Wednesday, May 18th, 2016
There are many types and causes of knee pain. Knee pain is thought to constitiute 41% of chronic cycling injuries. In this article I review the causes of pain directly over the kneecap which is made worse by cycling. You may have heard of the terms patallofemoral pain (PFP), chondromalacia patellae or runners knee which are all used to describe pain around or under the kneecap.
Kneecap pain is not limited to cyclists; it is common with up to 25% of sport participants complaining of this type of pain.
Common symptoms of patella femoral pain can include:
· Pain located around or under the kneecap noticed when cycling, prolonged sitting, stair climbing, kneeling, hopping, running
· Gradual onset, not related to any traumatic event such as a fall, twist, or knock
· Stiffness after sitting for long periods
· Crepitus or crunching noises under the knee cap
What causes the pain?
In order to understand how it occurs, it is useful to understand the structure of the knee and the kneecap (patella). The kneecap is a triangular shaped bone that runs in a groove formed by the thigh bone (or femur). At the top the quadriceps tendon inserts into it, below the patellar tendon connects it to the shin bone (or tibia) and from each side fibrous tissue that surrounds the knee join attach to it, and from the right side it also receives attachments from the vastus medialis oblique (VMO).
The kneecap moves in this groove when the knee bends and straightens. When the kneecap does not track properly in the groove, it can rub on the sides of the groove leading to pain and inflammation. In these cases the kneecap tracks too laterally i.e. it tends to track more to the outside of the knee. Due to the excessive lateral tracking, stress can also be placed on the fibrous tissue on the inside of the knee. This can also be a source of inflammation and pain.
Anything that changes the way the kneecap moves in the groove can lead to patellofemoral pain. This can include:
· Imbalances between the muscles on the outside (lateral quads, ITB) of the leg versus the inside (VMO): the lateral muscles can put a stronger pull on the kneecap than the VMO can meet, leading to weakness and strain of the VMO. The VMO is particularly susceptible to weakening after knee injury where the leg is immobilised or full range of knee motion is restricted for a period of time. Sometimes clients will report a feeling of strain or tenderness just to the top inside of the knee which they can feel by pressing when the knee is bent. They notice it during cycling, running or stair climbing. This can be a sign that the VMO is weak, and if not addressed could later lead to pain around the kneecap.
· Studies have shown that tight ITB, weak gluteus medius and abductors, weak external rotators, and weak core can give rise to instability in the pelvis. Pelvic instability can cause the thigh bone (femur) to rotate inward more than usual. This might be observed as a side to side movement of the knee when extending the leg during the downstroke, instead of the desired linear movement of the knee as you push down on the pedal. This changes the orientation of the groove so the kneecap does not track in it properly leading to pain. A rough test of your pelvic stability would be to perform a lunge or squat and note whether the knee rolls inwards as you perform it. Your knee should keep pointing straight and not dip or turn inwards. Excessive hip dipping while cycling would also be another indicator that the gluteus medius and abductor s are weak.
· Increased foot pronation. Pronation is the rolling inwards of the foot during walking or running or cycling. Excessive pronation or over pronation can lead to problems at the knee. While this movement happens at the foot, it also causes a compensatory movement in the shin bone which affects the alignment at the knee impacting the kneecap and causing pain.
· The position of the shin bone, excessive inward or outward rotation of the lower leg can affect the alignment at the knee. It has been suggested that people with low arches may be more susceptible to PFP than those with normal arches as low arches change the alignment of the shin bone. The positioning of your cleats can affect the position of the shin bone and the rotation of the lower leg.
· Leg length discrepancies: when setting saddle height only one leg is correctly fitted to the pedal meaning that if the bike is fitted to suit the shorter leg, there will be increased compression of the kneecap in the groove and pain. Leg length discrepancies can occur due to rotations at the pelvis, or more unusually, if you were born with them.
Bike Set up & Training
· When cycling, a saddle set to far forward will increase the wear and tear forces on the knee and the likelihood of knee pain. Similarly cycling with the saddle too low will have the same effect. As mentioned above your cleat positioning will also affect the rotation of the shin bone and possibly impact your knee.
· Training: sudden increases in training, a lot of hill work, or cycling in high gears with low cadence can cause problems.
What can you do to help it?
The best thing to do is to get assessed and rehabilitation from a therapist familiar with the sport. They will advise you on what needs to be strengthened, work out tight muscles, perform mobilisations to realign the pelvis and correct leg length if needed, tape your knee, and determine whether to refer you for orthotics should you need them. Also consider seeing a bike fit specialist to ensure your bike setup is optimal.