Osteoarthritis of the knee
Citation, DOI and article data
Osteoarthritis (OA) of the knee is very common and is a major cause of morbidity, especially in the older population.
The term early osteoarthritis of the knee has been proposed and has been defined as meeting three main criteria 9:
- knee pain
- ≤Kellgren-Lawrence grade 2 on radiographs
- arthroscopic cartilage lesion and/or OA-related MRI findings such as subchondral bone marrow lesions and/or cartilage and meniscal degeneration
Knee OA is very common and is the most common joint disease in the elderly. In the community, it is estimated to affect ~12.5% of patients >45 years 8.
The medial femorotibial joint compartment is more commonly affected and often more severe compared to the lateral 2.
The hallmarks of knee osteoarthritis are the same for most other joints 6:
- joint space narrowing
- usually asymmetric, typically of the medial tibiofemoral compartment, and/or patellofemoral compartment 3
- <3 mm on weight-bearing knee radiographs is considered a finding of absolute joint space narrowing with a normal joint space >5 mm 7
- weight-bearing radiographs will demonstrate more joint space narrowing than non-weight-bearing radiographs, hence affecting the radiographic severity 7,8
- subchondral sclerosis
- marginal osteophytes
- subchondral cysts (geodes)
- altered shape of the femoral condyles and tibial plateau
Plain radiographs are the workhorse of imaging including follow-up, although there is a poor correlation between radiographic findings and clinical symptoms 1,2.
The initial study of any patient with suspicion of knee osteoarthritis should include a Rosenberg view, a PA radiograph with weight-bearing and 45 degrees of flexion, which is more sensitive to detect joint space narrowing 5.
The following features are seen additionally on MRI 1,10:
- effusion and synovial thickening / synovitis
- subchondral bone marrow edema and/or cysts
- cartilaginous defects (partial or full-thickness)
- iliotibial band syndrome
Treatment and prognosis
Non-operative management involves simple analgesia and weight loss. However, patients will often eventually require joint replacement. Total knee joint replacement is effective. Unicompartmental joint replacement may be considered in some institutions for cases where the disease is predominantly isolated to a single joint compartment.
Other causes of degenerative joint disease, for example:
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- 2. Hayes CW, Jamadar DA, Welch GW et-al. Osteoarthritis of the knee: comparison of MR imaging findings with radiographic severity measurements and pain in middle-aged women. Radiology. 2005;237 (3): 998-1007. doi:10.1148/radiol.2373041989 - Pubmed citation
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- 4. Heidari B. Knee osteoarthritis diagnosis, treatment and associated factors of progression: part II. Caspian J Intern Med. 2014;2 (3): 249-55. Free text at pubmed - Pubmed citation
- 5. Fontboté R C, Nemtala U F, Contreras O O, Guerrero R. [Rosenberg projection for the radiological diagnosis of knee osteoarthritis]. (2008) Revista medica de Chile. 136 (7): 880-4. doi:/S0034-98872008000700009 - Pubmed
- 6. Mark D. Kohn, Adam A. Sassoon, Navin D. Fernando. Classifications in Brief: Kellgren-Lawrence Classification of Osteoarthritis. (2016) Clinical Orthopaedics and Related Research®. 474 (8): 1886. doi:10.1007/s11999-016-4732-4 - Pubmed
- 7. Leach RE, Gregg T, Siber FJ. Weight-bearing radiography in osteoarthritis of the knee. (1970) Radiology. 97 (2): 265-8. doi:10.1148/97.2.265 - Pubmed
- 8. Alvin Chen, Joshua Balogun-Lynch, Kavita Aggarwal, Elizabeth Dick, Chinmay M Gupte. Should all elective knee radiographs requested by general practitioners be performed weight-bearing?. (2014) SpringerPlus. 3 (1): 707. doi:10.1186/2193-1801-3-707 - Pubmed
- 9. Nagai K, Nagai NT, Nagai FFH. The diagnosis of early osteoarthritis of the knee using magnetic resonance imaging. (2018) Annals of Joint.
- 10. Hunter DJ, Guermazi A, Lo GH, Grainger AJ, Conaghan PG, Boudreau RM, Roemer FW. Evolution of semi-quantitative whole joint assessment of knee OA: MOAKS (MRI Osteoarthritis Knee Score). (2011) Osteoarthritis and cartilage. 19 (8): 990-1002. doi:10.1016/j.joca.2011.05.004 - Pubmed