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Persistent knee pain

In the final part of our series orthopaedic surgeon Mr Rob Pollack covers persistent and recurrent knee pain.

In the final part of our series orthopaedic surgeon Mr Rob Pollack covers persistent and recurrent knee pain.

Most knee pain is transient and will respond to a period of rest and anti-inflammatory medication. But persistent knee pain warrants clinical assessment and, in some instances, investigation and referral. This article will discuss the management of persistent knee pain – rather than pain after an acute knee injury, which was covered in last week's article.

Causes of knee pain

Keep a list of differential diagnoses in mind to direct history-taking and examination. Also bear in mind the pain may be referred from the hip or spine. Not infrequently, patients experiencing pain in the knee will have a normal knee joint but an arthritic hip or an intervertebral disc prolapse.

I find it useful to think of knee pain as anterior, medial, lateral or inflammatory – a guide to conditions related to pain type is below. Several patterns of symptoms are often seen and if these patterns can be recognised the diagnosis will become obvious.

Common clinical scenarios

• The sporty teenager with pain on exercise and tenderness over the tibial tubercle. Probable diagnosis: Osgood-Schlatters disease.

• The young fitness fanatic who has pain on exercise. Possible diagnoses: patellar tendonitis (jumper's knee), ilio-tibial band friction syndrome, an old meniscal tear or osteochondritis dissecans.

• The 30- to 40-year-old female who experiences anterior pain when climbing up and down stairs. Probable diagnosis: chondromalacia patella.

• The 50-year-old male with varus knees and pain on exercise. Probable diagnosis: early medial compartment osteoarthritis with or without a degenerate tear of the medial meniscus (see pre- and postoperative pictures, above right).

• The 50-year-old female patient with valgus knees and pain on exercise made worse on climbing stairs. Probable diagnosis: patellar maltracking combined with early patello-femoral osteoarthritis.

• The 50- to 60-year-old old patient with intermittent pain associated with large effusions. Probable diagnosis: flare-up of osteoarthritis, gout or pseudogout.

Clinical assessment

41237193After asking a few preliminary questions I find it useful to continue taking the history with the patient on a couch and both knees exposed. The patient can then show you exactly where they experience the pain and tell you what brings it on. Early on I form a list of potential diagnoses based on the anatomical location of the pain and this list is then refined after asking pointed questions and performing specific clinical tests. Often it's not possible to make the exact diagnosis at this stage but it is always possible to make a plan for further management.

Knee alignment – varus or valgus – will be immediately apparent.

Muscle wasting is a reliable sign that genuine pathology is present.

Check for an effusion – the textbooks talk about grading of knee effusions but this is clinically unhelpful. Essentially, if the effusion is big enough to allow a patella tap, it is significant. Sometimes a boggy ‘fullness' can be felt in the suprapatella region indicating presence of a synovitis.

I always test the range of motion with my hand on the patella, feeling for crepitus and assessing patella tracking. This is particularly important in patients with anterior knee pain.

Range of motion should be compared with the normal knee. Loss of knee flexion or extension compared with the normal side is more relevant than the absolute range of motion.

Joint line tenderness may indicate the presence of a meniscal tear or a degenerate medial or lateral compartment.

Stability of the knee should also be compared with the normal side, although ligamentous instability isn't usually painful.

Finally, I always check the hip has a full range of painless motion, perform a sciatic stretch test and examine the foot pulses.

Investigations

If the diagnosis is clinically obvious – for example, the patient with classic chondromalacia patella – no investigations are required. But if not, blood tests, imaging or a combination of both are warranted.

In the patient with an inflammatory arthropathy – an effusion and a synovitis – it is worth performing a CRP, ESR, urate, rheumatoid factor and human leukocyte antigen B27. It is also worth aspirating the effusion and having it analysed for the presence of crystals.

In patients with mechanical symptoms or those that have ongoing symptoms despite treatment, imaging is essential. Plain X-rays should always include three views; AP, lateral and skyline. They will show the presence of osteoarthritis and loose bodies but in the majority of patients with soft tissue causes for pain they will be normal. The investigation of choice is an MRI scan which will give the diagnosis in the vast majority of cases. MRI is particularly good at identifying soft tissue pathology such as tendonitis, meniscal tears, damage to the articular cartilage and so on, but it will also identify osteoarthritis before it becomes apparent on plain X-rays.

When to aspirate and inject

If a patient has a large, non-traumatic effusion it is worth aspirating at least once and sending the fluid for microscopy. This will help make the diagnosis and also relieve symptoms. In patients with an inflammatory arthropathy, aspiration followed by steroid injection is worthwhile. It is not something that should be repeated often but is worth doing for the occasional flare-up.

When to refer for physiotherapy

The vast majority of patients will have ‘non-surgical' pathology. Some will improve simply with rest and anti-inflammatories. Those who continue to experience symptoms warrant referral for physiotherapy. The physiotherapist will usually be able to relieve the symptoms in the short term but also help prevent the problem recurring in the longer term.

When to refer to an orthopaedic surgeon

The following groups of patients should be considered for referral:

• Patients with ‘surgical' pathology based on a high index of clinical suspicion or identified on MRI. By this I mean pathology requiring surgical intervention such as a meniscal tear, loose body or osteoarthritis.

• Patients who have failed a course of non-operative treatment and are still symptomatic.

• Patients whose symptoms warrant an MRI scan which can only obtained in the hospital setting.

• Patients with ‘non-surgical' pathology who don't require surgery but need the multidisciplinary approach that an orthopaedic surgeon can offer. This includes radiologists who can perform ultrasound-guided injections and a particular physiotherapist with whom the surgeon has a close link.

Mr Rob Pollock is consultant orthopaedic surgeon at The London Clinic and Royal National Orthopaedic Hospital

For more information about The London Clinic telephone 020 7935 4444.

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