Knee surgery is necessary when non-surgical treatments, such as physical therapy, medication, or injections, fail to adequately address pain, instability, or loss of function resulting from acute injuries or chronic degenerative conditions. The decision to pursue surgery depends on the specific underlying pathology, the extent of the damage, and the patient’s functional goals. Surgical approaches range from minor “clean-up” procedures to extensive joint reconstruction or complete replacement. Selecting the appropriate technique is a tailored process designed to restore the knee’s mechanics and integrity.
Minimally Invasive Procedures
The least invasive surgical category is arthroscopy, often called “keyhole surgery.” This technique allows a surgeon to operate inside the joint without making a large incision by inserting a small camera (arthroscope) and miniature instruments through two or three small incisions, typically less than a centimeter each. This approach offers reduced recovery time and less soft tissue damage compared to traditional open surgery.
Arthroscopy is frequently used for diagnostic purposes or to address simple mechanical issues. A common procedure is a partial meniscectomy, which involves trimming and removing the damaged section of a torn meniscus. This eliminates the source of mechanical locking or catching within the joint and prevents further irritation.
Another routine arthroscopic intervention is the removal of loose bodies—fragments of bone, cartilage, or other tissue floating within the joint space. These fragments can cause pain, catching, or full locking of the knee, and specialized instruments are used to retrieve them. Surgeons may also perform a synovectomy, which is the removal of inflamed joint lining (synovium) associated with chronic inflammation or certain types of arthritis.
Soft Tissue and Ligament Reconstruction
When the knee’s stability is compromised due to a tear in a major supporting structure, structural rebuilding is required. These surgeries often use arthroscopic access but involve sophisticated techniques to reconstruct the anatomy. The most common procedure is Anterior Cruciate Ligament (ACL) reconstruction, which restores the primary restraint against the tibia sliding forward beneath the femur.
The torn ACL is replaced with a tissue graft. This graft may be an autograft (taken from the patient’s own body, such as the patellar or hamstring tendons) or an allograft (sourced from a deceased donor). The graft is passed through tunnels drilled into the femur and tibia and secured with fixation devices to replicate the native ligament’s function. This procedure stabilizes the joint, preventing long-term damage to the menisci and articular cartilage.
Complex meniscal tears, especially those in the vascularized outer third, require repair through suturing rather than simple trimming. Techniques like all-inside, inside-out, or hybrid methods are used to hold the torn edges together and promote biological healing. Unlike a meniscectomy, meniscal repair preserves the tissue’s natural shock-absorbing function, though it requires a longer, protected recovery period. Reconstruction of the Posterior Cruciate Ligament (PCL), which prevents the tibia from sliding backward, is also performed using similar graft techniques.
Joint Realignment and Cartilage Restoration
These surgeries are typically employed in younger patients or those with localized damage, aiming to preserve the native knee joint. Joint realignment, most commonly performed through an osteotomy, involves cutting and reshaping the bone to shift mechanical load away from a damaged area. For example, a high tibial osteotomy corrects a varus (bow-legged) deformity, shifting weight from the arthritic medial compartment to the healthier lateral compartment.
By correcting the limb’s mechanical axis, an osteotomy can delay the need for a total joint replacement by several years, allowing the patient to remain active. The procedure requires the bone to heal, often involving plates and screws to maintain the corrected angle.
When damage is confined to the articular cartilage, several restoration techniques address the focal defect:
Cartilage Restoration Techniques
- Microfracture is a marrow-stimulation technique where small holes are poked into the exposed subchondral bone, allowing blood and bone marrow cells to form a clot that matures into fibrocartilage.
- Autologous Chondrocyte Implantation (ACI) is a two-stage procedure where healthy cartilage cells are harvested, cultured in a lab to multiply, and then implanted back into the defect during a second operation.
- The Osteochondral Autograft Transfer System (OATS), or mosaicplasty, involves transplanting cylindrical plugs of healthy bone and cartilage from a non-weight-bearing area to fill the focal defect on the weight-bearing surface.
Joint Replacement Surgery
Joint replacement surgery, or arthroplasty, is the definitive solution for end-stage joint disease where irreversible damage causes severe pain and functional limitation. Total Knee Arthroplasty (TKA) is the most common form, involving the removal of damaged bone and cartilage surfaces of the femur, tibia, and often the kneecap (patella). These surfaces are resurfaced with prosthetic components made of metal alloys, such as cobalt chrome or titanium, which articulate against a durable plastic spacer (ultra-high molecular weight polyethylene, or UHMWPE).
Modern TKA implants demonstrate excellent longevity; approximately 82% of total knee replacements are still functioning 25 years after the initial procedure. The plastic spacer has been improved with highly cross-linked polyethylene (HXLPE), which incorporates antioxidants like Vitamin E to reduce wear and extend the implant’s lifespan. TKA is generally indicated for patients with severe osteoarthritis affecting multiple compartments of the knee.
Partial Knee Arthroplasty (PKA), or unicompartmental knee replacement, is a less extensive procedure performed when damage is confined to a single compartment, usually the medial side of the joint. PKA replaces only the damaged surfaces, preserving the healthy cartilage, bone, and surrounding ligaments. This approach offers a smaller incision, faster initial recovery, and preservation of native anatomy. Its long-term survival rate is slightly lower than TKA, with approximately 70% of partial replacements lasting 25 years.