Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Patellofemoral pain syndrome

Patellofemoral disorders are a common problem in all age groups. The cause of this pain is complex and not well known. It is therefore important to make a precise diagnosis, otherwise the treatment will not be successful.

Etiology
Damage to the articular surface of the patella usually occurs in individuals aged 10–25 years, and is associated with pain, especially on walking up and down hills and stairs and when squatting.

It is common for pain to occur in the knee when walking up and down hills. Compared with the normal flexion of the joint on flat ground, knee flexion increases considerably during these activities, increasing compression between the patella and the femur. Walking uphill causes less pain than walking downhill, because during ascent the knee joint is flexed at an angle of about 50° under load, while on descent it is flexed at an angle of about 80° under load. The body does not lean forward when walking downhill, so knee
flexion is controlled by the quadriceps muscles alone, increasing the compression forces between the patella and the femur.
The cause of anterior knee pain may not always be found (idiopathic pain). Possible causes are trauma, malalignment or instability.

Grading of patellar instability
Grade I/Patellar lateral tracking: owing to an increased Q angle, the patella will move laterally before moving proximally on quadriceps contraction, which will give a lateral patellar compression syndrome with a small area of contact with increased rest on the articular surfaces of the patella and the trochlea. The patella will not dislocate but will track laterally on quadriceps contraction on an extended knee. There is a negative apprehension test.

Fractures of the patella
The patella can be cracked by transverse or longitudinal fractures or shattered by stellate fractures. The injury often occurs as a result of a fall on the knee. When the fragments are displaced, surgery is required followed by use of a brace for about 4 weeks. When there is no displacement a plaster cast will usually suffice. A longitudinal patellar fracture often requires no more than bandaging if there is no displacement.

The patient should subsequently be instructed in isometric thigh muscle training. Healing time is usually 6– 8 weeks, depending on the fracture type.

Patellar tendon rupture
The patellar tendon is very strong (almost the strongest soft tissue in the whole body); it originates from the
patella and inserts in the tibial tuberosity (the prominence on the anterior proximal part of the tibia). This tendon is essential for the knee extensor mechanism, i.e. it is impossible to extend the knee unless this tendon is intact.

Ruptures of the tendon can be complete or partial. A complete patellar tendon rupture is not very common as the tendon is so strong. Biomechanical studies have shown that a patellar tendon rupture may occur during weightlifting when the patellar tendon tension at the time of failure was equal to approximately 17.5 times the lifter’s body weight. A risk factor for patellar tendon rupture is previous steroid injections

Symptoms and diagnosis
At the time of injury the athlete experiences a sudden ‘pop’ with intense pain, typically when pushing-off or landing after a jump. The disability will be immediate and the athlete cannot support weight on the injured side.

The patella will be proximally displaced and there will be a palpable cleft over the rupture site. There will be tenderness over that area and some swelling, but usually little pain. An X-ray will show a patellar bone Symptoms and diagnosis
At the time of injury the athlete experiences a sudden ‘pop’ with intense pain, typically when pushing-off or landing after a jump. The disability will be immediate and the athlete cannot support weight on the injured side.
The patella will be proximally displaced and there will be a palpable cleft over the rupture site. There will be tenderness over that area and some swelling, but usually little pain. An X-ray will show a patellar bone that is proximally retracted.

Treatment
A complete patellar tendon rupture, which may be proximal or distal, is treated surgically. Usually it is enough to suture the tendon back to bone, but occasionally it has to be reinforced by addition of tissue such as, e.g., the hamstring tendon. Rehabilitation is slow, with a gradual increase in range of motion and thereafter strengthening. Return to sports may be possible after 6–8 months. Cycling and sports such as golf may be possible before that.

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