Diagnosis and management of knee injuries
With the changes in society, activity levels, longevity and patient expectations,
musculoskeletal problems are one of the overwhelming problems facing the NHS.1 As sports participation increases in the adult population, and increasingly sports are continued into middle age and beyond, patients are sustaining more activity-related knee injuries and are less willing to accept the inability to undertake their chosen pastime, whether it be running, golf, bowls or walking.
Adolescents and their parents are no longer willing to accept adolescent knee pain as the norm, or as ‘growing pains' that will inevitably resolve. Arthroscopy is now one of the most common operation performed worldwide and with the increasing use in the management of sports injuries, anterior knee pain and the treatment of early arthritis, its use will undoubtedly continue to increase.
Knee injuries are the most common case of presentation to A&E,1 and their treatment presents a significant proportion of work in the primary care setting. Careful assessment of the injured knee is necessary to identify those which require urgent investigation or referral to secondary care.
The accurate, effective and efficient management of knee problems at the point of presentation is therefore important in terms of the effective use of time and health care resources. This demands an initial working diagnosis and triage of patients into those who are
self-limiting or minor problems for whom no specific treatment other than rest and non-steroidal anti-inflammatory drugs (NSAIDs) are necessary, and those for whom physiotherapy assessment and treatment is required. However, the more significant injuries for which further investigation, magnetic resonance imaging (MRI) and orthopaedic management will prove necessary should be identified as early as possible so that expeditious referral can take place.
Generally I am concerned if, by the end of taking the history, I have not formed a fairly accurate working diagnosis or at least have a short list of possibilities. Increasingly I tell myself to listen carefully to the patient, who is trying to tell me the diagnosis and who only needs a little help to describe the relevant features.
Three important factors for knee
• The nature of the injury or onset of the condition
• The activities which exacerbate the symptoms
• The site of the pain.
Identifying these characteristics can greatly help in formulating the working diagnosis.
Anterior cruciate ligament (ACL) injury There is always an acute injury with a pop, instability, immediate swelling, generalised pain and inability to continue the activity. Knee instability is common particularly when twisting or on rough ground. The pain is felt generally deep within the knee unless a meniscus is also torn.
Acute meniscal injuries These commonly present as a squatting, kneeling or twisting injury, with localised pain and overnight swelling. Pain is usually located on the medial or lateral aspect of the knee and is exacerbated when twisting, squatting or on stair climbing.
Patients with meniscal injuries may also have pain when lying on their side at night, commonly they say it is painful when their knees touch together. Age does not exclude the possibility of meniscal injuries for which arthroscopy may be curative. Figure 3 (page 9) shows the arthroscopic appearance of a normal medial meniscus.
Osteoarthritis In osteoarthritis there is usually generalised pain which may be located on the medial, lateral or anterior aspect of the knee and is exacerbated when active or walking, and worse at the end of the day. Advanced osteoarthritis is a characteristic cause of knee pain at night.
Anterior knee pain Patients with anterior knee pain commonly experience pain while descending hills or stairs, sitting for prolonged periods with the knee bent or when driving. Pain is usually relieved by rest and at night. Characteristically, patients with symptoms of synovial plicae (developmental synovial folds) within their knee (a common cause of anterior knee pain) present with episodic painful clicking or momentary catching in the knee when descending stairs or jumping. Patients with chondromalacia complain of a generalised retro-patellar ache during and after activities.
The history of the effect of movement and activity is important. Again, characteristically, patients with anterior knee pain exacerbate their symptoms when descending hills or stairs. Patients with meniscal problems have pain on twisting or crouching. Overuse injuries such as patellar tendonitis occur after a certain distance of running and then continue to ache after the activity has stopped. The pain from a synovial plica, on the other hand, is episodic and once the knee has clicked the pain disappears and activity can be immediately resumed.
Examination of the Knee
Perhaps the greatest help in diagnosing knee injuries is to identify the site of the pain. While some patients can place one finger exactly on the spot, other patients are unable to identify where they experience the pain. However, most patients can be persuaded to place one finger on the site where they experience most of the pain.
If patients can do this, then in almost all cases the patients have identified the anatomical structures involved. For example, patients with meniscal tears invariably point to the medial or lateral joint line; patients with a loose body will point to where the lump appears; and patients with patellar tendonitis will point to the inferior pole of the patella. However, some conditions do present with more generalised symptoms which cannot be accurately located. These include chondromalacia or patello-femoral arthritis, which presents with a generalised retro-patellar ache after activities, or ACL injuries, where the patient generally identifies the pain as deep within the knee.
In GP meetings or lectures, I always find the greatest interest is generated by an instruction and practical session on the proper examination of the knee. If this is not a confident part of your practice, then I would suggest one of your local orthopaedic surgeons would be delighted to come and provide a practical teaching session. For certain characteristic signs and symptoms that may be helpful in identifying particular knee conditions, see table 1 (page 6).
The Working Diagnosis
As with all disciplines of medicine it is important to remember the traditional practice of history, examination and formulation of a working diagnosis. The working diagnosis is important when communicating with patients and in formulating the primary care triage decision. If the patient is referred to a physiotherapist, then the physiotherapist will usually provide some feedback on the diagnosis and the proposed programme of treatment. If X-ray or MRI investigation is necessary, then the accuracy of the radiologist's report is entirely dependent on the detail provided in the request.
Depending on the working diagnosis the radiographer may select various options for the MRI. These include the angle and plane of the slices shown. This is important for ACL injuries and patello-femoral problems where angled oblique slices are used. Special magnetic sequences and spin sequences may be used in particular conditions, such as patellar tendonitis or articular cartilage damage (see figure 2, page 5).
the role of MRI
MRI is an invaluable tool in the diagnosis and management of knee problems. However, the costs are considerably more than standard X-rays. The costs may vary widely, depending on the facility used. This presents problems with decisions as to which knee injuries should be investigated by MRI and whether this should be in primary or secondary care.
If an MRI is obtained in the primary care setting, then usually the clinician will be entirely guided by the result. This may result in a referral for treatment of a meniscal tear or bone bruise. However, if the MRI scan is negative, then the patient will be reassured and not referred on for specialist management. While this may be appropriate, it must be borne in mind that MRI is overly sensitive in demonstrating meniscal tears. Indeed, 50 per cent of active asymptomatic men of 45 years will have a positive scan for a meniscal tear.2,3
Thus the decision as to whether to refer the 45-year-old soccer player or golfer with a meniscal tear for specialist orthopaedic opinion, and indeed for surgery, must be a clinical one supported by the MRI report and not solely an MRI-based decision. Synovial folds or plicae are not well shown on standard MRI and therefore a patient presenting with persistent painful clicking and catching in the knee might be expected to have a normal MRI and a clinical diagnosis is necessary. It must also be remembered that some other conditions such as articular cartilage defects or patellar tendonitis are not well demonstrated on conventional MRI, which may be negative. With a good radiologist, special MRI sequences may be used to improve the diagnostic accuracy of the scan (see figure 2, page 5).
Therefore, while MRI is an invaluable diagnostic tool it must not replace the clinician, and the strengths and weaknesses of the modality should be borne in mind. The accuracy can be improved if the radiographer is provided with a working diagnosis on the request form, which then enables special sequences or MRI techniques to be used where appropriate. In the face of persistent significant symptoms, do not entirely rely upon a negative MRI and conversely, beware the positive MRI for a meniscal tear, especially in the middle-aged sportsperson where there are no symptoms referable to a meniscal tear.
Other conditions such as osteoarthritis and perhaps patello-femoral dysplasia are still best investigated by conventional radiographs. Particularly in osteoarthritis, the extent of the degenerative changes and decisions as to when it is appropriate to undertake joint replacement, and also the assessment of the need for a tibial osteotomy, are still best undertaken using conventional radiographs. For a summary of the strengths and weakness of MRI, see table 2 (right).
Knee injuries usually present as acute or chronic. In the acute setting the initial decision is whether the patient requires early referral to secondary care or further investigation and management in primary care. If the condition can be initially managed in primary care, then a schedule of treatment is necessary and a time set for a review. Reassessment after 4–6 weeks is usually necessary, and if insufficient progress has been achieved then the diagnosis and treatment plan may need to be reassessed. The management of the initial condition may include rest, immobilisation or splints, protected weight bearing, physiotherapy or commonly anti-inflammatory drugs.
NSAIDs are widely used; they are very effective and can usually be administered safely. The usual cautions should always be provided with respect to allergies, gastric problems and asthma. In certain conditions such as overuse problems or the ageing sportsperson, it may be effective for the patient to take NSAIDs an hour or two before sport or only on the days they are active. Often minor problems can be effectively managed in this way. I have to confess to using NSAIDs before golf sometimes to ease various overuse conditions.
NSAIDs are powerful anti-inflammatory agents and may, in the longer term, delay the inflammatory response and healing, and so may not be indicated in some problems or for long-term problems where the diagnosis has not been made. Sometimes more significant pain control is required. In this situation, the combination of NSAIDs and paracetamol is effective.
Management of Acute Knee Injuries
Presentation of acute knee injuries raises the initial dilemma as to whether the condition should be treated in primary care. In the case of knee injuries where there has been a fracture, dislocation, acute haemarthrosis or tendon rupture immediate referral to secondary care will be necessary. Patients should be made as comfortable as possible, the knee immobilised, analgesia provided and transport to secondary care arranged.
Immobilisation can take many forms. In the primary care setting a plaster cast is probably inappropriate. More readily a reusable removable knee splint can be applied to the knee as support. The use of the traditional Robert Jones bandage is really a thing of the past, as the time and material taken to apply and re-apply it are impractical. Use of crutches and protected weight-bearing in the acute setting may be necessary if patients cannot bear weight without pain.
A haemarthrosis commonly results from an intra-articular fracture or a ligament injury; it usually forms within an hour of the injury and presents with pain, swelling and resulting stiffness of the knee. A patient with a haemarthrosis following an injury requires referral to secondary care, radiographs or an MRI scan and careful assessment. A sympathetic effusion usually forms over many hours or commonly overnight, and the effusion is not as tense or painful as an acute haemarthrosis.
Some conditions such as gout or infection may also result in a rapid onset of pain, swelling and stiffness in the knee, however there is usually no history of an injury and there are other markers for inflammation or infection present. A diagnostic aspiration of the knee and a bacteriological analysis for infection or crystallography for gout may prove diagnostic. Diagnostic aspiration should only be undertaken in a sterile situation where access to laboratory investigations is readily available. Where there is a significant chance of intra-articular infection, there is always the chance of rapid deterioration and articular cartilage damage if treatment is delayed, so early referral to secondary care is the correct option.
Knee injuries which present in the acute setting with a sympathetic effusion or other condition which does not require early intervention may be initially managed in the primary care setting. Appropriate analgesia and NSAIDs can be administered, and the knee should be rested and supported while the acute symptoms settle. This may require a removable knee immobilising splint.
Early review of patients is necessary to ensure that the knee is settling, and that the pain and swelling is resolving. The opportunity should be taken to reassess the working diagnosis and determine whether further investigation by X-ray or MRI is necessary. If the acute symptoms are settling, then early referral to a physiotherapist may be appropriate to begin rehabilitation and mobilisation of the knee. Prolonged immobilisation of the knee is to be avoided wherever possible.
Chronic Knee Injuries
Presentation of a chronic knee injury in the primary care setting allows more time for assessment, investigation and treatment before referral to secondary care if necessary. It is important to remember to allocate health care resources such as MRI appropriately and to avoid overloading the orthopaedic service with minor problems – problems which will spontaneously resolve or where the symptoms are controlled by a restriction or alteration in the patient's activities with, of course, the patient's agreement.
Conversely, where an ACL injury is suspected and the knee is giving way, or where there is a meniscal problem and the knee is locking, there is no benefit from delaying a surgical opinion. Indeed, each episode of giving way can be associated with further damage to the articular surface and significant long-term problems. Neither is there much purpose in investigating such an injury with an MRI in the primary care setting when referral for a surgical opinion is inevitable.
Where the symptoms are mild or moderate, or may possibly resolve in the short term, a trial of conservative and non-operative treatment may be undertaken. In these situations a confirmation of the diagnosis by X-ray may be helpful to confirm the diagnosis before a period of appropriate treatment. Such non-operative treatment commonly involves rest (or a partial cessation of sports), support by a splint or support, and NSAIDs.
Physiotherapy assessment and advice about mobility, work, training, flexibility, strengthening and footwear is often invaluable in addition to any programme of mobilisation, electrotherapy or rehabilitation which may be prescribed.
Patients with chronic injuries should be regularly reviewed at periods of 4–6 weeks to ensure that the programme of treatment is effective and the patient's symptoms and functional abilities are improving. If the degree of improvement proves unsatisfactory, a modification of the treatment protocol or further investigation may be necessary. Patients who are not making satisfactory progress, failing to improve or deteriorating may need to be referred for a secondary orthopaedic opinion. Early review of such patients will ensure that they are not overlooked or deprived of appropriate surgical treatment where necessary.
Anterior Knee Pain
Some chronic knee conditions which may follow injuries are difficult to manage and resistant to physiotherapy and non-surgical measures. The management of significant or prolonged anterior knee pain, chondromalacia or RSD (reflex sympathetic dystrophy or algodystrophy) is a specialist and complex area and presents various diagnostic and treatment difficulties. If these conditions are significant, restricting function or prolonged, then referral to secondary care is appropriate. While some orthopaedic surgeons would not always welcome referral of patients with anterior knee pain, it is increasingly recognised that a sizeable proportion of these patients are significantly handicapped by what is a considerable and painful problem that is sometimes amenable to specialist management and/or surgical intervention.
Perhaps the problem facing the primary care practitioner is to find a physiotherapist or orthopaedic surgeon experienced and enthusiastic about managing these patients.
Overuse Knee Injuries
With the explosion of sporting activities and prolongation of participation into middle and old age, overuse injuries are all too common. The symptoms are localised to a particular soft tissue anatomical structure. The symptoms usually occur as a result of excessive activity in an ageing sportsperson. The onset can be precipitated by a particular activity, minor injury or just start spontaneously.
The symptoms can often be controlled by rest and NSAIDs. Rest can often just be a modification of, or reduction in, the amount of activity being undertaken. For instance, the child with Osgood Schlatters syndrome may be perfectly able to undertake cycling or swimming but outdoor sports or running may need to be restricted until the apophysitis and architecture of the tibial tuberosity matures. For sportspeople, an adjustment of the training schedule to include shorter training sessions or to incorporate a variety of activities may be enough to allow the symptoms to settle. Most commonly this involves runners incorporating some gym or swimming sessions into their weekly routine.
Physiotherapy assessment of the biomechanics of the stance, gait and walking is important in the management of overuse injuries. Assessment of the flexibility of the spine, hips, iliotibial tract, hamstrings and extent of foot pronation is of primary importance.
Overuse injuries commonly result from a functional musculoskeletal imbalance or a slight anatomical deformity producing an inbalance. One example of this would be the development of pain or degeneration within the lateral aspect of the patello-femoral joint in patients with chronic patello-femoral subluxation (see figure 1, page 4). The most common would be spinal stiffness from a degenerative disc disease, hamstring tightness or pes planus (flat-foot) and foot pronation. Foot pronation should be assessed in the static, walking and also running position.
Many sportspeople begin to suffer problems as they age and their resilience, strength and flexibility slowly and inexorably diminish. This results in activities that they used to undertake without restriction becoming problematical as their soft tissue structures are no longer able to
withstand the stresses to which they are subjected.
Specific improvements in flexibility, strengthening and core stability are commonly helpful, as is consideration to the use of foot orthotics for sports. The use of correct orthotics can generally reduce the functional alignment of the foot and consequently the lower limbs, and often proves helpful. A podiatrist should be able to provide a range of custom-made orthotics.
The following are common overuse injuries of the knee:
• Runner's knee (Lateral epicondylitis)
• Jumper's knee (Patellar tendonitis)
• Osgood Schlatters disease (apophysitis of the tibial tuberosity)
• Sinding-Laarsen-Johannsen disease (apophysitis of the inferior pole of the patella)
• Quadriceps tendonitis
• Lateral patello-femoral hyperpressure
• Synovial plicae (residual embryonic synovial folds)
• Hamstring tendonitis.
Rest can be absolute for the management of fractures or infections when bed rest or use of a plaster cast may be needed. However, this is generally avoided wherever possible because of the detrimental effects on mobility, daily living, knee stiffness, muscle wasting and even articular degeneration. Wherever possible a degree of function and mobility is preserved by the use of crutches, partial weight bearing or a removable splint.
Often, particularly for overuse type of knee injuries or for competitive athletes or obsessive sportspeople, an alteration in their sporting activity or training schedule provides the rest needed for a condition to settle. This may be particularly appropriate for the runner or netball player with patellar tendonitis, the swimmer with plica syndrome, the golfer with a degenerative meniscus or the ageing soccer player with anterior cruciate ligament laxity.
This is the procedure of undertaking an arthroscopy and irrigating the joint to remove the synovial fluid and small pieces of floating debris from a degenerative knee. It can be undertaken in the office setting or under local anaesthetic.
Documented analysis has shown this procedure to be ineffective at relieving symptoms in most degenerative knees4,5 and, in short, the procedure is worthless. However, where a degenerative knee presents with an acute exacerbation of the symptoms or where those symptoms are mechanical, particularly where there is pain or tenderness along the joint lines, an arthroscopic washout can be worthwhile.
Another arthroscopic procedure known as ‘arthroscopic debridement' can be very successful. In this procedure the joint is irrigated and washed out, but in addition the removal of the degenerative torn meniscii, loose flaps of articular surface, loose bodies, osteophytes and localised synovectomy is undertaken. This often proves extremely beneficial, with complete recovery a possibility. The extent and longevity of the beneficial effect depends largely on the extent of underlying arthritis and degeneration of the weight-bearing articular surfaces.
In elderly patients, if most of the acute symptoms can be eradicated by an arthroscopic debridement and a joint replacement avoided for several years then, in many instances, this is preferable to an early joint replacement.
It is increasingly recognised that there is a significant incidence of acute damage to the articular cartilage in many knee injuries. The incidence of MRI demonstrable articular cartilage injuries (see figure 4, page 13) associated with ACL rupture has been put at 83 per cent6. The long-term success of treating many meniscal or ligamentous injuries to the knee is principally dependent on the degree of damage to the articular surfaces. In this respect it should be noted that where there has been a significant blow to the knee it is important to demonstrate the extent of any articular cartilage damage (see figure 5, above). In a knee with chronic instability, it should be well understood that with each episode of instability there is further damage to the articular surfaces and premature degeneration may result.
1 Jibuike OO, Paul-Taylor G, Maulvi S et al. Management of soft tissue knee injuries in an accident and emergency department: the effect of the introduction of a physiotherapy practitioner. Emerg Med J 2003;20(1):37–9
2 Ludman CN, Hough DO, Cooper TG et al. Silent meniscal abnormalities in athletes: magnetic resonance imaging of asymptomatic competitive gymnasts. Br J Sports Med 1999;33(6):414–6
3 Zanetti M, Pfirmann CW, Schmid MR et al. Clinical course of knees with asymptomatic meniscal abnormalities: findings at 2-year follow-up after MR imaging-based diagnosis. Radiology 2005;237(3):993–7
4 Bernard J, Lemon M, Patterson MH. Arthroscopic washout of the knee – a 5-year survival analysis. Knee 2004;11(3):233–5
5 Aichroth PM, Patel DV, Moyes ST. A prospective review of arthroscopic debridement for degenerative joint disease of the knee. Int Orthop 1991;15(4):351–5
6 Marks PH, Goldenberg JA, Vezina WC et al. Subchondral bone infractions in acute ligamentous knee injuries demonstrated on bone scintigraphy and magnetic resonance imaging. J Nucl Med 1992;33(4):516–20