Glossary
Quadriceps tendon
Quick answer
The quadriceps tendon is the thick tendon just above the kneecap that joins the four thigh muscles to the top of the patella. It transmits their pull so you can straighten the knee, and it is also a common graft source for ACL reconstruction, explains Dr. Pablo Gelber, knee surgeon at Aman Hospital in Doha.
What it is
The tendon is formed where the rectus femoris and the three vastus muscles merge, in layers, a few centimetres above the kneecap. It attaches across the top of the patella, and some fibres pass over its front to blend with the patellar tendon below. Together, the quadriceps, its tendon, the kneecap and the patellar tendon form the extensor mechanism.
Why it matters for patients
A quadriceps tendon rupture usually happens when the muscle contracts hard as the knee is bent, for example stumbling on stairs or landing awkwardly. It is more common in people over 40 and in those with diabetes, kidney disease, gout or long-term steroid use. People often feel a pop, see a gap above the kneecap and cannot lift the straight leg. A complete tear needs prompt surgical repair, ideally within days to a couple of weeks.
Irritation of the tendon from overuse, quadriceps tendinopathy, causes pain just above the kneecap in jumping and squatting sports. A strip of this tendon is also used as a graft in ACL reconstruction.
How it is examined
A surgeon feels for a gap and tests whether you can raise the leg with the knee straight. Ultrasound or MRI confirms a partial or complete tear.
Frequently asked questions
I cannot lift my straight leg after a fall. What should I do?
Seek prompt medical assessment. Inability to lift the straight leg after a fall can mean a tendon rupture or kneecap fracture, which do better when treated early.
Does taking a quadriceps tendon graft weaken the knee?
A strip is taken and the rest of the tendon remains. Strength is rebuilt during rehabilitation, and the graft site usually recovers well.
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