A ruptured quadriceps tendon is an injury to the tendon that connects the quadriceps muscle to the patella. The tear can be partial or total. A rupture of the quadriceps tendon is a rare but serious injury. If this injury is not recognized immediately and operated on in a timely manner, it can lead to disability.
The quadriceps tendon originates from the muscular union of the rectus femoris, external flat, medial flat and medial flat at the upper pole of the patella. The quadriceps tendon in combination with the patellar tendon and patella form the extensor mechanism of the knee. A rupture of this central tendon drastically prevents knee extension and directly affects functionality. The degree to which a rupture of the quadriceps tendon limits knee extension depends on the severity of the tendon damage. Minor tendon tears may have minimal impact on extensor function, whereas complete tears may completely inhibit knee extension.
Ruptures of the extensor mechanism of the knee as a whole are very rare, but are reported to have a high morbidity and disability rate. This injury has historically been more common in men over the age of 40 years. Rupture of the quadriceps tendon often occurs during high-energy activity with a poor landing. During landing, a large force is applied to the knee in flexion, the distal leg is fixed to the ground and the quadriceps makes a rapid, eccentric contraction. Another mechanism involves the force applied directly to the anterior surface of the knee. Patients usually present with acute knee pain, swelling and functional loss. Other symptoms include instability, inability to walk, inability to extend the knee, palpable gap and hematoma at the site of the tear. If the patient is not diagnosed in the acute phase, the diagnosis of the rupture becomes more difficult and can be easily missed.
Imaging tests usually do not offer much in quadriceps tendon injuries. However, ultrasound may have some clinical utility, as it detects tendon rupture and assesses the degree of rupture. It has also been used sequentially to assess healing and to determine the presence of associated haematomas, collections or calcifications. Radiographs are not usually helpful in diagnosis, but may have some clinical utility to rule out other related injuries or conditions. Radiography may be useful in determining the position of the patella. A high patella position may be indicative of a patellar tendon rupture, whereas a low patella position may indicate a quadriceps tendon rupture. An MRI scan details the extent of the damage.
In the case of a partial tear, the knee should be immobilised for 3 – 6 weeks, at 10° flexion. In the case of a complete rupture, surgery is mandatory and should be performed as early as possible (72 hours after the injury at the latest) so that the tendon can be reattached to the patella. After surgery, the knee is immobilised for 4-6 weeks. Two days after surgery, intensive isometric quadriceps exercises may be started. During the period of immobilisation, the weight load is gradually increased so that full load is achieved after 6 weeks. Kinesitherapy is then started to regain full range of motion of the knee.