Quadriceps tendinopathy

Quadriceps tendinopathy is a painful condition of the quadriceps tendon, which lies above the kneecap and helps transmit the force of the quadriceps to the patella and then to the patellar tendon. It mainly presents as anterior knee pain, located above the kneecap, at the insertion of the quadriceps tendon on the upper pole of the patella, and usually occurs in a context of repeated overload of the knee extensor mechanism.

It is particularly common in athletes whose sport involves jumping, running, accelerations, changes of direction or squats. Jumping sports such as basketball, volleyball and some racket sports are particularly affected.

The term “quadriceps tendinitis” is commonly used, but quadriceps tendinopathy is more appropriate in chronic forms: the issue is less an acute inflammation than a change in the tendon’s capacity to withstand the stresses placed on it.

The quadriceps is made up of four muscles — the rectus femoris, the vastus medialis, the vastus lateralis and the vastus intermedius — which converge into the quadriceps tendon. This tendon inserts mainly on the upper border of the patella and forms part of the continuous extensor mechanism: quadriceps → quadriceps tendon → patella → patellar tendon → tibial tuberosity. This continuity allows the force produced by the quadriceps to be transmitted to the tibia.

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Function of the quadriceps tendon

The main function of the quadriceps tendon is to transmit the force of the quadriceps to allow knee extension, propulsion, jumping, running, climbing stairs, braking when landing from a jump and controlling knee flexion. The quadriceps is therefore not only used to “straighten the leg”: it also plays a major role in the eccentric control of the knee.

Quadriceps tendon and patellar tendon: what is the difference?

These two tendons belong to the same extensor mechanism but are not identical: in quadriceps tendinopathy, the pain is mainly located above the kneecap, whereas in patellar tendinopathy it is mainly located below the kneecap, most often at the lower pole of the patella or in the patellar tendon. This distinction is important because the two conditions can cause very similar anterior knee pain.

Biomechanics

The quadriceps tendon is subjected to particularly high stresses when the quadriceps has to produce or control a high force: jumps, landings, accelerations, decelerations, changes of direction, heavy squats, uphill and downhill running, fast running. During a jump, the quadriceps must produce a large force to propel the body; on landing, by contrast, it must actively brake knee flexion. The tendon must therefore be able to both produce and absorb large forces.

The main mechanism of pain is generally an imbalance between the load applied to the tendon and its capacity to withstand it. A healthy tendon can withstand very high loads, but its capacity to adapt is not instantaneous: a sudden increase in load can exceed it — for example, an athlete who is not usually exposed to jumping and abruptly takes up basketball, volleyball, tennis, heavy squats or interval training again.

The term “tendinitis” suggests inflammation, but in chronic forms the reality is more complex: tendinopathy corresponds to a set of structural, cellular, mechanical and biochemical changes. Acute inflammation may play a part in certain phases, but it does not on its own explain chronic symptoms — treatment therefore does not simply consist of “removing the inflammation”, but above all of restoring the tendon’s mechanical capacity.

Quadriceps tendinopathy is particularly common in athletes whose sport involves jumping, running, accelerations, changes of direction or heavy squats. Jumping sports such as basketball, volleyball and some racket sports are particularly affected, as are people who do strength training involving heavy squats or plyometric work introduced too abruptly.

A particularly high-risk situation is returning to a jumping sport after several months without practice (for example, little sport over the summer followed by an abrupt return to basketball): the tendon has not necessarily lost all its capacity, but it is no longer prepared for this specific load.

Quadriceps tendinopathy usually develops when there is an imbalance between the load applied to the tendon and its capacity to withstand it. Several factors can contribute to its onset.

Load-related factors

A sudden increase in training volume or intensity, a return to sport after a break, more frequent jumping sessions, more strength training sessions or heavier squat loads, and the abrupt introduction of plyometric work are the main load factors.

Biomechanical factors

A lack of strength in the quadriceps or hip muscles, poor lower limb control, poor tolerance of eccentric loads or a marked increase in the stresses on the extensor mechanism also contribute to the onset of symptoms.

Individual factors

Certain general factors can also alter the tendon’s capacity to adapt; however, they should be regarded as contextual factors rather than as a single cause.

The classic picture is that of an athlete describing pain just above the kneecap when jumping or squatting. At first, the pain may appear only after training, after a jumping or strength session, and then it may gradually appear during squats, jumps, running, on stairs or during everyday activities.

The main symptom is anterior knee pain, usually well localised at the upper pole of the patella, at the insertion of the quadriceps tendon — the patient can often point precisely to the painful area with one finger. Typically painful activities are jumping, landing, squatting, climbing stairs, running, accelerating and decelerating. A feeling of stiffness may be present at the start of activity, after a period of inactivity, or the day after a demanding session.

Jump-related pain may appear on take-off, on landing or during repeated jumps — particularly important information for athletes in jumping sports. During a squat, the pain may be absent at small angles, present when the knee bends further, and greater with additional load: this gradation helps assess the tendon’s capacity to withstand different loads.

Clinical examination

The examination looks at the precise location of the pain, tenderness on palpation, pain on quadriceps contraction, during squats or single-leg exercises, quadriceps strength, lower limb control, hip and ankle mobility, and any signs of patellar or intra-articular pathology. The diagnosis is mainly clinical.

Palpation looks for pain specifically at the upper pole of the patella, over the insertion of the quadriceps tendon — pain reproduced precisely at this site is an important finding, which should always be weighed against the other clinical findings. A resisted contraction of the quadriceps (knee extension, isometric contraction) may reproduce the pain; pain localised to the tendon strengthens the diagnostic hypothesis.

The squat is a particularly useful functional test: it shows when the pain appears, the depth at which it occurs, movement quality, symmetry, knee control and tolerance to repetition — it can also be used to monitor progress during rehabilitation. The single-leg squat assesses quadriceps strength, knee stability, pelvic control and lower limb coordination, in conditions closer to the demands of sport.

Surgery is rarely necessary in uncomplicated quadriceps tendinopathy. It may be considered in cases of very disabling chronic tendinopathy, prolonged failure of well-conducted rehabilitation, a significant partial tear or major functional loss; data on surgery for chronic tendinopathy remain limited and indications must be individualised.

The situation is different in the case of a quadriceps tendon rupture, an acute condition very different from simple tendinopathy. It usually occurs suddenly, combining a strong contraction of the quadriceps with sudden flexion of the knee, with a snapping sound, sudden pain, a tearing sensation, swelling and a significant loss of strength. The main functional sign is difficulty or inability to actively extend the knee (difficulty lifting the straight leg, walking or climbing stairs), sometimes with a palpable gap above the kneecap. A complete rupture is a relative orthopaedic emergency and must be diagnosed quickly; MRI makes it possible to determine whether it is complete or partial, its location, the degree of retraction and any associated injuries.

A complete rupture is generally treated surgically, in order to restore the continuity of the extensor mechanism, active extension, quadriceps strength and knee function. Post-operative rehabilitation is then progressive and much longer than for simple tendinopathy: protection of the repair, gradual recovery of mobility, reactivation of the quadriceps, progressive strengthening, functional work, running, jumping and plyometrics, then a sport-specific return — a progression guided by functional criteria rather than by time elapsed alone.

Recovery time depends heavily on how long the symptoms have been present and how severe they are, the sports load, the tendon’s capacity to be reloaded and the possible presence of a structural lesion. A mild form may improve within a few weeks, whereas chronic tendinopathy may require several months of rehabilitation. Avoid considering the tendon “healed” simply because the pain has disappeared after a few days: its mechanical capacity must be rebuilt gradually.

Prevention mainly relies on the extensor mechanism having a good capacity to withstand sporting loads: regular quadriceps strengthening, unilateral work, work on the glutes, hamstrings and calves, power exercises and plyometric exercises.

It also involves a reasonable progression in jumping and training volume, avoiding abrupt returns to a jumping sport after a prolonged period of inactivity.