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Implantable Shock Absorber (MISHA)
The MISHA Knee System
The MISHA® Knee System is an implantable shock absorber designed for certain patients with pain coming primarily from the medial (inner) compartment of the knee. Unlike traditional knee replacement, the MISHA implant is placed outside the joint capsule and is intended to reduce load across the inner side of the knee while preserving the native joint surfaces.
What Is the MISHA Knee System?
The MISHA Knee System is an extra-capsular implant fixed to the femur and tibia on the inner side of the knee. It contains a shock-absorbing component that helps share load with the medial compartment during walking and daily activity. Because it is placed outside the joint and does not require joint resurfacing or removal of the knee joint itself, it offers a joint-preserving option for appropriately selected patients.
In simple terms, the device functions like an internal shock absorber for the inner side of the knee. Its goal is to reduce painful overload in the part of the knee most affected by arthritis while allowing the knee to keep its natural anatomy.
Who May Be a Candidate?
The MISHA Knee System may be an option for patients who:
- have pain primarily on the inner (medial) side of the knee
- have medial compartment knee osteoarthritis
- continue to have pain that interferes with activities of daily living
- have not found enough relief with prior nonsurgical and/or surgical treatment
- are unwilling to undergo total knee replacement or may not be ideal candidates for total knee replacement because of age or because they do not yet have advanced osteoarthritis throughout the knee
The best candidates are patients whose symptoms, examination, and imaging all support that the medial compartment is the primary source of pain.
Who May Not Be a Candidate?
The MISHA Knee System is not right for everyone. It may not be appropriate in patients with certain conditions, including:
- poor bone quality such as osteopenia or osteoporosis
- ligamentous instability
- active or recent knee infection
- inflammatory joint disease
- suspected allergy or hypersensitivity to certain metals
- large medial osteophytes or a significantly extruded meniscus that could interfere with placement or function of the implant
A full evaluation, including X-rays and often MRI review, is important to determine whether this implant is appropriate.
How Does It Work?
The MISHA implant is designed to reduce load through the inner side of the knee during walking. Biomechanical research has shown that the implant can reduce peak medial compartment force by about 32% during gait. By unloading the diseased compartment, the device aims to improve pain and function while preserving the natural knee joint.
How Is It Different from Knee Replacement?
Traditional knee replacement resurfaces damaged joint surfaces with metal and polyethylene components. The MISHA Knee System works differently. It does not replace the joint surfaces. Instead, it is implanted alongside the knee to help absorb shock and reduce load on the painful medial compartment.
This makes it an appealing option for some patients who feel they are not ready for knee replacement or who want to consider a joint-preserving alternative first.
Potential Benefits
- joint-preserving treatment option
- designed to reduce painful load on the medial compartment
- does not require resurfacing the knee joint
- future treatment options, including knee replacement, may still remain available if needed later
- meaningful improvements in pain and function have been reported in published studies
What Have Studies Shown?
Published studies on implantable shock absorber technology have shown encouraging results in appropriately selected patients with medial compartment knee osteoarthritis.
- Biomechanical studies have shown approximately 32% reduction in peak medial compartment force during walking.
- A five-year study reported an 85% survival from arthroplasty, meaning most patients had not gone on to knee replacement by five years.
- A more recent review reported mean WOMAC pain improvement of 71% and function improvement of 69%, with reported three-year survivorship around 97.3% in later subgroup data.
These results are promising, but patient selection remains very important. Not every knee with arthritis is a good fit for this technology.
The Procedure
The MISHA implant is placed through a surgical procedure on the inner side of the knee. The device is positioned superficial to the medial collateral ligament and fixed to the femur and tibia. Because it is extra-capsular, it is designed to be implanted without resecting bone, muscle, or ligaments and without disrupting the joint capsule.
Recovery
Recovery varies depending on the patient and whether any other procedures are performed at the same time. In general, recovery focuses on incision healing, restoration of motion, gradual strengthening, and progressive return to daily activities. Your surgeon will guide weight-bearing status, activity progression, and physical therapy based on your specific case.
Risks and Considerations
As with any implant surgery, there are risks. Potential adverse effects listed in the device instructions for use include:
- infection
- soft tissue discomfort around the implant
- implant failure or failure to improve symptoms
- nerve or ligament injury
- adverse tissue reaction
- need for additional surgery, including possible removal or reconstruction
MRI Information
The current instructions for use state that a person with the MISHA Knee System may be scanned under specified MRI conditions, including 1.5T and 3T cylindrical scanners. Patients should always inform imaging centers that they have a MISHA implant before undergoing MRI.
Is MISHA Right for You?
If you have persistent medial knee pain from arthritis and want to learn whether a joint-preserving alternative may be appropriate, an evaluation with review of your symptoms, imaging, alignment, ligament stability, and prior treatment can help determine whether the MISHA Knee System is a reasonable option for you.
References
- U.S. Food and Drug Administration / MISHA Knee System Instructions for Use. Current labeling describes MISHA as an extra-capsular implant intended to reduce loads on the medial knee and lists its indications, contraindications, adverse effects, and MRI conditions.
- Morgan OJ, Hillstrom HJ, Ranawat A, Fragomen AT, Rozbruch SR, Hillstrom R. Effects of a Medial Knee Unloading Implant on Tibiofemoral Joint Mechanics During Walking. Journal of Orthopaedic Research. 2019;37(10):2149-2156.
- Gomoll AH, Diduch DR, Flanigan DC, Ranawat AS, Slynarski K, Walawski J, Crawford DC. An implantable shock absorber yields an 85% survival-from-arthroplasty rate through 5 years in working-age patients with medial compartment knee osteoarthritis. Knee Surgery, Sports Traumatology, Arthroscopy. 2023;31(8):3307-3315.
- Raji Y, and colleagues. Medial Implantable Shock Absorber (MISHA) to Treat Medial Compartment Knee Osteoarthritis. 2025 review article summarizing available evidence, including reported improvements in pain and function and later survivorship data.
- Nowell JA, Flanigan DC. Implantable Shock Absorber: Breakthrough or Hype? Current Reviews in Musculoskeletal Medicine. 2026;19:27.