Early knee osteoarthritis poses a therapeutic dilemma to the musculoskeletal clinician. Despite the recent interest in arthroscopic and injectable regenerative therapies intended to repair or restore a focal target such as cartilage, meniscus, or subchondral bone, none have been shown to slow disease progression.
A likely cause of these disappointing treatment outcomes is the failure to address chronic and excessive loading of the knee joint. A growing body of evidence suggests that first-line therapies for early knee osteoarthritis should emphasize unloading the knee joint since any potential therapeutic benefit of regenerative therapies will likely be attenuated by excessive mechanical demand at the knee joint. Minimally invasive medical devices such as patient-specific interpositional implants and extracapsular joint unloading implants are currently in development to address this clinical need.
Excerpt from Elizabeth A. Arendt, Larry E. Miller, Jon E. Block. Orthop Rev (Pavia). 2014 Jan 20
|Early knee osteoarthritis management|
In the period between initial diagnosis and definitive surgical management, patients may be prescribed numerous nonsurgical management strategies, either alone or concomitantly.
Although pharmacological therapy improves knee OA symptoms in many cases, no nonsurgical treatment has been shown to slow disease progression. Paradoxically, conservative therapies may actually encourage OA progression in responders since patients may become more physically active, leading to higher peak adduction moments across the knee joint.
Over 80% of orthopedic surgeons agreed that better treatment alternatives are needed in younger OA patients in which arthroplasty is not indicated, and over 2 in 3 perceived a treatment gap for early knee OA. Clearly, the current approach to knee OA treatment, including early knee OA, is often ineffective. Therapies should be targeted to specific disease phases that not only alleviate symptoms, but also address the underlying etiology.
Arthroscopic and injectable regenerative therapies intended to repair or restore a focal target such as cartilage, meniscus, or subchondral bone have demonstrated limited clinical usefulness to date for several reasons. First, early knee OA is not a focal disease but, instead, affects the entire joint including articular cartilage, the menisci, periarticular muscles, ligaments, subchondral bone, and synovial membrane. Second, targeted tissue repair or regeneration likely will not overcome the deleterious effects of chronic biomechanical abnormalities of the knee joint, which is the strongest modifiable risk factor for knee OA development and progression.
Following this logic, a first-line therapy for the patient with early knee OA should focus on chronically unloading the knee joint before any attempts are made at tissue regeneration or repair. Experimental regenerative approaches that involve use of juvenile cartilage, scaffolds and various polymeric matrices are unable to generate normal hyaline cartilage that can adequately integrate with host tissue and sustain physiological biomechanical loads.
Additionally, the disorganized structural organization of the regenerated tissue remains highly susceptible to injury and does not prevent enlargement of the defect in the host cartilage. Consequently, any potential therapeutic benefit of regenerative therapies for early knee OA will likely be attenuated by excessive mechanical demand that exceeds the ability of the joint to repair itself.
Although little direct evidence for the influence of joint loading on the efficacy of regenerative therapies is available, this hypothesis is supported by others. Mazzuca et al, conducted a post hoc analysis of a randomized controlled trial investigating the influence of doxycycline or placebo on medial joint narrowing in obese women with knee OA. While doxycycline slowed the rate of medial joint space narrowing by 33% at 30 months, the treatment effect was negated in patients with varus alignment.
Unloading the knee of excessive forces may slow or potentially reverse OA progression, negating the need for regenerative therapy. Nonsurgical treatments such as wedged sole insoles, knee braces, weight loss, and muscular strength training reduce knee joint loading and may alleviate OA symptoms. However, these treatments rarely achieve long-term symptomatic control.
Early knee osteoarthritis management should first address mechanical joint overload, Elizabeth A. Arendt, Larry E. Miller, Jon E. Block. Orthop Rev (Pavia). 2014 Jan 20; 6(1): 5188. Published online 2014 Mar 18. doi: 10.4081/or.2014.5188. Full text
Conservative management of symptomatic knee osteoarthritis: a flawed strategy? Crawford DC, Miller LE, Block JE. Orthop Rev (Pavia). 2013 Feb 22;5(1):e2. doi: 10.4081/or.2013.e2. Print 2013 Feb 22. Full text