Wimbledon this week makes us think more about tennis – and maybe encourages us to get out and play ourselves! Why should we be concerned about our knees in this sport in particular?
There is a lot of side to side and forward and back movement in tennis, which is done in positions of knee flexion for almost the entire match except for serving and overhead smashes. This means that the knee cap is under a lot of pressure.
At around 20-30 degrees of knee flexion, the knee cap enters the groove in the femur called the femoral groove – see picture below. This results in an increased compression effect between the back of the knee cap and the femur itself. If the muscles in front of the knee (quads) are contracting, as they would be if you are racing around the court in a semi squat position, then the muscle contraction forces the knee cap into the groove harder resulting in more compression. This can then create a softening of the patella cartilage and lead to the development of patellofemoral pain syndromes.
Patella tendon injury is what Rafa Nadal was suffering from recently and is also common. Also called ‘jumpers knee’ - tennis players do jump a lot. The repetitive jumping type motion under high stress, can overload the tendon and cause injury due to repetitive strain.
The meniscus is the soft cartilage structure in the knee that acts as a shock absorber between the tibia and femur. The most common mechanism of injury is twisting the knee on a fixed and planted foot. This is exactly what tennis players do a lot. The fixed foot position also relatively fixes the tibia in the lower leg. The femur is then free to pivot and shear across the meniscus. This can lead to slow progressive breakdown or if done suddenly and with great force, it can acutely tear the meniscus. This then creates internal knee pain, a locking/catching sensation and a knee that always swells.
Bursa are fluid filled sacs that protect the tendons around the knee from rubbing against bone. The dynamic acceleration/deceleration forces on the knee seen in tennis demands strong muscle contraction to stabilise the knee. This can lead to tendons being rubbed over and over again against the bursa and it becomes inflamed. This leads to pain particularly when bending the knee.
You can see that the requirements of extreme movement over and over again when playing tennis can create knee overload and probelms that affect your performance. This year’s Wimbledon has claimed four players with knee injuries, and by Sunday the 30th June, we may see a few more pull out due to knee complaints.