Dr. Kevin Yip

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

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Patellar Instability or Mal – Tracking

SYMPTOMS

The knee feels unstable or weak, or gives way in association with recurrent pain around the anterior part of the knee, with or without preceding trauma. It is particularly common in young female athletes.

AETIOLOGY

This condition can be caused by inherited conditions such as patella baja or alta, genu valgus or muscle imbalance around the knee. It can develop after a previous patella dislocation.

CLINICAL FINDINGS

Occasionally there is effusion but most commonly there are few clinical findings. An increased Q-angle and hyper-mobility can raise the suspicion of this diagnosis.

INVESTIGATIONS

Clinical examination is the most important tool for diagnosis and should include tests for all ligaments and other structures in the knee. Xray is valuable to rule out patella abnormalities. A three-dimensional CT scan taken at different knee angles can help measure the level of mal-tracking. MRI and arthroscopy may be important for evaluating alternative diagnoses. There is a high risk that cartilage on the kneecap as well as on the femur condyle will have been damaged if there was a previous dislocation. The combination of partial ACL rupture and patellar instability is not uncommon.

TREATMENT

An athlete with anterior knee pain and recurrent instability of the patella should be seen by an orthopaedic surgeon and a physiotherapist. Most cases can be treated without surgery and with physiotherapy, working in particular on muscle strength and control of the entire kinetic chain. In cases with an increased Q-angle of over 20 degrees, surgical treatment with anterior medialisation of the tuberositas tibia may be indicated if physiotherapy fails.

REFERRALS

Refer to Dr Kevin Yip (+65 9724 1219) consultant senior orthopaedic surgeon forfurther investigations to verify the diagnosis. Physiotherapists should be involved in close collaboration with the surgeon.

EXERCISE PRESCRIPTION

Cycling and water exercises are good alternatives to keep up general fitness. Valgus stress to the knee should be avoided so breast stroke is not recommended. Rehabilitation back to full sport usually takes around six months.

EVALUATION OF TREATMENT OUTCOMES

Monitor clinical symptoms and signs. Different functional knee scores for different sports are available to measure when the knee allows a return to full sport.

DIFFERENTIAL DIAGNOSES

Meniscus tear, chondral injuries, OCD, medial plica syndrome, chondromalacia patellae, quadriceps insufficiency, Sinding-Larsen’s syndrome, patellar tendon disorders, referred pain, secondary symptoms from ankle or back insufficiency, core instability and more.

PROGNOSIS

Good-Fair. Appropriate treatment will allow a return to professional sport within three (non-operative) to six months (after surgery).

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