Anterior Knee Pain
Anterior knee pain is a common occurrence in distance runners. The knee is under influence from the foot below and the lumbo-pelvic girdle above. These influences dictate the range, load and pathomechanics placed on the knee.
The most common types of anterior knee pain in runners are;
- · Patello-femoral pain (PFPS)
- · Patella tendinopathy
- · Fat Pad impingement
Patello-femoral pain is more of a syndrome – a cluster of symptoms rather than a well defined pathology. It is characterised by non-specific pain anteriorly, medially and often superiorly above the actual joint. There is sometimes a small amount of fluid present in the superior pouch above the knee known as an effusion. It is often aggravated by increased load to the patella-femoral joint such as stairs, squats, lunges and downhill running particularly where the joint is required to stabilise against eccentric actions.
Commonly, swelling and effusion cause the VMO to decrease activity, which further destabilizes the joint. The joint cavity becomes inflamed causing a synovitis. This is acts as a chemical irritant to local nociceptors
This is often more involved in sports where jumping is common however, it also occurs in distance runners. The onset is gradual, similar to most tendinopathies warming up with activity only to progressively get worse as the tendon struggles to adapt. Pain is usually located at the inferior pole (bottom of the patella). In these cases the tendon may be thickened especially in long standing tendinopathies. Without appropriate management the prognosis is usually longstanding with a poor outcome.
A common factor involved in tendinopathies is the inability to bare the load through the myofascial system due to fatigue or poor firing patterns. This is evident in longstanding tendinopathies where the quad decreases in size and often strength. This gives way to poor load transference from the muscle to the tendon. Instead the tendon takes the load. Over time, this changes the microstructure of the tendon causing weakness and pain.
Fat Pad Impingement
The fat pad is a cushioned portion of padding sitting below the patella and behind the tendon. This is thought to absorb load and reduce the friction between the tendon and underlying surface. This is susceptible to impingement as the knee goes into extension particularly at end range. Hyperextension is the typical cause of injury with tenderness on palpation and a puffy appearance. The pain is quite localised and assessment is made by taking the knee into slight hyperextemsion with over pressure, and palpation directly to the fat pads. Palpation reveals exquisite tenderness and may co-exist with PFPS.
Runners who overstride will have an increased risk due to increased knee flexion/extension angles. Generally females have an increased size of their fat pads and may be at increased risk of impingement. Further, individuals with a patella that sit with the inferior pole tilted towards the fat pad increase compressive forces through this structure.
- · Increase in hill work (particularly downhill)
- · Increase in volume
- · Poor recovery between bouts
- · Poor lumbo pelvic control
- · Biomechanics – overstriding due to posterior pelvic tilt or anterior pelvic shift – the classic ‘swayback’
- · Increased Q angle
- · Anatomical considerations ie; shallow femoral groove
- · Increased pronation
- · Overactive ‘tight’ hamstrings
- · Poor lateral/medial stability of patella
Fig 1. Anatomy of the patellofemoral joint, including the tibiofemoral joint. Structures inside the joint that may be the source of pain are not depicted.
Treatment involves modifying or identifying the causative factor. Addressing the symptoms only by focusing on the knee will not provide positive long term outcomes. As previously stated the knee is heavily influence by the hip above and the foot below thus these factors need strong consideration. This could not be overstated in a closed chain exercise such as running.
Modifying hill work and volume is seemingly easy, though hard to do when there is no objective view. Make sure you receive professional advice when modifying load, volume and intensity. Addressing these factors will affect recovery in a big way!
Perhaps the biggest factor for runners is lumbopelvic control and biomechanics relating to overstriding. Weakness and poor timing of the hip abductors has been shown to influence normal functioning of the knee. That is, poor strength will cause valgus or varus positions of the femur dragging the patella with it causing an alignment issue. Alignment issues will irritate the underlying patella surface and over time may cause degenerative changes to the boney architecture.
In terms of acute treatment the first step is minimising the swelling and inflammation. The standard protocol to reduce this with rest (load modification), ice and compression will help as will washing soda for acute subcutaneous effusion. Washing soda is quite alkaline drawing the fluid across the skin. When applied for a few hours or overnight – good results are usually seen. Care must be taken when left on for long periods as it may irritate the skin.
Increased Q angle is an anatomical design that affects women more than men. As females usually have wider hips the angle between the femur and the patella is increased. This factor changes biomechanics such that there is an increase in peak hip adduction, hip abduction and varus forces on the knee.
Other anatomical factors such as a shallow femoral groove or ‘tilted’ patella are best recognised and managed. Keeping load at a manageable level is the best option.
Overstriding is best addressed with feedback from an outside source (this will give objectivity). There are too many sources of feedback and proprioception going on to assess yourself. Changing stride length and pattern needs to be driven from the control of lumbo-pelvic area in conjunction with consideration to foot positioning – not just where it lands but how it lands.
Overactivity (usually ‘tight’ hamstrings) affects the knee by decreasing quad function exposing the joint and tendon to greater loading. Altering biomechanics will go a way towards addressing this. Further treatment can be achieved by soft tissue treatment to the affected area(s), hamstrings, TFL, psoas, glute min and med. Treating the inhibitory factors ie; the structures that decrease ability of those soft tissue that we want to assume the work load.
Strengthening the local area around the knee can be effective if it is part of an overall plan. Simply strengthening the VMO with end range leg extensions will not necessarily translate to increased stability during the gait cycle.
Further treatment options such as awareness taping and rigid style knee brace taping can be quite effective in poor patella-femoral alignment. Kinesio taping is receiving a lot of publicity and is in its infancy in the public eye (although, it has been around since the 80’s in terms of rehab).
Summary of treatment options:
- · Load modification
- · Biomechanics
- · Lumbopelvic stability and control
- · Soft tissue therapy
- · Joint mobilisation (in the case of stiff joint segments)
- · Awareness taping (short term)
- · Kinesio taping (proprioception and increased firing of muscles)
- · Stretching to areas of increased tone and tightness
- · Addressing foot position and function
The knee is subject to large forces. Knee pain is one of the most common reasons distance runners attend a health care clinic. Keeping the lumbopelvic area and foot position controlled will help decrease injury risk factors to the knee.