The thigh muscles on the front of the thigh, known as the quadriceps, are one of the biggest and most powerful muscle groups in the body and very important functionally. The quadriceps allows us to get up from sitting, to go up and go down stairs, to manage slopes, to walk and to run, and it has to be strong to stabilise and move our body weight. The strength of the quadriceps can be affected by injury, disuse or arthritis of the knee joint and the muscle loses strength very quickly if not used normally.
The quadriceps means "four heads" in that the upper parts of the muscle originate in four different areas and all narrow down towards the knee where they join into the fibrous quadriceps tendon, collect the patella and continue to insert on the bump below the kneecap, the tibial tuberosity. Initial management of a weak quadriceps is to diagnose any reason for the weakness and remove it, whilst recording the degree of weakness being demonstrated. Early strengthening work involves restoring the range of movement of the knee and working on full extension control so the knee can be fully straightened with control.
A common gym exercise is the knee extension machine, where the person sits on the machine and straightens the knee against a pad which is connected via cams to the weights. Although it seems like a good exercise it is very unnatural in function as this movement does not really occur in normal life, and the stresses are placed strongly on the area of the patellar tendon. This exercise may be useful in the early stages but for further strengthening more functional movements are required.
Squatting related movements such as gym ball squats, squatting, one leg bends and leg presses are more functional exercises and can be appropriately progressed. Forces are transmitted through the hips and the knees at normal angles and the muscles around these joints co-contract to achieve the raising or lowering of the body weight. Weights can be progressed steadily as these muscles are very strong and may need significant intensity of stimulation to become stronger.
Final strengthening needs to include co-ordination, balance and joint position sense so the physiotherapist will include active and dynamic exercises involving control of the knee joint in challenging manoeuvres. The physio then progresses the patient to sport specific exercises as fitness for an activity is closely related to performing the specific movements required by that activity.