The quadriceps muscle is the large muscle fount in front of the thigh. The main action of this muscle is to extend the knee joint. The muscle is attached by a tendon (quadriceps tendon) at its lower end to the patella (knee cap). If this tendon is torn, the patient become unable to extend his knee.
A normal tendon is strong and cannot be torn except if subjected to strong forces e.g. sudden contraction of the quadriceps muscle on falling from a height. However, certain conditions may weaken the quadriceps tendon, making it prone to tears. These conditions include:
- Rheumatoid arthritis
- Renal failure
- Certain antibiotics
In such cases, the tendon may be torn by a moderately strong trauma.
The patient feels sudden pop associated with severe pain in the lower part of the front of the thigh. The patient becomes unable to extend the knee (except if the tear is partial). The knee feels unstable and the patient may fall if the knee is bent just a small degree.
On examining the patient, a gap may be felt just above the patella (knee cap). The diagnosis can be confirmed by MRI which shows the exact site of the tear.
Some minor partial tears may be treated by putting the leg in a splint for a few weeks to allow healing of the tendon. However, the majority of cases are treated surgically by suturing the tendon or reattaching it to the patella.