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Management of the painful knee
ORTHOPAEDICS e IV: LOWER LIMB
Management of the painful knee
factors, associated symptoms such as paraesthesia or systemic symptoms, and whether there was a history of trauma. With trauma, it is key to distinguish the mechanism of injury, and whether there was a history of dislocation which required attention. It is also important to ascertain the presence of a knee effusion and the timing, over which this occurred, as well as establishing instability symptoms or locking. It is important to ascertain details of any previous surgery to the knee and if there is an implant in situ. If infection is suspected history must include questioning on systemic upset and possible sources of infections elsewhere in the body (i.e. urinary tract infection) that could have caused a bacteraemia with inoculation into the knee.
Nimesh G Patel Andrew D Toms Ben Waterson
Abstract The painful knee is one of the most common musculoskeletal presentations to primary and secondary care. It is important to distinguish between acute and chronic causes of knee pain, since the urgency of diagnosis and management can be vastly different. This short review covers the common diagnoses that are frequently encountered, with a systematic approach to confirming the diagnosis, and a management strategy.
Examination Examination of the knee should be targeted to the suspected pathology elicited from the history. The protocol follows the same principle as to other joints in the musculoskeletal system, which employs ‘look, feel, move and special tests’. Inspect the knee in the coronal and sagittal plane and observe for swelling or deformity and previous scars. Then to assess for inflammation by temperature, erythema and effusion. Here it is useful to compare both knees together. Examine the active and passive range of movement and patella tracking, then assess the joint line for tenderness. Specific to the knee is to test the ligaments systematically; this includes the ACL using Lachman’s test and anterior drawer. The PCL, using posterior sag sign and posterior draw test. The collateral ligaments should be tested in extension and 20 degrees of flexion. If the history is indicative of instability, then performing the dial test is useful to assess for a posterolateral corner injury. This is performed in the prone position. With both acute and chronic knee pain the examination should be completed by examination of the joint above and below, which involves hip and ankle examination to rule out referred pain.
Keywords Acute knee pain; anterior cruciate ligament; chronic knee pain; knee fracture; meniscus; painful knee; painful knee replacement
Introduction Painful knee is one of the most common presentations to both the primary and secondary care setting.1 The most common musculoskeletal tendinous and ligamentous injuries occur around the knee. It is therefore important to have a good understanding of the anatomy, aetiology and assessment of a painful knee in order to formulate a diagnosis and management plan in a timely manner. In the chronic setting osteoarthritis (OA) is common, with one-third of adults aged over 45 years seeking treatment for OA.2 A painful knee can present as either acute pain or be part of a more chronic painful condition. Here we will consider both, and discuss the aetiology of each type, and methods to diagnose and treat some of the important conditions. Table 1 outlines common differentials in both acute and chronic knee pain.
Infection The knee is the joint most commonly affected by septic arthritis. It is important to treat this in a timely manner, therefore suspicion and identification is vital. Irreversible cartilage damage can occur by 8 h due to the release of proteolytic enzymes from inflammatory cells.3 Septic arthritis is caused by pathogenic inoculation of microbes either directly or via haematogenous spread. This most common pathogen is Staphylococcus aureus, which accounts for more than 50% of cases.4
Acute knee pain History Assessment of the patient with an adequate history is key in the management of knee pain. It is important to ascertain the site and nature of the pain, the onset duration, exacerbating and relieving
Nimesh G Patel FRCS (Tr & Orth) is a Specialty Trainee Registrar at Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK. Conflicts of interest: none declared.
History and examination: Typically the patient will present with a painful and swollen joint with difficulty weight bearing. They may also have systemic manifestations of sepsis, with a fever of >38 C, and have symptoms of a potential primary infection elsewhere. The joint is generally irritable with a reduced range of movement, and is warm to touch. Though there could be erythema present, this is not common, and generally points towards bursitis or cellulitis as a diagnosis. It is important in the history to ascertain whether there has been any recent surgery to the knee, or whether the patient has had an arthroplasty on the affected side.
Andrew D Toms FRCS (Tr & Orth) is a Consultant Orthopaedic Surgeon at Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Exeter; and Honorary Clinical Professor at the College of Medicine, University of Exeter, UK. Conflicts of interest: none declared. Ben Waterson FRCS (Tr & Orth) is a Clinical Lecturer and Honorary Consultant at Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK. Conflicts of interest: none declared.
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Please cite this article as: Patel NG et al., Management of the painful knee, Surgery, https://doi.org/10.1016/j.mpsur.2019.12.009
ORTHOPAEDICS e IV: LOWER LIMB
the patient had been commenced on antibiotics prior to sampling).5 Importantly, a negative Gram stain does not exclude infection. Identification of crystals is important, as crystal arthropathy is the commonest differential to rule out, though it may coexist with infection.
Differential diagnosis in acute and chronic knee pain Acute pain
C C C C C
Acute or Chronic
C C C
Chronic pain
C C C
Infection e septic arthritis/osteomyelitis Fracture or tendon rupture Meniscal tear/bucket handle tear Cruciate ligament injury Patella instability Referred pain (spine/hip/ankle) Inflammatory arthropathy Crystal arthropathy Osteoarthritis Rheumatoid arthritis TKA failure
Management: Following aspiration, if septic the patient should be commenced on broad-spectrum IV antibiotics, then transition to organism specific therapy based on culture growth and advice from microbiology. Operative treatment is required with irrigation and debridement to reduce the infective load in the joint. This can be performed arthroscopically or via an open approach. The patient would need to be monitored for response with sequential blood inflammatory markers and will often require repeated debridement.
Table 1
Investigations: Blood markers for infection would be elevated, with a white cell count >10,000 cells/mL with left shift, erythrocyte sedimentation rate (ESR) >30 mm/h and C-reactive protein (CRP) >5 mg/L.5 In acute prosthetic joint infection a serum CRP >100 mg/L with a synovial WBC count >10,000 cells/mL is the threshold for an acute infection.6 Generally plain radiographs would be normal, but can sometimes indicate contiguous spread from adjacent osteomyelitis, or if performed after an interval could indicate joint destruction. Joint fluid aspiration is most useful and can direct antibiotic treatment if required. This must be done under aseptic conditions as demonstrated in Figure 1. With infection, findings include cloudy appearance of the fluid, white cell count >50,000 with neutrophil differential, and identification of an organism on Gram stain and culture (though this may not always be the case if
Trauma The presentation after trauma depends on the mechanism of injury. Knee pain can be caused by fracture to the tibia, femur or patella, ligament injury, meniscal injury, tendon rupture (quadriceps/patella), or dislocation of the patella or the knee joint itself. History and examination: The history should determine whether there was high or low velocity trauma with immediate pain and swelling and inability to weight bear. It is important to check for open wounds and perform and document a neurovascular assessment, paying attention to the common peroneal nerve e damage to which results in loss of sensation over the posterior knee and posterolateral calf and dorsum of the foot drop. Investigations: A plain radiograph usually will identify the location of the fracture and enable initial management. Occasionally the fracture is difficult to visualize on plain radiographs, and it is important to look for a lipohaemarthrosis on the lateral radiograph, which represents a fat/fluid line, indicating a likely fracture and requirement of further imaging (Figure 2). The most common fracture is of the tibial plateau, followed by the distal femur. Depending on the joint depression, congruity, or comminution, further information is required from a CT scan. This enables identification of subtle fractures as well as helps to plan for surgery if needed. Management: Initial management is to immobilize the joint using an extension knee splint or above knee backslab plaster to rest the soft tissue and help to manage pain. Specific fracture treatment will depend on the type of fracture. Intra-articular fractures where there is a joint depression or split will usually require open reduction and internal fixation using anatomic plates. In the case of a highly comminuted intra-articular fracture in an elderly patient with a background of knee pain and arthritis, performing a stemmed knee replacement is a better option, which allows expedited surgery and mobilization compared to fixation. Injuries with a congruent joint can be managed non-operatively and it is recommended to allow ROM through a hinged knee brace and protected weight bearing for 6 weeks. Interval radiographs will be required to monitor healing progress.
Figure 1 Aspiration of the knee.
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Please cite this article as: Patel NG et al., Management of the painful knee, Surgery, https://doi.org/10.1016/j.mpsur.2019.12.009
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Figure 2 Fat-fluid level of lipohaemarthrosis indicating a fracture.
are generally non-specific and difficult to elicit. McMurray’s test is the most commonly described, where a pop or click is palpated on the medial joint line when moving the knee into extension and external rotation from a flexed position, which correlates with a medial meniscus tear. This however is not very accurate.
Meniscus Meniscal injury is the most common indication for knee surgery. Medial meniscal tears are more common than lateral tears and both are more prevalent in ACL deficient knees.7 History and examination: Patients present with pain localizing to either the medial or lateral side of the joint, mechanical symptoms of ‘clicking or locking’ and commonly there is a history of a twisting injury. Swelling usually occurs several hours after the injury and this reflects the relatively poor vascular supply to the meniscus. The most sensitive and accurate physical examination finding is specific tenderness along the affected joint line. An effusion may also be present. Special provocative tests
Investigations: Since radiographs are usually normal, MRI scan is the gold standard to identify a meniscal tear (Figure 3). Management: Patients can initially be placed in a brace for comfort if required and allowed to mobilize as tolerated until outpatient review. In the case of a locked knee, urgent investigation with an MRI and then arthroscopic treatment is indicated.
Figure 3 T2 MRI sequence demonstrating medial meniscus tear.
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injury is commonly associated with lateral meniscal injury in up to 54% of cases.8 It can also be associated with a medial meniscus and medial collateral ligament injury in what is known as the ‘unhappy triad’. Examination can be difficult in the acute period due to effusion and pain. Specific tests include Lachman’s, which is graded by the amount of anterior tibial translation on the femur (grade 1 e3), anterior draw test, and pivot shift test. Investigations: It is useful to obtain plain radiographs in the context of immediate pain and swelling to the knee. This may reveal a Segond fracture, which is an avulsion fracture of the proximal lateral tibia, which commonly is associated with an ACL injury. This represents bony avulsion of the anterolateral complex of the knee.9 An MRI scan can be obtained on an acute outpatient basis, which will demonstrate the tear along with bone bruising (oedema) classically in the middle of the lateral femoral condyle and posterior one-third of the lateral tibial plateau9 (Figure 5).
Figure 4
Management: Initially, the patient can be managed in a knee brace and given crutches to aid mobility, with a view to rest and elevation while trying to improve range of motion as best as possible until outpatient review with an MRI scan. Focused rehabilitation should be commenced for all patients in the initial period. Those who cannot achieve dynamic stability can be considered for surgery. Meniscal surgery is usually carried out at the same sitting. Outcome and return to sport is largely dependent on motivation and compliance to the rehabilitation protocol, and is in the order of 9 months.
The mainstay for treatment for a degenerative meniscal tear is non-operative, and most symptoms settle down without further intervention. Persistent symptoms of a mechanical nature can be treated by a partial menisectomy if not amenable to repair. Whether to repair a meniscus or simply debride, it is determined by the location of the tear and its relation to the blood supply (Figure 4). Meniscal repair is indicated in peripheral redzone tears, especially in the context of a bucket handle tear and are most successful in combination with an ACL reconstruction since it performs as a secondary stabilizer. Success rates are improved in those patients under 40 years of age, with a normal lower limb alignment, a single tear and minimal arthritis. When performed in conjunction with an ACL reconstruction, success from meniscal repair is in the order of 70e95%.7 Meniscal transplant is an evolving technique in young patients with near total meniscectomies, but the long-term outcome is unclear in the literature.
Chronic knee pain Arthritis Osteoarthritis is secondary to progressive loss of articular cartilage and can be related to previous trauma, increased age, high BMI, and occupation that requires repetitive loading and bending although the most common relationship is probably genetic but little is known.
Anterior cruciate ligament History and examination: This is most crucial in identifying a possible ACL injury. The mechanism is typically a non-contact pivoting injury where the patient feels a ‘pop’ along with pain, followed by an immediate swelling from a haemarthrosis, due to rupture of the middle geniculate artery. They are usually not able to continue with that particular activity at the time. Acute ACL
History and examination: Patients present with functionlimiting knee pain with, stiffness, swelling, and pain at night or at rest. They may also complain of mechanical symptoms, or instability and deformity in severe cases.
Figure 5 T2 MRI sequences of ACL injury and associated bone bruising pattern.
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Figure 6 Radiographic features of osteoarthritis.
Examination findings include an effusion, with reduced range of movement with crepitus, joint tenderness and an antalgic gait. It is important to look for overall limb alignment and previous scars indicating surgery in the past.
Management: Patients will most commonly present in the primary care setting with onward referral if symptoms are severe enough to consider surgical treatment. Involvement of the multidisciplinary team is vital to offer the patient the correct treatment based on their expectations in a systematic approach. Non-operative treatment consists of counselling the patient and educating them about the condition and activity modification, a supervised exercise programme, weight loss (if BMI >25), and regular analgesia escalation based on the WHO analgesic ladder.10 If the patient fails non-operative treatment, surgery would be offered. The type of surgery is dependent on patient factors and the arthritis pattern on imaging and assessment.
Investigations: It is recommended to obtain weight-bearing radiographs of the knee in AP, lateral and skyline views. A long leg profile radiograph is useful, especially in the presence of deformity. Classical findings in osteoarthritis include a narrowed joint space, osteophytes, subchondral sclerosis and the presence of cysts (Figure 6). Occasionally an MRI scan is utilized to assess the cartilage surface in the three compartments when an isolated compartment is involved, in order to plan treatment.
Figure 7 Medial unicompartmental knee replacement.
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Figure 8 Radiographs of post cruciate retaining TKA with patella resurfacing.
In younger patients with single compartment disease, and deformity on alignment, an osteotomy can be offered to realign the mechanical axis and offload the affected compartment. Total knee arthroplasty (TKA) is the mainstay of surgical treatment for knee arthritis. This can be either with cruciate retaining or sacrificing implants, with largely similar outcomes. The patella is either routinely or selectively resurfaced, again with no recommendation (Figure 8). For isolated unicompartmental disease (usually the medial knee compartment), a unicompartmental knee arthroplasty is a desirable treatment option as it is associated with a faster recovery time in comparison to TKA (Figure 7).
On examination, check for pattern of gait, identifying any thrust from instability. Note surgical scars, erythema, increased temperature, effusion or sinuses, as well as tenderness along the joint line. Tenderness along the lateral patella border can indicate lateral facet syndrome due to an undersized patellar component. Tenderness on the medial or lateral aspect of the joint can be due to tibial component overhang or collateral ligament irritation, and posterolateral pain could be secondary to the popliteus tendon.12 Active and passive range of movement should be assessed and stability of the knee should be checked, along with patella tracking. Stability should be assessed in the coronal and sagittal planes in extension, 30 degrees flexion and 90 degrees of flexion.
Rheumatoid arthritis: A specific mention is required here as treatment must be in conjunction with a rheumatologist. The advent of modern biological medication to treat RA has seen the volume of patients presenting to the orthopaedic surgeon for surgery decline.11 Specific consideration around surgery is to address their medication peri-operatively, ensuring the patient understands the higher risk of wound related complications, and infection.
Investigations: Weight-bearing plain radiographs including long leg views as well as lateral and skyline views are useful in the assessment of the painful TKA. Serial radiographs can identify loosening, which is represented by radiolucent lines, change in component position or subsidence. Chronic infection may also produce resorption of bone at the interfaces, periosteal reaction, soft tissue swelling, and lysis. Serological investigations can be useful in identifying prosthetic joint infection. An ESR >30 has a sensitivity and specificity of 82% and 85%, respectively. C-reactive protein (CRP) value >10 has a sensitivity and specificity of 96% and 92%, respectively.13 This should be done along with aspiration of synovial fluid, performing a Gram stain, leucocyte count and culture. Studies have demonstrated that a fluid leucocyte count of >2500 cells/mm3 and >60% polymorphonuclear leukocytes has a sensitivity and specificity of over 95% in diagnosing infection.14 A SPECT CT scan can be useful to assess the prosthesis fixation and other causes of pain and can detect subtle stress fractures. A bone scan represents radionuclide uptake, which is influenced by blood flow and osteoclast activity. It has high sensitivity but low specificity. In a triple-phase scan (most commonly technetium99), increased uptake in the first and second phases represent hyperaemia and increased blood pool uptake respectively. A negative scan
Painful total knee arthroplasty Following TKA, some patients continue to have pain or develop a new pain, which may be accompanied by other symptoms such as instability, swelling or stiffness. Important causes are infection, instability, patellofemoral problems, osteolysis and prosthetic loosening.12 History and examination: Ascertain the main symptom experienced, and how it has changed over time. Pain can often be referred from the hip or the spine, but this may have been present prior to the TKA. Pain within the early postoperative period is normal but if disproportionate, may indicate acute infection, instability due to inadequate balancing, malalignment or impingement. Delayed onset pain is more likely to be due to loosening, polyethylene wear, late instability, chronic infection, or a stress fracture.
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is highly predictive of the absence of significant loosening or infection. Increased uptake in all three phases would be seen in infection, but also with polyethylene wear and loosening.
6 Parvizi J, Gehrke T, Chen AF. Proceedings of the International Consensus on periprosthetic joint infection. Bone Joint Lett J 2013; 95-B: 1450e2. https://doi.org/10.1302/0301-620X.95B11. 33135. 7 Beaufils P, Pujol N. Management of traumatic meniscal tear and degenerative meniscal lesions. Save the meniscus. Orthop Traumatol Surg Res 2017; 103: S237e44. https://doi.org/10.1016/j. otsr.2017.08.003. 8 Borchers JR, Kaeding CC, Pedroza AD, et al. Intra-articular findings in primary and revision anterior cruciate ligament reconstruction surgery. Am J Sports Med 2011; 39: 1889e93. https:// doi.org/10.1177/0363546511406871. 9 Yoon KH, Yoo JH, Kim K-I. Bone contusion and associated meniscal and medial collateral ligament injury in patients with anterior cruciate ligament rupture. J Bone Joint Surg Am 2011; 93: 1510e8. https://doi.org/10.2106/JBJS.J.01320. 10 Bennell KL, Hunter DJ, Hinman RS. Management of osteoarthritis of the knee. BMJ 2012; 345: e4934. https://doi.org/10.1136/bmj. e4934. 11 Lee JK, Choi C-H. Total knee arthroplasty in rheumatoid arthritis. Knee Surg Relat Res 2012; 24: 1e6. https://doi.org/10.5792/ksrr. 2012.24.1.1. 12 Mandalia V, Eyres K, Schranz P, Toms AD. Evaluation of patients with a painful total knee replacement. J Bone Joint Surg Br 2008; 90-B: 265e71. https://doi.org/10.1302/0301-620X.90B3.20140. 13 Greidanus NV, Masri BA, Garbuz DS, et al. Use of erythrocyte sedimentation rate and C-reactive protein level to diagnose infection before revision total knee arthroplasty. A prospective evaluation. J Bone Joint Surg 2007; 89: 1409. https://doi.org/10. 2106/JBJS.D.02602. 14 Bergin PF, Doppelt JD, Hamilton WG, et al. Detection of periprosthetic infections with use of ribosomal RNA-based polymerase chain reaction. J Bone Joint Surg Am 2010; 92: 654e63. https://doi.org/10.2106/JBJS.I.00400. 15 Toms AD, Mandalia V, Haigh R, Hopwood B. The management of patients with painful total knee replacement. J Bone Joint Surg Br 2009; 91-B: 143e50. https://doi.org/10.1302/0301-620X.91B2. 20995.
Management: This is obviously dependent on the vast array of causes of a painful TKA. It can stem from non-operative treatment with analgesia or a brace for stability, to operative options such as a manipulation for stiffness or to revision of the knee replacement. In the case of loosening, a single stage revision is carried out, usually with a stemmed prosthesis with variable degrees of constraint. If infection is the cause, a decision has to be made as to whether a single or two-staged revision is carried out, based on the causative organism, and chronicity of the infection.15
Summary The painful knee is a common presentation with a multitude of causes; therefore a systematic approach with a detailed history, good examination and appropriate investigations will aid in providing a diagnosis. Only then can a management plan be implemented. We have given an overview of some of the common painful knee conditions that present both acutely and on a chronic basis - there are less common conditions that are beyond the scope of this article. A REFERENCES 1 British Medical Journal, British Medical Journal. BMJBest Practices. BMJ Publ. Group https://bestpractice.bmj.com/topics/engb/575. (accessed 13 Mar 2019). 2 Arthritis Research UK. Arthritis Research UK. https://www. arthritisresearchuk.org/. (accessed 29 Mar 2019). 3 Johns BP, Loewenthal MR, Dewar DC. Open compared with arthroscopic treatment of acute septic arthritis of the native knee. J Bone Joint Surg 2017; 99: 499e505. https://doi.org/10.2106/ JBJS.16.00110. 4 Shirtliff ME, Mader JT. Acute septic arthritis. Clin Microbiol Rev 2002; 15: 527e44. https://doi.org/10.1128/CMR.15.4.527-544.2002. 5 Carpenter CR, Schuur JD, Everett WW, Pines JM. Evidencebased diagnostics: adult septic arthritis. Acad Emerg Med 2011; 18: 781e96. https://doi.org/10.1111/j.1553-2712.2011.01121.x.
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Please cite this article as: Patel NG et al., Management of the painful knee, Surgery, https://doi.org/10.1016/j.mpsur.2019.12.009
Management of the painful knee
factors, associated symptoms such as paraesthesia or systemic symptoms, and whether there was a history of trauma. With trauma, it is key to distinguish the mechanism of injury, and whether there was a history of dislocation which required attention. It is also important to ascertain the presence of a knee effusion and the timing, over which this occurred, as well as establishing instability symptoms or locking. It is important to ascertain details of any previous surgery to the knee and if there is an implant in situ. If infection is suspected history must include questioning on systemic upset and possible sources of infections elsewhere in the body (i.e. urinary tract infection) that could have caused a bacteraemia with inoculation into the knee.
Nimesh G Patel Andrew D Toms Ben Waterson
Abstract The painful knee is one of the most common musculoskeletal presentations to primary and secondary care. It is important to distinguish between acute and chronic causes of knee pain, since the urgency of diagnosis and management can be vastly different. This short review covers the common diagnoses that are frequently encountered, with a systematic approach to confirming the diagnosis, and a management strategy.
Examination Examination of the knee should be targeted to the suspected pathology elicited from the history. The protocol follows the same principle as to other joints in the musculoskeletal system, which employs ‘look, feel, move and special tests’. Inspect the knee in the coronal and sagittal plane and observe for swelling or deformity and previous scars. Then to assess for inflammation by temperature, erythema and effusion. Here it is useful to compare both knees together. Examine the active and passive range of movement and patella tracking, then assess the joint line for tenderness. Specific to the knee is to test the ligaments systematically; this includes the ACL using Lachman’s test and anterior drawer. The PCL, using posterior sag sign and posterior draw test. The collateral ligaments should be tested in extension and 20 degrees of flexion. If the history is indicative of instability, then performing the dial test is useful to assess for a posterolateral corner injury. This is performed in the prone position. With both acute and chronic knee pain the examination should be completed by examination of the joint above and below, which involves hip and ankle examination to rule out referred pain.
Keywords Acute knee pain; anterior cruciate ligament; chronic knee pain; knee fracture; meniscus; painful knee; painful knee replacement
Introduction Painful knee is one of the most common presentations to both the primary and secondary care setting.1 The most common musculoskeletal tendinous and ligamentous injuries occur around the knee. It is therefore important to have a good understanding of the anatomy, aetiology and assessment of a painful knee in order to formulate a diagnosis and management plan in a timely manner. In the chronic setting osteoarthritis (OA) is common, with one-third of adults aged over 45 years seeking treatment for OA.2 A painful knee can present as either acute pain or be part of a more chronic painful condition. Here we will consider both, and discuss the aetiology of each type, and methods to diagnose and treat some of the important conditions. Table 1 outlines common differentials in both acute and chronic knee pain.
Infection The knee is the joint most commonly affected by septic arthritis. It is important to treat this in a timely manner, therefore suspicion and identification is vital. Irreversible cartilage damage can occur by 8 h due to the release of proteolytic enzymes from inflammatory cells.3 Septic arthritis is caused by pathogenic inoculation of microbes either directly or via haematogenous spread. This most common pathogen is Staphylococcus aureus, which accounts for more than 50% of cases.4
Acute knee pain History Assessment of the patient with an adequate history is key in the management of knee pain. It is important to ascertain the site and nature of the pain, the onset duration, exacerbating and relieving
Nimesh G Patel FRCS (Tr & Orth) is a Specialty Trainee Registrar at Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK. Conflicts of interest: none declared.
History and examination: Typically the patient will present with a painful and swollen joint with difficulty weight bearing. They may also have systemic manifestations of sepsis, with a fever of >38 C, and have symptoms of a potential primary infection elsewhere. The joint is generally irritable with a reduced range of movement, and is warm to touch. Though there could be erythema present, this is not common, and generally points towards bursitis or cellulitis as a diagnosis. It is important in the history to ascertain whether there has been any recent surgery to the knee, or whether the patient has had an arthroplasty on the affected side.
Andrew D Toms FRCS (Tr & Orth) is a Consultant Orthopaedic Surgeon at Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Exeter; and Honorary Clinical Professor at the College of Medicine, University of Exeter, UK. Conflicts of interest: none declared. Ben Waterson FRCS (Tr & Orth) is a Clinical Lecturer and Honorary Consultant at Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK. Conflicts of interest: none declared.
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Please cite this article as: Patel NG et al., Management of the painful knee, Surgery, https://doi.org/10.1016/j.mpsur.2019.12.009
ORTHOPAEDICS e IV: LOWER LIMB
the patient had been commenced on antibiotics prior to sampling).5 Importantly, a negative Gram stain does not exclude infection. Identification of crystals is important, as crystal arthropathy is the commonest differential to rule out, though it may coexist with infection.
Differential diagnosis in acute and chronic knee pain Acute pain
C C C C C
Acute or Chronic
C C C
Chronic pain
C C C
Infection e septic arthritis/osteomyelitis Fracture or tendon rupture Meniscal tear/bucket handle tear Cruciate ligament injury Patella instability Referred pain (spine/hip/ankle) Inflammatory arthropathy Crystal arthropathy Osteoarthritis Rheumatoid arthritis TKA failure
Management: Following aspiration, if septic the patient should be commenced on broad-spectrum IV antibiotics, then transition to organism specific therapy based on culture growth and advice from microbiology. Operative treatment is required with irrigation and debridement to reduce the infective load in the joint. This can be performed arthroscopically or via an open approach. The patient would need to be monitored for response with sequential blood inflammatory markers and will often require repeated debridement.
Table 1
Investigations: Blood markers for infection would be elevated, with a white cell count >10,000 cells/mL with left shift, erythrocyte sedimentation rate (ESR) >30 mm/h and C-reactive protein (CRP) >5 mg/L.5 In acute prosthetic joint infection a serum CRP >100 mg/L with a synovial WBC count >10,000 cells/mL is the threshold for an acute infection.6 Generally plain radiographs would be normal, but can sometimes indicate contiguous spread from adjacent osteomyelitis, or if performed after an interval could indicate joint destruction. Joint fluid aspiration is most useful and can direct antibiotic treatment if required. This must be done under aseptic conditions as demonstrated in Figure 1. With infection, findings include cloudy appearance of the fluid, white cell count >50,000 with neutrophil differential, and identification of an organism on Gram stain and culture (though this may not always be the case if
Trauma The presentation after trauma depends on the mechanism of injury. Knee pain can be caused by fracture to the tibia, femur or patella, ligament injury, meniscal injury, tendon rupture (quadriceps/patella), or dislocation of the patella or the knee joint itself. History and examination: The history should determine whether there was high or low velocity trauma with immediate pain and swelling and inability to weight bear. It is important to check for open wounds and perform and document a neurovascular assessment, paying attention to the common peroneal nerve e damage to which results in loss of sensation over the posterior knee and posterolateral calf and dorsum of the foot drop. Investigations: A plain radiograph usually will identify the location of the fracture and enable initial management. Occasionally the fracture is difficult to visualize on plain radiographs, and it is important to look for a lipohaemarthrosis on the lateral radiograph, which represents a fat/fluid line, indicating a likely fracture and requirement of further imaging (Figure 2). The most common fracture is of the tibial plateau, followed by the distal femur. Depending on the joint depression, congruity, or comminution, further information is required from a CT scan. This enables identification of subtle fractures as well as helps to plan for surgery if needed. Management: Initial management is to immobilize the joint using an extension knee splint or above knee backslab plaster to rest the soft tissue and help to manage pain. Specific fracture treatment will depend on the type of fracture. Intra-articular fractures where there is a joint depression or split will usually require open reduction and internal fixation using anatomic plates. In the case of a highly comminuted intra-articular fracture in an elderly patient with a background of knee pain and arthritis, performing a stemmed knee replacement is a better option, which allows expedited surgery and mobilization compared to fixation. Injuries with a congruent joint can be managed non-operatively and it is recommended to allow ROM through a hinged knee brace and protected weight bearing for 6 weeks. Interval radiographs will be required to monitor healing progress.
Figure 1 Aspiration of the knee.
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Figure 2 Fat-fluid level of lipohaemarthrosis indicating a fracture.
are generally non-specific and difficult to elicit. McMurray’s test is the most commonly described, where a pop or click is palpated on the medial joint line when moving the knee into extension and external rotation from a flexed position, which correlates with a medial meniscus tear. This however is not very accurate.
Meniscus Meniscal injury is the most common indication for knee surgery. Medial meniscal tears are more common than lateral tears and both are more prevalent in ACL deficient knees.7 History and examination: Patients present with pain localizing to either the medial or lateral side of the joint, mechanical symptoms of ‘clicking or locking’ and commonly there is a history of a twisting injury. Swelling usually occurs several hours after the injury and this reflects the relatively poor vascular supply to the meniscus. The most sensitive and accurate physical examination finding is specific tenderness along the affected joint line. An effusion may also be present. Special provocative tests
Investigations: Since radiographs are usually normal, MRI scan is the gold standard to identify a meniscal tear (Figure 3). Management: Patients can initially be placed in a brace for comfort if required and allowed to mobilize as tolerated until outpatient review. In the case of a locked knee, urgent investigation with an MRI and then arthroscopic treatment is indicated.
Figure 3 T2 MRI sequence demonstrating medial meniscus tear.
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injury is commonly associated with lateral meniscal injury in up to 54% of cases.8 It can also be associated with a medial meniscus and medial collateral ligament injury in what is known as the ‘unhappy triad’. Examination can be difficult in the acute period due to effusion and pain. Specific tests include Lachman’s, which is graded by the amount of anterior tibial translation on the femur (grade 1 e3), anterior draw test, and pivot shift test. Investigations: It is useful to obtain plain radiographs in the context of immediate pain and swelling to the knee. This may reveal a Segond fracture, which is an avulsion fracture of the proximal lateral tibia, which commonly is associated with an ACL injury. This represents bony avulsion of the anterolateral complex of the knee.9 An MRI scan can be obtained on an acute outpatient basis, which will demonstrate the tear along with bone bruising (oedema) classically in the middle of the lateral femoral condyle and posterior one-third of the lateral tibial plateau9 (Figure 5).
Figure 4
Management: Initially, the patient can be managed in a knee brace and given crutches to aid mobility, with a view to rest and elevation while trying to improve range of motion as best as possible until outpatient review with an MRI scan. Focused rehabilitation should be commenced for all patients in the initial period. Those who cannot achieve dynamic stability can be considered for surgery. Meniscal surgery is usually carried out at the same sitting. Outcome and return to sport is largely dependent on motivation and compliance to the rehabilitation protocol, and is in the order of 9 months.
The mainstay for treatment for a degenerative meniscal tear is non-operative, and most symptoms settle down without further intervention. Persistent symptoms of a mechanical nature can be treated by a partial menisectomy if not amenable to repair. Whether to repair a meniscus or simply debride, it is determined by the location of the tear and its relation to the blood supply (Figure 4). Meniscal repair is indicated in peripheral redzone tears, especially in the context of a bucket handle tear and are most successful in combination with an ACL reconstruction since it performs as a secondary stabilizer. Success rates are improved in those patients under 40 years of age, with a normal lower limb alignment, a single tear and minimal arthritis. When performed in conjunction with an ACL reconstruction, success from meniscal repair is in the order of 70e95%.7 Meniscal transplant is an evolving technique in young patients with near total meniscectomies, but the long-term outcome is unclear in the literature.
Chronic knee pain Arthritis Osteoarthritis is secondary to progressive loss of articular cartilage and can be related to previous trauma, increased age, high BMI, and occupation that requires repetitive loading and bending although the most common relationship is probably genetic but little is known.
Anterior cruciate ligament History and examination: This is most crucial in identifying a possible ACL injury. The mechanism is typically a non-contact pivoting injury where the patient feels a ‘pop’ along with pain, followed by an immediate swelling from a haemarthrosis, due to rupture of the middle geniculate artery. They are usually not able to continue with that particular activity at the time. Acute ACL
History and examination: Patients present with functionlimiting knee pain with, stiffness, swelling, and pain at night or at rest. They may also complain of mechanical symptoms, or instability and deformity in severe cases.
Figure 5 T2 MRI sequences of ACL injury and associated bone bruising pattern.
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Figure 6 Radiographic features of osteoarthritis.
Examination findings include an effusion, with reduced range of movement with crepitus, joint tenderness and an antalgic gait. It is important to look for overall limb alignment and previous scars indicating surgery in the past.
Management: Patients will most commonly present in the primary care setting with onward referral if symptoms are severe enough to consider surgical treatment. Involvement of the multidisciplinary team is vital to offer the patient the correct treatment based on their expectations in a systematic approach. Non-operative treatment consists of counselling the patient and educating them about the condition and activity modification, a supervised exercise programme, weight loss (if BMI >25), and regular analgesia escalation based on the WHO analgesic ladder.10 If the patient fails non-operative treatment, surgery would be offered. The type of surgery is dependent on patient factors and the arthritis pattern on imaging and assessment.
Investigations: It is recommended to obtain weight-bearing radiographs of the knee in AP, lateral and skyline views. A long leg profile radiograph is useful, especially in the presence of deformity. Classical findings in osteoarthritis include a narrowed joint space, osteophytes, subchondral sclerosis and the presence of cysts (Figure 6). Occasionally an MRI scan is utilized to assess the cartilage surface in the three compartments when an isolated compartment is involved, in order to plan treatment.
Figure 7 Medial unicompartmental knee replacement.
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Figure 8 Radiographs of post cruciate retaining TKA with patella resurfacing.
In younger patients with single compartment disease, and deformity on alignment, an osteotomy can be offered to realign the mechanical axis and offload the affected compartment. Total knee arthroplasty (TKA) is the mainstay of surgical treatment for knee arthritis. This can be either with cruciate retaining or sacrificing implants, with largely similar outcomes. The patella is either routinely or selectively resurfaced, again with no recommendation (Figure 8). For isolated unicompartmental disease (usually the medial knee compartment), a unicompartmental knee arthroplasty is a desirable treatment option as it is associated with a faster recovery time in comparison to TKA (Figure 7).
On examination, check for pattern of gait, identifying any thrust from instability. Note surgical scars, erythema, increased temperature, effusion or sinuses, as well as tenderness along the joint line. Tenderness along the lateral patella border can indicate lateral facet syndrome due to an undersized patellar component. Tenderness on the medial or lateral aspect of the joint can be due to tibial component overhang or collateral ligament irritation, and posterolateral pain could be secondary to the popliteus tendon.12 Active and passive range of movement should be assessed and stability of the knee should be checked, along with patella tracking. Stability should be assessed in the coronal and sagittal planes in extension, 30 degrees flexion and 90 degrees of flexion.
Rheumatoid arthritis: A specific mention is required here as treatment must be in conjunction with a rheumatologist. The advent of modern biological medication to treat RA has seen the volume of patients presenting to the orthopaedic surgeon for surgery decline.11 Specific consideration around surgery is to address their medication peri-operatively, ensuring the patient understands the higher risk of wound related complications, and infection.
Investigations: Weight-bearing plain radiographs including long leg views as well as lateral and skyline views are useful in the assessment of the painful TKA. Serial radiographs can identify loosening, which is represented by radiolucent lines, change in component position or subsidence. Chronic infection may also produce resorption of bone at the interfaces, periosteal reaction, soft tissue swelling, and lysis. Serological investigations can be useful in identifying prosthetic joint infection. An ESR >30 has a sensitivity and specificity of 82% and 85%, respectively. C-reactive protein (CRP) value >10 has a sensitivity and specificity of 96% and 92%, respectively.13 This should be done along with aspiration of synovial fluid, performing a Gram stain, leucocyte count and culture. Studies have demonstrated that a fluid leucocyte count of >2500 cells/mm3 and >60% polymorphonuclear leukocytes has a sensitivity and specificity of over 95% in diagnosing infection.14 A SPECT CT scan can be useful to assess the prosthesis fixation and other causes of pain and can detect subtle stress fractures. A bone scan represents radionuclide uptake, which is influenced by blood flow and osteoclast activity. It has high sensitivity but low specificity. In a triple-phase scan (most commonly technetium99), increased uptake in the first and second phases represent hyperaemia and increased blood pool uptake respectively. A negative scan
Painful total knee arthroplasty Following TKA, some patients continue to have pain or develop a new pain, which may be accompanied by other symptoms such as instability, swelling or stiffness. Important causes are infection, instability, patellofemoral problems, osteolysis and prosthetic loosening.12 History and examination: Ascertain the main symptom experienced, and how it has changed over time. Pain can often be referred from the hip or the spine, but this may have been present prior to the TKA. Pain within the early postoperative period is normal but if disproportionate, may indicate acute infection, instability due to inadequate balancing, malalignment or impingement. Delayed onset pain is more likely to be due to loosening, polyethylene wear, late instability, chronic infection, or a stress fracture.
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is highly predictive of the absence of significant loosening or infection. Increased uptake in all three phases would be seen in infection, but also with polyethylene wear and loosening.
6 Parvizi J, Gehrke T, Chen AF. Proceedings of the International Consensus on periprosthetic joint infection. Bone Joint Lett J 2013; 95-B: 1450e2. https://doi.org/10.1302/0301-620X.95B11. 33135. 7 Beaufils P, Pujol N. Management of traumatic meniscal tear and degenerative meniscal lesions. Save the meniscus. Orthop Traumatol Surg Res 2017; 103: S237e44. https://doi.org/10.1016/j. otsr.2017.08.003. 8 Borchers JR, Kaeding CC, Pedroza AD, et al. Intra-articular findings in primary and revision anterior cruciate ligament reconstruction surgery. Am J Sports Med 2011; 39: 1889e93. https:// doi.org/10.1177/0363546511406871. 9 Yoon KH, Yoo JH, Kim K-I. Bone contusion and associated meniscal and medial collateral ligament injury in patients with anterior cruciate ligament rupture. J Bone Joint Surg Am 2011; 93: 1510e8. https://doi.org/10.2106/JBJS.J.01320. 10 Bennell KL, Hunter DJ, Hinman RS. Management of osteoarthritis of the knee. BMJ 2012; 345: e4934. https://doi.org/10.1136/bmj. e4934. 11 Lee JK, Choi C-H. Total knee arthroplasty in rheumatoid arthritis. Knee Surg Relat Res 2012; 24: 1e6. https://doi.org/10.5792/ksrr. 2012.24.1.1. 12 Mandalia V, Eyres K, Schranz P, Toms AD. Evaluation of patients with a painful total knee replacement. J Bone Joint Surg Br 2008; 90-B: 265e71. https://doi.org/10.1302/0301-620X.90B3.20140. 13 Greidanus NV, Masri BA, Garbuz DS, et al. Use of erythrocyte sedimentation rate and C-reactive protein level to diagnose infection before revision total knee arthroplasty. A prospective evaluation. J Bone Joint Surg 2007; 89: 1409. https://doi.org/10. 2106/JBJS.D.02602. 14 Bergin PF, Doppelt JD, Hamilton WG, et al. Detection of periprosthetic infections with use of ribosomal RNA-based polymerase chain reaction. J Bone Joint Surg Am 2010; 92: 654e63. https://doi.org/10.2106/JBJS.I.00400. 15 Toms AD, Mandalia V, Haigh R, Hopwood B. The management of patients with painful total knee replacement. J Bone Joint Surg Br 2009; 91-B: 143e50. https://doi.org/10.1302/0301-620X.91B2. 20995.
Management: This is obviously dependent on the vast array of causes of a painful TKA. It can stem from non-operative treatment with analgesia or a brace for stability, to operative options such as a manipulation for stiffness or to revision of the knee replacement. In the case of loosening, a single stage revision is carried out, usually with a stemmed prosthesis with variable degrees of constraint. If infection is the cause, a decision has to be made as to whether a single or two-staged revision is carried out, based on the causative organism, and chronicity of the infection.15
Summary The painful knee is a common presentation with a multitude of causes; therefore a systematic approach with a detailed history, good examination and appropriate investigations will aid in providing a diagnosis. Only then can a management plan be implemented. We have given an overview of some of the common painful knee conditions that present both acutely and on a chronic basis - there are less common conditions that are beyond the scope of this article. A REFERENCES 1 British Medical Journal, British Medical Journal. BMJBest Practices. BMJ Publ. Group https://bestpractice.bmj.com/topics/engb/575. (accessed 13 Mar 2019). 2 Arthritis Research UK. Arthritis Research UK. https://www. arthritisresearchuk.org/. (accessed 29 Mar 2019). 3 Johns BP, Loewenthal MR, Dewar DC. Open compared with arthroscopic treatment of acute septic arthritis of the native knee. J Bone Joint Surg 2017; 99: 499e505. https://doi.org/10.2106/ JBJS.16.00110. 4 Shirtliff ME, Mader JT. Acute septic arthritis. Clin Microbiol Rev 2002; 15: 527e44. https://doi.org/10.1128/CMR.15.4.527-544.2002. 5 Carpenter CR, Schuur JD, Everett WW, Pines JM. Evidencebased diagnostics: adult septic arthritis. Acad Emerg Med 2011; 18: 781e96. https://doi.org/10.1111/j.1553-2712.2011.01121.x.
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