individuals with the same condition and so no two rehabilitation programs are ever the same.
There are common features or aims that should be met:
- Reduce pain and swelling
To make the patient more comfortable, allow rehabilitation to begin and prevent quadriceps inhibition.
- Restore muscle control in the quadriceps
Often reduced or inhibited after long periods of pain, swelling or post-traumatic injury.
- Develop strength in the hips
Hip abductor and external rotator strength is vital for good knee function.
- Enhance global flexibility
Reduced range of hip, knee and ankle mobility can negatively affect knee function.
- Improve neuromuscular control and proprioception
Enhancing the body's control over its movements and awareness of its positioning.
- Gait retraining
Re-education on walking patterns, as well as other movements performed regularly
- Gradual return to activity
Whilst maintaining rehabilitation exercises. Aids such as taping or supports may be used in the initial stages.
