Loading conditions of the knee: what does it mean?

Abstract

Ó Springer-Verlag Berlin Heidelberg 2013 Bracing, for unloading the knee on healthy subjects, was studied in the leading article of the current issue by Orishimo et al. [12]. Loading or unloading the knee is a very interesting and important aspect when postsurgical treatment of cartilage or meniscal lesions is discussed.Research about knee loading has been of interest for more than 30 years using finite element models [2], force plates [5] and in vivo technology [15]. Some very interesting in vivo data have shown that walking causes femorotibial peak forces of 261 % body weight and descending stairs up to 346 % of body weight [7]. Knee loading can increase up to 550 % body weight during sudden balance loss, showing the importance of the interaction of the muscles. It is well known that the medial compartment takes significantly more load than the lateral one, which is on average 60-70 % of the load during level walking. Loading can rise significantly in osteoarthritic knees [6,8].A minor change in leg alignment shifts the load to the medial or lateral compartment. This has been known for many years and has been the basis for internal or external correction of the leg alignment [1,13].Gait analyses have shown that the adduction moment depends more on leg alignment rather than the degree of OA [4]. The adduction moment serves as the surrogate for medial compartment load.Despite the strong correlation between the mechanical axis and the adduction moment, other factors such as increased rearfoot eversion, rearfoot internal rotation and forefoot inversion cause reduction in loading of the medial compartment [9]. Thus, it seems to make sense to perform a ''brace-test'', for instance, before high tibial osteotomy is considered in osteoarthritic knees. By using a brace in 4°a nd 8°valgus in osteoarthritic knees, the reduction in medial tibial loading was 24 and 30 %, respectively [8]. However, this data seem to depend on the type of brace.As previously mentioned, Orishimo et al. [12] performed their study on healthy subjects and not on patients suffering from osteoarthritis. Increased valgus stress decreased the adduction moment by 32 %. These data are comparable to findings in osteoarthritic patients. However, what would the clinical relevance be of lowering the adduction moment by 20 or 30 %? How much unloading of a compartment would be required to improve clinical symptoms, allow cartilage regeneration and or meniscus healing?The current guidelines of postsurgical knee loading after cartilage repair, meniscus surgery or osteotomy are mainly based on clinical experience. However, there is published data which, for example show that by decreasing the adduction to \2.5 % body weight 9 height in patients after high tibial osteotomy showed better clinical outcome compared to patients without bracing [14].How much correction do we need in order to not only relieve pain but also prevent progression of femorotibial OA? Many authors refer in clinical and basic science studies to the Fujisawa-point, a point where the mecha...

Two-Year Results of the PHANTOM High Flex Trial: A Single-Arm Study on the Atlas Unicompartmental Knee System Load Absorber in Patients With Medial Compartment Osteoarthritis of the Knee

“…Although an HTO can unload the joint, the procedure involves invasive bone alterations, a potentially prolonged recovery, and may actually accelerate OA in the lateral compartment as a result of the longer term load shifting to this compartment. 3,4,13 The procedure is also contraindicated in those with malalignment based purely on degenerative changes. 8,15 Joint distraction has also been investigated, but the distraction fixator can cause discomfort, pin site infection, and osteomyelitis 2,15 ; in comparison, no infections occurred during this trial.…”

“…2 Many of these patients with knee osteoarthritis (OA) have unicompartmental disease of the medial compartment. 3-6…”

Feasibility of the Atlas Unicompartmental Knee System Load Absorber in Improving Pain Relief and Function in Patients Needing Unloading of the Medial Compartment of the Knee: 1-Year Follow-Up of a Prospective, Multicenter, Single-Arm Pilot Study (PHANTOM High Flex Trial)

“…[1][2][3][4][5][6][7] Many of these younger patients have unicompartmental knee OA, which most frequently occurs in the medial compartment, as it takes on significantly more load during weight bearing than the lateral compartment. [8][9][10][11] Treatment for medial compartment knee OA typically begins with nonsurgical therapies, such as weight loss, orthotics, analgesics, anti-inflammatory drugs, and joint injections, although they may eventually fail as they do not correct the underlying pathology. 2,4 Patients may then progress to surgical intervention, namely, arthroplasty or high tibial osteotomy (HTO).…”

“…1–7 Many of these younger patients have unicompartmental knee OA, which most frequently occurs in the medial compartment, as it takes on significantly more load during weight bearing than the lateral compartment. 8–11…”

“…20,23 Meanwhile, HTO, despite some clinical success, has been less popular with patients and surgeons in certain cultures because it involves invasive bone alterations, a potentially prolonged recovery, and may actually accelerate OA in the lateral compartment as a result of the load shifting to this compartment. 3,8,9 With higher revision and dissatisfaction rates after arthroplasty and an aversion to HTO, there is a clear clinical need to be addressed for the younger patient with knee OA.…”