The knee is made up of two main joints. The joint between the thigh bone (femur) and shin bone (tibia) is called the tibiofemoral joint and the joint between the knee cap (patella) and thigh bone is known as the patellofemoral joint. The patellofemoral joint is at the front of the knee and problems here can also sometimes be called anterior knee pain. Whenever you bend and straighten your knee the patella slides up and down in a groove in the femur called the trochlear groove. Both the patella and the trochlear groove are lined with some of the thickest cartilage in the body to withstand the pressure put through the joint when we walk, run, climb stairs and any other activity that involves movement at the knee. It is important that during these activities the patella runs in the centre of its groove to keep the pressure spread out over the whole joint so that one part is not ‘over-loaded’.The videos below show how the patella moves as we bend and straighten our knees.
HOFFAS FAT PAD
Another very important structure in the patellofemoral joint is Hoffa’s Fat pad. This lies just below the patella and underneath the tendon that joins the pattela to the tibia (patella tendon). This fat pad has lots of nerve that can produce pain
The 2 main sources of pain from the Patellofemoral joint come from irritation of the fat pad and overloading pressure on the patella and trochlear groove.
FAT PAD IMPINGEMENT
The fat can be inflamed after direct pressure onto the front of the knee such as a fall onto the knee or due to hyperextension at the knee. Hyperextension is when the knee goes past its normal straight position. This can occur during trauma if you misplace a step and ‘snap’ your knee back or have direct pressure pushing the knee back when it is already straight. Also repetitive, small hyperextensions at the knee can cause impingement of the fat pad. This can occur when running if you over stride with your foot landing in front of your knee.
Activities such climbing stairs, running, hill walking put huge pressure through the Patellofemoral joint. Repeated pressure alone on the cartilage does not produce pain as the cartilage itself has no nerves that produce pain. However, if the load through the joint is greater than it can tolerate due to increased training or degeneration of the cartilage, pressure is transferred to the bone underneath which does have pain nerve endings.The way that we move and exercise can increase the load through the patellofemoral joint. The most common problem that increases the risk of over-loading the joint is dynamic knee valgus. This is when the knee turns in towards the other knee as the foot is on the ground.
Rest and reducing activity that increases the load through the patellofemoral joint are important initially. Treatment such as joint mobilisation and ultrasound may be helpful in the short term but commonly the way that we move needs to be corrected. If the root cause of your movement faults are not identified and corrected appropriately it is likely that the problem will never fully recover and will return as soon as you start increasing any exercise. At the Performance Lab we specialise in movement analysis and correction. We can perform slow motion running analysis, use equipment to identify even the smallest difference in muscle strength and range of motion and have years of experience to get you back on track