Patello femoral joint... or steam train?

Patello femoral joint... or steam train?

Patello femoral joint…or steam train?

‘Gammy knees’ are a very common affliction. Although dramatic high speed injuries seem all too common when watching sport on TV, in reality, the most common knee issues simply creep up on us in a far less impressive fashion.

In modern times, our adult legs no longer run from wild animals, climb trees or walk miles for water. As a result, some of the crucial muscles that control our leg movement patterns become lazy. This means that the load on our knee cap is often not ideal.

Even the slightest biomechanical glitch can develop into a painful problem with enough repetition. Think of how many times your knees bend and straighten everyday!

Most people with knee cap issues have a combination of biomechanical (alignment) and impact volume issues. Once this type of knee pain sets in, it can be very stubborn to settle. These contributing factors are often very easy to correct, however, so avoidance is, by far, the path of least resistance!

Anatomy

The main knee joint is made up of our femur (thigh bone) and the tibia (shin bone). Sitting on the front of the main knee joint is the patella (knee cap). The patella is a small, round, floating disc, which is fully incorporated into the patellar tendon. This tendon is the ceremonious end of the quad (thigh) muscle.

The patella exists to distribute the force of the powerful quad muscle over our bending knee. If the patella didn’t exist, the patellar tendon would wear away on the underlying bones very quickly. With the patella bone in place, the knee can bend and straighten, again and again, with the tendon happily safe from excessive wear.

The underside of the patella has a longitudinal ridge, and the femur underneath it has a longitudinal groove. As the patella slides up and down on the femur with the movement of our knee, the ridge slides beautifully in the groove – like a train on a track.

What goes wrong?

The train staying beautifully on the track relies on the quad muscle pulling the patella evenly and in correct alignment. If the strength in the quad muscle is uneven, or the upwards pull is in a somewhat wrong direction, there is trouble at the station.

The quad muscle in our thigh is made up of 4 parts: one towards the inside of your thigh, two parts on top of each other in the centre, and one towards the outside of your thigh. Unfortunately, the inside part (which we call VMO due to a hideously long latin name) is always looking for an excuse to slack off and be lazy. Things like prior knee injury, poor leg biomechanics and poor fitness can all lead to a lazy VMO. This means that, when the quad pulls on the patella, the pull from the outer part of the quad is stronger than from the lazy inner ‘VMO’ part of the quad. This is not good news for the train, which grinds on it’s tracks as it is pulled slightly to one side.

In the patella, this causes pain.

Alignment is another issue. I want you to try this: Stand up, and do a small squat, keeping your back straight and your heels on the ground – it’s just a small knee bend really. Freeze in the bent knee position. Now have a look down: is the space between your knees smaller/the same/ or greater than the space between your feet?

Your knees SHOULD be the same distance apart as your feet. If you draw a line straight down to the ground from the middle of your patella, it should fall to your middle toe. In this position, the quad is pulling vertically up towards your hip in a straight line, putting an even pull on your patella.

In many people, however, the knees fall closer than the feet in their mini squat position. This means that the quad has to pull on an outward angle towards the hip, therefore grinding once again on the train and track.

In reality, VMO weakness and poor knee alignment usually co-exist, so a number of factors plot against the patellar tracking, creating pain. 

Correct                                                Incorrect

Some people never realize that they have poor leg alignment and poor VMO strength until they push their knees to do more than they are accustomed to. The start or increase of a running program, a new Boot Camp or a change to a more physical job can all be triggers for the onset of patella pain. The more rapid these changes are made, the more likely it is that patellar pain will develop.

What can be done to prevent this?

The first suggested exercise is to get your VMO working better:

STRAIGHT LEG RAISE

1. Lie on your back - you may prop on your elbows

2. Rotate the leg very slightly outwards

3. Squeeze the quad and lift the leg up straight, about half a meter off the bed/ floor

4. Lower the leg nearly to the bed/floor

5. Perform 20 repetitions. Do 2 sets

Next, awareness is the key – notice when your knees are dropping in towards each other when they shouldn’t. Repeat the small squat we did earlier, but this time, make sure your knees are above your toes. Get used to what it feels like to have your knees bending in the right position. Sometimes it helps to think of lifting the arches of your feet, or of holding a beach ball between your knees.

A word of warning – don’t OVER correct. The solution is NOT to simply stand on the very outside edges of your feet and jam your knees out! Your still need all of your toes on the floor! Let’s not create NEW problems while trying to fix existing ones, eh!?

If persistent knee pain is an issue for you, it may be time for some physio help. There is a great progression of exercises that we can tailor to your needs to get you feeling better.

Karen Finnin

Musculoskeletal Physiotherapist

karen@physios-online.com