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Viêm khớp nhiễm trùng ở đầu gối

Updated Sep 2026
Illustration: knee

Trang này được dịch bằng máy và chưa được bác sĩ kiểm tra. Bản tiếng Anh là bản chính thức.

Những triệu chứng bạn đang gặp phải

Trong trường hợp viêm khớp nhiễm trùng ở đầu gối, chính khớp gối bị nhiễm khuẩn. Khớp gối thường nóng, sưng và rất đau khi chạm vào. Cơn đau xuất hiện sâu bên trong khớp; thông thường cơn đau dữ dội đến mức bạn không thể chịu được trọng lượng cơ thể lên chân đó. Bạn cũng có thể bị sốt.

Khác với viêm khớp do thoái hóa, cơn đau này không xuất hiện và biến mất tùy theo hoạt động. Cơn đau luôn tồn tại, và việc cử động khớp gối hoặc đứng lên chân đó sẽ khiến đau tăng lên. Nhiều người hoàn toàn không thể chịu được trọng lượng cơ thể; vì vậy việc đi vệ sinh hay ra xe hơi trở thành điều bất khả thi nếu không có sự trợ giúp. Việc gập đầu gối để ngồi xuống, lên xe hoặc đi giày cũng thường gây đau đớn dữ dội.

Tình trạng sưng có thể xuất hiện nhanh chóng, chỉ trong vài giờ hoặc một, hai ngày. Khớp gối có thể trông phù nề và cảm giác nóng hơn so với khớp gối còn lại. Vào ban đêm, tình trạng này càng khó chịu vì cơn đau nhức liên tục khiến bạn không ngủ được; ngay cả việc cử động nhẹ dưới chăn cũng gây đau nhói.

Nếu bạn đã từng phẫu thuật thay khớp gối hoặc phẫu thuật liên quan đến khớp gối như tái tạo dây chằng chéo trước (ACL), hãy chú ý đến bất kỳ cơn đau, sưng hay sốt mới nào xuất hiện ở khớp đó. Viêm nhiễm sau phẫu thuật tái tạo ACL rất hiếm gặp, nhưng vẫn cần được xử lý ngay lập tức. Điều tương tự cũng áp dụng với những người mắc bệnh như bệnh máu khó đông: khớp gối sưng, nóng và đau có thể do chảy máu vào khớp chứ không phải do nhiễm trùng. Nếu việc điều trị chảy máu không mang lại hiệu quả nhanh chóng, cần kiểm tra xem có nhiễm trùng hay không.

Tình trạng này là một cấp cứu ngoại khoa. Nếu đầu gối của bạn nóng, sưng, đau kèm sốt và không thể chịu được trọng lượng cơ thể lên chân đó, cần được thăm khám ngay lập tức. Xét nghiệm quan trọng nhất là chọc hút dịch khớp bằng kim tiêm; thủ thuật này vừa giúp xác nhận chẩn đoán vừa bắt đầu quá trình điều trị. Các xét nghiệm máu và chẩn đoán hình ảnh như chụp MRI cũng giúp bổ sung thông tin cần thiết.

Chuyện gì đang xảy ra thực sự

Khớp gối vốn là một khoang kín. Hai đầu xương đùi và xương chày gặp nhau bên trong khoang này; một lớp dịch bôi trơn mỏng giúp chúng trượt nhẹ nhàng. Trong trường hợp viêm khớp nhiễm trùng, vi khuẩn đã xâm nhập vào khoang kín này và sinh sôi nảy nở trong dịch khớp.

Những vi khuẩn này, thường là vi khuẩn Staphylococcus aureus – loại vi khuẩn phổ biến trên da – gây ra phản ứng viêm dữ dội. Lớp màng bao quanh khớp tiết ra thêm nhiều dịch như một phần cơ chế phòng vệ của cơ thể; vì vậy khớp gối sưng lên rất nhanh. Lượng dịch bị giữ lại tạo ra áp lực bên trong khớp; chính áp lực này gây ra cơn đau sâu, nhói theo nhịp đập cùng cảm giác nóng mà bạn cảm nhận được. Tình trạng sưng viêm còn khiến khớp không thể cử động, vì vậy việc gập gối hoặc chịu trọng lượng lên khớp gần như không thể thực hiện được.

Nếu không được điều trị, nhiễm trùng sẽ không dừng lại. Vi khuẩn cùng phản ứng viêm mà chúng gây ra dần làm tổn thương lớp sụn mịn phủ lên đầu xương bên trong khớp. Những tổn thương này có thể trở thành vĩnh viễn; vì thế tình trạng này được xem là một cấp cứu ngoại khoa chứ không thể chờ đợi bằng thuốc đơn thuần.

Quá trình tương tự cũng có thể xảy ra ở những khớp gối đã từng được phẫu thuật. Sau các ca phẫu thuật như tái tạo dây chằng chéo trước (ACL) hoặc thay khớp gối, đôi khi vi khuẩn vẫn có thể xâm nhập vào khớp và gây phản ứng sưng nóng tương tự. Nếu bạn từng bị viêm khớp nhiễm trùng ở một khớp gối, khả năng nhiễm trùng tái phát khi tiến hành thay khớp gối sau này cũng cao hơn so với những khớp chưa từng bị nhiễm trùng.

Mục tiêu của điều trị là rút hết dịch nhiễm trùng ra, làm sạch khớp và dùng kháng sinh để tiêu diệt những vi khuẩn còn sót lại. Việc rút dịch nhanh chóng giúp giảm áp lực, bảo vệ lớp sụn khỏi những tổn thương lâu dài.

Những gì chúng tôi có thể làm

Vì đây là tình trạng nhiễm trùng xảy ra bên trong một khớp kín, nên không có giai đoạn tự điều trị nào có thể thử trước. Việc nghỉ ngơi, dùng thuốc hoặc vật lý trị liệu đều không thể chữa khỏi bệnh; việc chần chừ sẽ khiến vi khuẩn phá hủy sụn khớp. Bước đầu tiên là chọc hút dịch khớp bằng kim tiêm, nhằm giảm áp lực và lấy mẫu để xét nghiệm. Ngay sau đó, chúng tôi bắt đầu điều trị bằng kháng sinh nhắm vào loại vi khuẩn được phát hiện trong mẫu đó.

Hầu hết các trường hợp viêm khớp gối đều cần can thiệp nhiều hơn việc chọc hút bằng kim. Chúng tôi sẽ rửa sạch khớp, bằng phương pháp nội soi khớp (arthroscopy) hoặc mổ mở để rửa khớp (arthrotomy). Phương pháp nội soi sử dụng những vết mổ nhỏ và camera, giúp quan sát những vùng khớp mà phương pháp mổ mở không thể tiếp cận. Phương pháp này cũng thường gây ít đau đớn hơn sau phẫu thuật, giúp bệnh nhân sớm vận động khớp gối trở lại. Nhiều ca nhiễm trùng khỏi hẳn sau một lần rửa khớp. Nếu nhiễm trùng tái phát, chúng tôi có thể loại bỏ thêm mô màng khớp bị viêm trong một ca nội soi tiếp theo.

Trong trường hợp bệnh nhân đã từng phẫu thuật tái tạo dây chằng chéo trước (ACL) mà khớp gối bị nhiễm trùng, phẫu thuật vẫn là phương pháp điều trị chính. Việc rửa sạch khớp kết hợp với kháng sinh có thể chữa khỏi nhiễm trùng và bảo tồn mảnh ghép. Nếu nhiễm trùng vẫn không thuyên giảm, việc loại bỏ mảnh ghép cùng các dụng cụ cố định thường giúp kiểm soát được tình trạng này.

Khi nhiễm trùng đã hết, mục tiêu điều trị là giúp khớp gối phục hồi khả năng vận động. Vật lý trị liệu giúp bệnh nhân tái tạo vận động và sức mạnh cơ; hầu hết mọi người đều có thể tập gập và duỗi thẳng khớp gối mà không cần phẫu thuật thêm.

Có hai trường hợp cần cân nhắc thay khớp gối. Nếu khớp gối vừa bị nhiễm trùng hoặc đang trong giai đoạn nhiễm trùng, việc thay khớp chưa thể thực hiện vì khớp mới cũng có nguy cơ bị nhiễm trùng. Sau khi nhiễm trùng đã hoàn toàn khỏi, việc thay khớp mới được xem xét. Trong các trường hợp này, tỷ lệ khỏi bệnh là 87% nếu nhiễm trùng vẫn còn hoạt động và 95% nếu nhiễm trùng đã ổn định trước khi phẫu thuật. Nếu khớp gối đã được thay mà vẫn bị nhiễm trùng và không thể chữa khỏi, phương pháp cuối cùng là hàn cứng khớp gối (arthrodesis). Phương pháp này tạo ra một khớp gối ổn định, không đau nhưng không thể gập được; nó chỉ được áp dụng khi không còn cách nào khác.

Những điều có thể xảy ra

Nếu được điều trị kịp thời, hầu hết các trường hợp nhiễm trùng đều có thể khỏi và khớp gối vẫn được giữ lại. Cơn đau dữ dội và tình trạng sưng thường giảm đi sau khi khớp gối được rút dịch và rửa sạch; tuy nhiên, khớp gối thường vẫn cứng và yếu trong nhiều tuần liền cho đến khi bệnh nhân phục hồi vận động và sức mạnh nhờ vật lý trị liệu. Một số người có thể đi lại được chỉ vài ngày sau khi rửa khớp, trong khi những người khác cần thời gian lâu hơn; không có lịch trình cụ thể nào phù hợp với tất cả mọi người.

Tiên lượng phụ thuộc rất nhiều vào tốc độ điều trị nhiễm trùng. Vi khuẩn càng ở trong khớp lâu thì càng gây tổn thương sụn nhiều hơn, và những tổn thương này không thể phục hồi được. Nếu được điều trị sớm, nhiều khớp gối có thể trở lại trạng thái hoạt động bình thường. Ngược lại, nếu không được điều trị, nhiễm trùng sẽ tiếp tục gây hại cho khớp, dẫn đến tình trạng cứng khớp và đau đớn lâu dài.

Một số trường hợp nhiễm trùng không khỏi sau lần rửa khớp đầu tiên. Nếu các dấu hiệu nhiễm trùng tái phát sau điều trị, điều đó có thể nghĩa là vi khuẩn đã lan sang xương xung quanh khớp; tình trạng này khó điều trị hơn và cần phẫu thuật thêm. Có thể cần phải rửa khớp nhiều lần, dùng kháng sinh trong thời gian dài hoặc thực hiện các thủ thuật khác trước khi nhiễm trùng hoàn toàn biến mất.

Nếu bạn đã từng phẫu thuật tái tạo dây chằng chéo trước (ACL) và khớp gối bị nhiễm trùng, phẫu thuật là phương pháp tốt nhất để loại bỏ nhiễm trùng và bảo tồn mảnh ghép. Việc chần chừ hoặc cố gắng điều trị mà không phẫu thuật thường dẫn đến thời gian hồi phục kéo dài và kết quả điều trị kém hơn. Nếu được điều trị đúng cách, nhiều người có thể phục hồi chức năng khớp gối tương đương với mức họ có được nếu không bị nhiễm trùng.

Trong trường hợp khớp gối đã được thay khớp nhân tạo mà vẫn bị nhiễm trùng không thể chữa khỏi, cần phải phẫu thuật thêm. Đôi khi có thể thay khớp mới sau khi kiểm soát được nhiễm trùng. Khi mọi phương pháp khác đều thất bại, việc hàn cứng khớp gối là lựa chọn cuối cùng. Phương pháp này giúp chân ổn định và không đau, nhưng không thể gập được; nó chỉ được áp dụng khi mọi cách điều trị khác đều không hiệu quả.

Tóm lại: Nếu được điều trị kịp thời, hầu hết mọi người đều có thể giữ được khớp gối hoạt động bình thường. Nếu điều trị muộn hoặc không điều trị, sẽ có nguy cơ tổn thương lâu dài, cứng khớp và phải phẫu thuật thêm.

Khi nào nên đi khám bác sĩ

Đây không phải là tình trạng có thể chờ đợi vài ngày để xem diễn tiến ra sao. Một khớp gối nóng, sưng, đau dữ dội kèm sốt, đặc biệt nếu bạn không thể chịu được trọng lượng cơ thể lên khớp gối, thì cần được khám ngay trong ngày. Hãy đến phòng cấp cứu nếu có các dấu hiệu này, hoặc nếu bạn cảm thấy không khỏe trong người kèm theo các triệu chứng ở khớp gối. Tình trạng khẩn cấp tương tự cũng xảy ra nếu bạn đã từng thay khớp gối hoặc trải qua phẫu thuật khớp gối như tái tạo dây chằng chéo trước (ACL), và khớp gối đó bỗng trở nên nóng, sưng, đau kèm sốt. Nếu bạn mắc bệnh máu khó đông và việc điều trị chảy máu trong khớp gối không mang lại hiệu quả nhanh chóng, cần phải kiểm tra ngay xem có nhiễm trùng hay không. Hãy yêu cầu được bác sĩ chuyên khoa khám nếu khớp gối của bạn sưng và đau nhưng không có sốt hay chấn thương; hoặc nếu dấu hiệu nhiễm trùng khớp gối trước đây có vẻ tái phát.


Evidence & references

This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Overview

  • Knee arthrodesis is usually the last option available to the surgeon to obtain a painless, stable knee when the knee is not amenable to reconstruction [4].
  • Successful fusion is achieved in more than 90% of patients [4].
  • Septic arthritis is a less common indication for knee arthrodesis [4].
  • The most common indication for knee arthrodesis is the nonreconstructable TKA that has failed, usually because of infection and loss of the extensor mechanism [4].
  • Bilateral knee involvement is a contraindication for knee arthrodesis [4].
  • Ipsilateral hip arthrodesis is a contraindication for knee arthrodesis [4].
  • External fixation, plates, intramedullary rods, and combined modalities are used in knee arthrodesis [4].
  • If the limb-length discrepancy is less than 2 cm, the knee is placed in 5° to 7° of valgus and 15° of flexion [4].
  • If the limb-length discrepancy is 2 to 4 cm, the knee is placed in extension to enable ground clearance [4].
  • If the limb-length discrepancy is greater than 4 cm, bone grafting or a prosthetic spacer to limit gait abnormalities can be considered [4].
  • Painful nonunion is the most common complication of knee arthrodesis [4].
  • Infection is a complication of knee arthrodesis [4].
  • Deep vein thrombosis is a complication of knee arthrodesis [4].
  • Peroneal nerve palsy is a complication of knee arthrodesis [4].
  • Wound dehiscence is a complication of knee arthrodesis [4].
  • Long-term complications of knee arthrodesis include hip, spine, and ankle pain because of the altered gait pattern [4].

Anatomy & Pathophysiology

Bony Anatomy

  • The bones of the knee are the distal femur, the proximal tibia, and the patella [1].
  • The medial femoral condyle is larger and projects farther posteriorly and distally than the lateral condyle [6].
  • The lateral femoral condyle projects farther anteriorly and is wider in the medial-lateral direction than the medial femoral condyle [6].
  • The tibial articular surface slopes 7° to 10° in the sagittal plane [6].
  • The medial tibial plateau is larger than the lateral plateau and is concave in its frontal and sagittal planes [6].
  • The lateral tibial plateau is smaller and more circular than the medial plateau, concave in the frontal plane and convex in the sagittal plane [6].
  • The patella is the largest sesamoid bone in the body, averaging 2.5 cm in thickness [6].
  • The patellar articular surface contains a vertical, central ridge that separates the broader lateral facet from the medial facet, and a smaller, more medial facet called the odd facet [6].
  • The posterior slope of the medial tibial plateau is a mean of 10.7° and the lateral plateau is a mean of 7.2° [11].
  • The fibular head is located a mean of 1.5 cm distal to the joint line, with a range of 6 to 32 mm [11].

Ligaments

  • The anterior cruciate ligament (ACL) prevents anterior translation and rotation of the tibia on the femur [1].
  • The posterior cruciate ligament (PCL) prevents posterior subluxation of the tibia on the femur [1].
  • The medial collateral ligament stabilizes the knee to valgus stresses [1].
  • The lateral collateral ligament is the main stabilizer against varus stress [1].
  • The ACL is composed of 90% type I collagen and 10% type III collagen [6].
  • The mean length of the ACL is 33 mm and the mean midsubstance width is 11 mm [6].
  • The femoral attachment of the ACL is a semicircular area on the posteromedial aspect of the lateral femoral condyle [6].
  • The tibial attachment of the ACL is a broad, irregular, oval-shaped area slightly medial and anterior to the midline between the tibial spinous processes [6].
  • The PCL is the largest of the intra-articular ligaments, with an average length of 38 mm and a mean diameter at the midpoint of 13 mm [19].
  • The PCL has two distinct bundles: an anterolateral (AL) bundle comprising 85% of the cross-sectional area and a posteromedial (PM) bundle [19].
  • The PCL inserts onto a midline depression on the tibia, 10 to 15 mm below the level of the tibial plateaus [19].
  • The meniscofemoral ligaments are present in at least one form in 93% of knees [19].
  • The medial meniscus is firmly attached to the joint capsule along its entire peripheral edge [1].
  • The lateral meniscus is attached to the anterior and posterior capsule but has a region posterolaterally where it is not firmly attached [1].
  • The medial meniscus has less mobility than the lateral meniscus and is more susceptible to tearing when trapped between the femoral condyle and tibial plateau [1].
  • The lateral meniscus is larger than the medial meniscus and carries a greater share of the lateral compartment pressure [1].

Menisci

  • The menisci are C-shaped fibrocartilaginous disks that provide shock absorption, increase joint congruency, enhance stability, and aid in synovial fluid distribution [1].
  • The menisci provide a concave surface for the convex femoral condyles to articulate with [1].
  • Absence of menisci decreases the surface area of contact and increases pressure on the articular cartilage, which may lead to rapid deterioration of the joint surface [1].
  • Menisci consist of type I collagen fibers arranged obliquely, radially, and vertically [11].
  • Vascular supply to the menisci is derived from geniculate arteries, penetrating 20% to 30% of the peripheral medial meniscus and 10% to 25% of the peripheral lateral meniscus [11].

Vascular and Nerve Anatomy

  • The blood supply to the knee is formed from an anastomosis including the descending geniculate artery, superior and inferior geniculate arteries, middle geniculate artery, and anterior tibial recurrent arteries [6].
  • The middle geniculate artery supplies both the anterior and posterior cruciate ligaments [6].
  • The knee is innervated by branches of the femoral nerve (L2, L3, L4), obturator nerve (L2, L3, L4), and sciatic nerve (L4, L5, S1, S2) [6].
  • The posterior articular branch of the tibial nerve is the largest nerve providing innervation to the intra-articular knee [6].
  • The popliteus artery travels through the adductor hiatus where it is relatively immobile and distally through the fibrous arch deep to the soleus muscle [16].
  • The common peroneal nerve travels along the posterior edge of the biceps femoris and continues distally around the fibular neck [16].

Synovial Anatomy

  • The knee joint forms embryologically from three synovial compartments that normally fuse into a single synovial cavity [18].
  • Synovial plicae represent unresolved remnants of these partitions, including suprapatellar, infrapatellar, medial patellar, and lateral patellar plicae [18].
  • The medial patellar plica has an incidence ranging from 10% to more than 50% in normal knees [18].
  • A median septum may separate the posterior aspect of the knee into two compartments, with the PCL projecting anteriorly in the septum [21].

Kinematics

  • The knee is a hinge joint that incorporates both gliding and rolling motions [7].
  • The "screw-home" mechanism involves tibial external rotation of 5 degrees in the final 15 degrees of extension [7].
  • The greatest range of motion occurs in the sagittal plane, approximately 160° [23].
  • Knee rotation ranges from 45° in external rotation to 30° in internal rotation [23].
  • In the frontal plane, the range of motion in both abduction and adduction reaches a maximum of 10° [23].
  • During walking, knee range of motion in the sagittal, frontal, and transverse planes reaches approximately 70°, 15°, and 10°, respectively [23].
  • The normal instant center of the knee joint follows a semicircular path related to the tibiofemoral surface and ligaments [23].
  • Rupture of cruciate ligaments or disruption of the tibiofemoral surface causes a major change in the path of the instant center, leading to articular dysfunction [23].
  • The screw home mechanism occurs as the knee slightly hyperextends with slight tibial external rotation, tightening collateral and cruciate ligaments to lock the knee in extension [24].
  • Flexion is initiated by the popliteus muscle pulling the lateral femoral condyle backward while the medial femoral condyle slides forward, resulting in tibial internal rotation [24].

Clinical Presentation

History

  • A detailed history for knee pain diagnosis includes onset, quality, duration, tempo, and location of symptoms [33].
  • The history should include modifying factors, ability to bear weight, and history of trauma [33].
  • Key historical information includes current medications, history of injury or prior surgery, instability, and mechanical symptoms [34].
  • The history should document medical comorbidities, location of pain (unicompartmental or global), and response to previous treatments [34].
  • Symptom duration, temporal nature of pain, swelling, and distance able to ambulate are key historical elements [34].
  • The specific type of intra-articular knee injection used and the patient's response, including length of pain relief and magnitude of improvement, should be noted [34].
  • Patients who do not have temporary relief from an intra-articular injection should be evaluated for other pathology external to the knee joint [34].
  • Overweight patients should be asked about recent weight gain or loss and current weight-maintenance strategy [34].
  • Comorbidities such as renal or peptic ulcer disease may preclude oral anti-inflammatory medication use [34].
  • Social factors such as occupation or residence in a nursing home can affect the treatment strategy [34].

Physical Examination

  • A detailed physical examination of the knee includes inspection, palpation, gait assessment, range of motion testing, stability testing, neurovascular assessment, hip examination, and special tests [33].
  • Inspection of the knee can reveal skin abnormalities, evidence of trauma, malalignment, and swelling [33].
  • Inspection of the patient’s gait may reveal abnormalities that suggest either intra-articular or extra-articular causes [33].
  • Palpation of the knee with a focus on points of tenderness can alert the clinician to focal pathologies such as joint line tenderness, patellar tendon tenderness, or pes anserine bursa tenderness [33].
  • Palpation of the peripatellar tissue can reveal the presence of effusion and/or synovitis [33].
  • Overall knee alignment (varus, valgus, or neutral) should be assessed in both supine and standing positions, as bearing weight may change alignment dynamically [33].
  • Range of motion testing is divided into active range of motion (patient’s ability to move the knee) and passive range of motion (examiner’s ability to move the knee) [33].
  • Flexion contractures and hyperextension should be noted during range of motion testing [33].
  • Blocks to motion can be pain-related or mechanical, and differences between active and passive ranges of motion require differentiation between pain-related, mechanical, or neuromuscular causes [33].
  • Hip range of motion should be examined because it may reveal resultant knee pain indicating referred pain from intra-articular hip pathology [33].
  • Stability testing of the knee can reveal ligamentous competency or deficiency [33].
  • Basic varus and valgus stability testing should be performed at 0° and 30° of flexion [33].
  • Firm end points indicate ligament competence, while pronounced laxity can indicate ligament deficiency [33].
  • Testing at 30° of flexion isolates the MCL and LCL best, as testing in full extension also engages some secondary stabilizers [33].
  • ACL competence can be tested using the Lachman test, which involves flexing the knee to 30°, holding the femur firmly, and translating the tibia anteriorly on the femur [33].
  • A positive Lachman test is indicated by no firm end point and significant translation [33].
  • PCL competence can be tested using the posterior drawer test, which involves flexing the knee to 90° with the patient supine, stabilizing the distal tibia, and translating the tibia posteriorly on the femur [33].
  • A positive posterior drawer test is indicated by no firm end point and significant translation [33].
  • Patellar maltracking can be assessed using the J-sign, which involves bringing the knee from full extension into flexion to observe a visible patellar shift from lateral to medial in a J-shaped path [33].
  • Lateral meniscus tears can be assessed using the McMurray test, which involves flexing the knee, internally rotating the tibia, extending the knee, and applying pressure to the lateral joint line [33].
  • Medial meniscus tears can be assessed using the McMurray test, which involves flexing the knee, externally rotating the tibia, extending the knee, and applying pressure to the medial joint line [33].
  • A positive McMurray test is indicated by pain or click with the maneuver [33].
  • PLC deficiency can be assessed using the dial test, which involves placing the patient prone with the knee flexed to 30° and externally rotating both tibiae [33].
  • PLC plus PCL deficiency can be assessed using the dial test, which involves placing the patient prone with the knee flexed to 90° and externally rotating both tibiae [33].
  • A positive dial test is indicated by greater than 10° difference from the contralateral side [33].
  • The patient’s gait, lower body alignment, range of motion, and ligamentous stability should be assessed and documented [34].
  • Catching or locking, instability in the coronal and/or sagittal plane, or an effusion can signal the presence of a mechanical pathology warranting surgical treatment [34].
  • The lumbar spine and hips should be examined because pathology in one of these locations can present as referred pain to the knee [34].
  • The lower extremities should be examined for evidence of muscular atrophy or weakness, with particular attention to hip abductor and quadriceps strength [34].
  • Distal sensation and vascular perfusion (peripheral pulses) should be assessed in all patients, and any abnormalities should be documented [34].
  • Key physical examination findings include previous incisions, effusion, range of motion, joint line tenderness, ipsilateral hip examination, lower extremity strength (quadriceps, gluteus), peripheral pulses and sensation, alignment (varus/valgus/neutral, and if deformity, rigid or flexible), and gait [34].
  • Hip osteoarthritis can refer to the knee via the obturator nerve [34].

Imaging

  • Baseline weight-bearing radiographs of the knee should be obtained in all patients with symptomatic osteoarthritis of the knee [34].
  • A standing PA view obtained with the patient’s knee in 45° of flexion is often preferred over the standard standing AP view [34].
  • The 45° flexion view allows better evaluation of the posterior femoral condyles and earlier detection of subtle joint-space loss than the AP view [34].
  • Additional radiographs should include a lateral view of the affected side and a Merchant or sunrise view of the patellofemoral joint [34].

Investigations

Plain Radiography

  • Plain radiographs are appropriate initial imaging studies for most knee conditions because they allow the assessment of traumatic injury, arthritis, patellofemoral alignment, osteochondral injury, bone neoplasm, and surgical implants [3].
  • Radiographic studies help confirm the clinical diagnosis of a joint disorder determined using the patient’s history and physical examination [3].
  • Imaging studies should include at least two perpendicular views: AP and lateral [3].
  • Weight-bearing AP (extension) views are used to assess cartilage loss from the distal femur and tibial plateau [3].
  • Weight-bearing PA (Rosenberg; flexion) views are used to assess cartilage loss from the posterior femur and tibial plateau [3].
  • Patellofemoral views are used to assess patellofemoral alignment (tilt/subluxation), patellar and trochlear morphology, osteochondral injury, and patellofemoral arthritis [3].
  • A notch view is used to assess posterior femoral cartilage, notch width, and osteophytes [3].
  • Radiography may identify subchondral sclerosis, joint space narrowing, subchondral cysts (variable), osteophytes (variable), and joint subluxation in osteoarthritis [3].
  • Radiography may identify joint space loss and peripheral bone erosion in inflammatory arthropathy [3].
  • Radiography may identify subchondral radiolucency in osteochondral defects, which is most common in the medial femoral condyle [3].
  • Radiography may identify linear radiolucency or radiodensity in stress fractures, which are most common in the proximal medial tibia [3].
  • Radiography may identify a mixed sclerotic pattern with a subchondral, epiphyseal, or metaphyseal location in osteonecrosis [3].
  • Radiography may identify malalignment, osteophytes, cysts, and joint space loss in patellofemoral disease [3].
  • Non–weight-bearing radiographs may identify acute injury without the risk of fracture displacement in trauma [3].
  • Lateral capsular avulsion (meniscotibial ligament) is pathognomonic but not essential for ACL injury, and hemarthrosis is frequently present [3].
  • Avulsion of the medial femoral epicondyle (Pellegrini-Stieda lesion) may appear within a few weeks of proximal MCL avulsion injury [3].
  • Supine AP knee radiographs are most frequently used but do not adequately estimate the joint space width needed to estimate the degree of osteoarthritis progression [29].
  • Plain frontal radiographs of the knee may not accurately display the actual joint space due to different cartilage wear patterns, meniscal integrity, or variances in tibial slopes [29].
  • A 45° standing flexion view was introduced by Rosenberg et al. to better evaluate joint space [29].
  • A fixed flexion view (FFV) technique has been introduced with improved reproducibility and good evaluation of the joint space [29].
  • The Lyon Schuss view (LSV) uses the same posture as the FFV but requires fluoroscopic adjustment of the irradiation angle relative to the medial tibial plateau, which is more accurate for measuring actual joint space width [29].
  • The radiation exposure dose for the Lyon Schuss view is higher and positioning is more complex and time-consuming than for the FFV [29].
  • Goniometer readings of long limb alignment or measured on an FFV correlated well with the angle measured on long limb radiographs, providing an alternative imaging source if long limb radiographs are not available [29].
  • Radiographs are still the standard for initial evaluation of knee pain [25].
  • Images for initial evaluation should include weight-bearing AP and lateral views, a view of the weight-bearing knee flexed at 45-degree angle imaged posterior to anterior, a sunrise view (Merchant view), extension and flexion lateral views, and a standing full-length AP radiograph [25].
  • A standing full-length AP radiograph from hip joint to ankle joint is used to evaluate limb alignment and knee deformity and to identify femoral and/or tibial bone deformity [25].
  • The Kellgren-Lawrence (KL) rating grades extent of OA based on review of AP knee radiograph [25].
  • Primary features used for KL rating include osteophytes (periarticular and tibial spine), joint space narrowing, subchondral sclerosis with or without subchondral cysts, and altered shape of periarticular bones [25].
  • KL Grade 0 indicates normal knee features with no OA [25].
  • KL Grade 1 indicates OA possibly present [25].
  • KL Grade 2 indicates OA present with minimal severity [25].
  • KL Grade 3 indicates OA present with moderate severity [25].
  • KL Grade 4 indicates OA present with severe severity [25].
  • Knee arthroplasty is recommended when Grade 4 findings are present [25].

Computed Tomography

  • Computed tomography is a three-dimensional study performed with ionizing radiation that provides enhanced bone detail [3].
  • Imaging in the axial, sagittal, and coronal planes may help visualize fracture lines and displacement, osteolytic lesions around joint arthroplasty, and cortical disruption in cases of infection or neoplasia [3].
  • Three-dimensional reconstructions may help with preoperative planning for complex intra-articular fractures, multiplanar osteotomy for limb malalignment, and reconstitution of bone loss in joint arthroplasty [3].
  • Axial plane imaging of the hip and knee can help assess the rotational alignment of components of a total knee arthroplasty in cases of patellar maltracking [3].
  • Three-dimensional CT with remodeling is used for preoperative planning for reconstruction associated with dysplasia, post-trauma planning, and complex total knee arthroplasty (TKA) planning [25].

Magnetic Resonance Imaging

  • Increasing strength of the magnetic field (measured in Tesla units) increases the resolution of images [3].
  • An injected contrast agent (intravenous or intra-articular) may help delineate specific tissues of interest [3].
  • MRI may suggest cruciate ligament injury through the presence of edema, intra-articular fluid, disruption of ligament fibers, and an atypical ligament contour [3].
  • MRI can identify patterns of meniscal injury by location (anterior, midbody, posterior, peripheral, articular), pattern (horizontal, longitudinal, radial, complex), and displacement [3].
  • MRI may identify the degree of articular cartilage injury (chondrosis, full-thickness cartilage loss), the presence of associated bone marrow edema, and the location (medial condyle, lateral condyle, trochlea, patella; anterior, posterior) [3].
  • MRI may identify edema, avulsion, or discontinuity for the MCL/lateral collateral ligament (LCL) or associated posteromedial and posterolateral ligamentous complexes [3].
  • MRI may be used to assess the continuity of the quadriceps or patellar tendon [3].
  • MRI may be used to assess the margin of resection for a neoplasm, identify vascular malformation, or define the location of nerves or vessels relative to popliteal cysts [3].
  • MRI is the most useful study for differentiating osteonecrosis from other conditions [31].
  • Bone edema on MRI is a common feature of OA, osteonecrosis, cartilage injury, and transient regional osteoporosis [31].
  • Serpentine lesions within a well-demarcated border is a specific finding on MRI for osteonecrosis [31].
  • MRI is grossly overused in the arthritic patient population [25].
  • If the joint space is significantly narrowed on radiograph, then MRI is not indicated [25].
  • MRI is used when osteonecrosis is suspected [25].
  • Radiographic evaluations are essential when diagnosing an OCD lesion of the knee and elbow; however, important aspects of the OCD lesions may be better seen with MRI [28].
  • A systematic review quantified the accuracy of MRI for detection of meniscal injury and ACL tear [22].
  • Compositional MRI techniques (T1ρ, T2*, dGEMRIC, gagCEST) are used for early recognition of cartilage degeneration [22].

Nuclear Medicine

  • Nuclear medicine involves labeled radionuclide injection followed by delayed imaging of gamma radiation [3].
  • Areas of increased radionuclide concentration appear bright or “hot” [3].
  • Nuclear medicine provides a nonspecific study that does not define the etiology of an abnormality but rather the presence of an abnormality that may correlate with a clinical concern [3].
  • Increased radionuclide activity in bone may be a normal postoperative finding for up to 6 to 12 months after a fracture repair or arthroplasty [3].
  • Technetium-99 (Tc-99) is a radionuclide that may help identify infection, neoplasia, occult fracture, bone healing, active phases of heterotopic ossification, implant loosening, or failure of osseointegration [3].
  • Gallium-67 (Ga-67) is a radionuclide that may help differentiate between aseptic and septic prosthetic loosening; 24 to 72 hours are needed for a complete study [3].

Physical Examination

  • The physical examination begins with observation of the patient’s gait [1].
  • The uninjured knee is examined as a basis of comparison with the injured knee [1].
  • Any swelling or effusion should be noted during physical examination [1].
  • A small effusion will cause obliteration of the recesses on the medial and lateral aspects of the patellar tendon [1].
  • With a larger effusion, diffuse swelling is present in the region of the suprapatellar pouch [1].
  • A fluid wave can be palpated on the sides of the patella [1].
  • Active and then passive range of motion is tested carefully [1].
  • The knee is palpated to define areas of localized tenderness [1].
  • The joint lines are located at the level of the inferior pole of the patella when the knee is flexed to 90 degrees [1].
  • Patient assessment of knee pain includes a physical examination and diagnostic radiographic modalities [25].
  • Pain with weight bearing is aggravated by stairs, inclines, and transition from sit to stand [25].
  • Bowing deformity and instability are seen later in the clinical presentation of knee pain [25].
  • Knee thrust is seen later in the clinical presentation and indicates ligament stretch-out on the convex side of the thrust [25].
  • Varus thrust occurs when the knee pushes outward during stance phase of gait, overloading the medial compartment and accelerating cartilage degeneration in the medial compartment [25].
  • Valgus thrust occurs when the knee pushes inward during stance phase of gait, overloading the lateral compartment and accelerating cartilage degeneration in the lateral compartment [25].
  • Assessment of the joint must combine physical examination along with radiographic (including full-length alignment views) and MRI findings [32].

Treatment

Arthrodesis

  • The most common indication for knee arthrodesis is the nonreconstructable total knee arthroplasty (TKA) that has failed, usually because of infection and loss of the extensor mechanism [4].
  • If the limb-length discrepancy (LLD) is less than 2 cm, the knee is placed in 5° to 7° of valgus and 15° of flexion for arthrodesis [4].
  • If the LLD is 2 to 4 cm, the knee is placed in extension to enable ground clearance for arthrodesis [4].
  • If the LLD is greater than 4 cm, bone grafting or a prosthetic spacer to limit gait abnormalities can be considered for arthrodesis [4].
  • Complications of knee arthrodesis include infection, deep vein thrombosis, peroneal nerve palsy, and wound dehiscence [4].

General Management Principles

  • Infection of the knee can be a devastating process, and rapid surgical and antibiotic appropriate care should be facilitated by orthopaedic surgeons [36].
  • Rapid and appropriate surgical and antibiotic care should be facilitated by orthopaedic surgeons to prevent further cartilage destruction in cases of knee infection [36].
  • Recent or current knee sepsis is an absolute contraindication to total knee arthroplasty (TKA) [5].
  • A remote source of ongoing infection is an absolute contraindication to total knee arthroplasty (TKA) [5].

References

[1] A Lange Medical Book Current Diagnosis Treatment In Orthopedics Fifth Edition. 3Sports Medicine > Image KNEE INJURIES.

[3] Aaos Comprehensive Orthopaedic Review 3. Radiographic Evaluation and Surgical Anatomy of the Knee > I. Radiographic Evaluation.

[4] Aaos Comprehensive Orthopaedic Review 3. Nonarthroplasty Surgical Treatment of the Knee > IV. Knee Arthrodesis.

[5] Campbell S Operative Orthopaedics 4 Volume Set. TOTAL KNEE ARTHROPLASTY.

[6] Aaos Comprehensive Orthopaedic Review 3. Anatomy and Biomechanics of the Knee > I. Anatomy.

[7] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 1 KNEE > ANATOMY (FIG. 4.1).

[11] Aaos Comprehensive Orthopaedic Review 3. Radiographic Evaluation and Surgical Anatomy of the Knee > II. Surgical Anatomy of the Knee.

[16] Aaos Comprehensive Orthopaedic Review 3. Knee Dislocations and Patellar Fractures* > I. Knee Dislocations.

[18] Campbell S Operative Orthopaedics 4 Volume Set. TRANSTIBIAL PULL-OUT REPAIR OF RADIAL OR MENISCAL ROOT TEAR > SYNOVIAL PLICAE OF THE KNEE.

[19] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Posterior Knee Anatomy.

[21] Campbell S Operative Orthopaedics 4 Volume Set. SINGLE-INCISION POSTEROLATERAL APPROACH TO THE LATERAL AND POSTERIOR MALLEOLI > POSTEROLATERAL AND POSTEROMEDIAL APPROACHES TO THE KNEE.

[22] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Arthroscopy and Preservation, Knee Reconstruction > Annotated References.

[23] Aaos Comprehensive Orthopaedic Review 3. Biomechanics and Wear in Joint Arthroplasty > III. The Knee Joint.

[24] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Anatomy > Knee Kinematics.

[25] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 11 KNEE ARTHRITIS ASSESSMENT.

[28] Orthopaedic Knowledge Update. Osteochondritis Dissecans of the Knee and Elbow* > Summary.

[29] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Anatomy > Imaging (Radiograph, MRI, CT Scan, Dynamic Versus Static) > Radiograph.

[31] Aaos Comprehensive Orthopaedic Review 3. General Evaluation of the Knee Patient > III. Osteonecrosis.

[32] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Arthroscopy and Preservation, Knee Reconstruction > Summary.

[33] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Anatomy > History and Physical Examination.

[34] Orthopaedic Knowledge Update Sports Medicine 6. Nonarthroplasty Management of Osteoarthritis of the Knee > Patient Evaluation.

[36] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Degenerative Conditions of the Knee > Summary.

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For the avoidance of doubt, this Section 4 supplements and does not replace Your obligations under this Public License where the Licensed Rights include other Copyright and Similar Rights.

Section 5 -- Disclaimer of Warranties and Limitation of Liability.

a. UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.

b. TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT, INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES, COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.

c. The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.

Section 6 -- Term and Termination.

a. This Public License applies for the term of the Copyright and Similar Rights licensed here. However, if You fail to comply with this Public License, then Your rights under this Public License terminate automatically.

b. Where Your right to use the Licensed Material has terminated under Section 6(a), it reinstates:

1. automatically as of the date the violation is cured, provided it is cured within 30 days of Your discovery of the violation; or

2. upon express reinstatement by the Licensor.

For the avoidance of doubt, this Section 6(b) does not affect any right the Licensor may have to seek remedies for Your violations of this Public License.

c. For the avoidance of doubt, the Licensor may also offer the Licensed Material under separate terms or conditions or stop distributing the Licensed Material at any time; however, doing so will not terminate this Public License.

d. Sections 1, 5, 6, 7, and 8 survive termination of this Public License.

Section 7 -- Other Terms and Conditions.

a. The Licensor shall not be bound by any additional or different terms or conditions communicated by You unless expressly agreed.

b. Any arrangements, understandings, or agreements regarding the Licensed Material not stated herein are separate from and independent of the terms and conditions of this Public License.

Section 8 -- Interpretation.

a. For the avoidance of doubt, this Public License does not, and shall not be interpreted to, reduce, limit, restrict, or impose conditions on any use of the Licensed Material that could lawfully be made without permission under this Public License.

b. To the extent possible, if any provision of this Public License is deemed unenforceable, it shall be automatically reformed to the minimum extent necessary to make it enforceable. If the provision cannot be reformed, it shall be severed from this Public License without affecting the enforceability of the remaining terms and conditions.

c. No term or condition of this Public License will be waived and no failure to comply consented to unless expressly agreed to by the Licensor.

d. Nothing in this Public License constitutes or may be interpreted as a limitation upon, or waiver of, any privileges and immunities that apply to the Licensor or You, including from the legal processes of any jurisdiction or authority.


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