Meniscus Repair and Cartilage Restoration in the Knee

Meniscus repair has replaced removal as the standard aim of knee arthroscopy, because the meniscus is the knee's main shock absorber and losing it leads to early arthritis. Surgeons now repair bucket handle tears, reattach torn roots, search for hidden ramp lesions and transplant a donor meniscus, while cartilage defects are treated by size with microfracture, OATS or chondrocyte implantation.

Dr. Vipin Maheshwari, Sr. Consultant - Orthopaedics, Artemis Hospitals, Gurugram, India, put the principle bluntly: a patient can do well without an ACL, but without a meniscus arthritis cannot be stopped. This article covers the shift from excision to preservation of the meniscus, the repair techniques he uses, meniscal transplant, and the ladder of cartilage restoration from microfracture to tissue engineering. The complete guide to knee and shoulder arthroscopy gives the wider picture, and the ACL reconstruction article covers the ligament injuries that so often accompany meniscal tears.

Meniscus repair versus removal: why the meniscus must be preserved

The meniscus is a C-shaped wedge of fibrocartilage between the thigh bone (femur) and the shin bone (tibia), one on the inner side of the knee and one on the outer. Every step, turn and jump passes through it. It spreads load across the joint so that the cartilage of the femur does not transmit stress directly onto the cartilage of the tibia.

When Dr. Maheshwari trained, a torn meniscus was simply cut out. The patient's pain went, and both patient and surgeon were satisfied. What that approach ignored was the hoop stress: the circumferential tension the intact meniscus carries as it is compressed, which is how it absorbs load. Remove it, and nothing remains between the bones. Femoral cartilage rubs directly on tibial cartilage, wears away, and the patient develops arthritis years earlier than he otherwise would. Hence his rule: whenever possible, preserve the meniscus, and never cut it if it can be saved.

The field has moved through four stages: excision, repair to restore hoop function, preservation, and now replacement of a meniscus lost in earlier surgery, with regeneration using orthobiologics for small tears.

Which meniscus tears heal: the blood supply zones

The meniscus is not a very vascular structure, and its blood supply runs from the outside in. Surgeons divide it into three zones:

• Red-red zone: the outer rim near the joint capsule. It has a decent blood supply, which is why peripheral tears heal better.
• Red-white zone: the middle third, where the blood supply is moderate. Dr. Maheshwari still attempts repair here, but the repair must be augmented.
• White-white zone: the inner edge, where the blood supply is extremely poor and tears do not heal well.

Tears between the zones, such as radial tears, also heal quite well in his experience.

Meniscus repair techniques

Dr. Maheshwari chooses the technique to suit the tear, and is explicit that the method matters less than the result: whichever implant is used and whichever way it is passed, the anatomy and biomechanics must be right. The main options are:

• All-inside repair, in which devices pass and anchor sutures entirely from within the joint.
• Inside-out repair, in which sutures are passed from inside the joint and tied over the capsule through a small incision.
• Outside-in repair, in which sutures are passed from outside the joint inwards.
• Hybrid repair, combining these on a single tear.

A blood clot placed at the repair site is an established way to augment meniscal repair, because the cells it carries help the tissue regenerate.

A large bucket handle tear

A bucket handle tear is a long tear in which the inner part of the meniscus flips into the centre of the joint like the handle of a bucket. Dr. Maheshwari showed a large medial meniscus tear, about a month old, running from the body of the meniscus to the posterior horn. It was repaired with multiple sutures, combining all-inside and inside-out techniques, restoring the meniscus to near-normal. Patients repaired this way tend to do very well, even in sport. Removing such a meniscus is not harmless, he warned.

Meniscal root repair

A root tear detaches the meniscus from its anchoring point on the tibia, so it can no longer resist hoop stress. In a patient around 50 years old with some arthritis in the joint, Dr. Maheshwari performed a transtibial root repair: a tunnel was drilled through the tibia, sutures were passed through the meniscal root, pulled down the tunnel and fixed over a button on the front of the shin. After the repair the meniscus sat back in place, and the probe could no longer displace it into the posterior gutter. An anchor-based repair is the alternative. A root repair, he said, can give a knee years. He performs it even in 70-year-olds whose anatomy is suitable, or combines it with a high tibial osteotomy, a realignment of the shin bone that offloads the damaged side of the knee.

Ramp lesions: the hidden meniscal tear

A ramp lesion is a tear at the junction of the back of the medial meniscus and the joint capsule. It is easily missed from the standard front portals. A surgeon may scope the whole knee, find nothing obvious, wash out and leave, while the cause of the pain remains.

Dr. Maheshwari's answer is routine. In all arthroscopies he makes a posteromedial portal, an extra entry point at the back of the inner knee, to view the meniscus from behind, or uses a 70-degree scope from the front to inspect the posterior horn and root. Identifying and treating the lesion matters more than the repair technique chosen. Missed meniscal tears, including root tears and ramp lesions, are in his view the most common cause of pain after ACL reconstruction.

Meniscal transplant

A meniscal transplant replaces a meniscus that has been lost, typically removed in earlier surgery or after a bucket handle tear went untreated for months and was excised. It suits a young, high-demand patient whose cartilage is still preserved.

Dr. Maheshwari's technique uses a meniscus from a young donor, implanted arthroscopically:

1. The anterior and posterior roots are repaired to their attachments.
2. Multiple sutures anchor the body of the meniscus to the capsule.
3. The site is prepared by rasping, and platelet-rich plasma (PRP), a platelet concentrate from the patient's blood, and bone marrow aspirate concentrate (BMAC) are added.
4. The graft is expected to heal into place over time.

The rationale is long-term. Nobody wants a patient who has a complete meniscectomy at 20 to return at 25 or 30 with arthritis and no good options left.

Cartilage restoration: matching the procedure to the defect

Every knee operation, in Dr. Maheshwari's framing, is ultimately done to protect cartilage for the future. Without cartilage the knee will not function, whatever else has been fixed. Articular cartilage, the smooth surface covering the bone ends, has little capacity to heal on its own, so treatment has evolved from repair to regeneration and now to tissue engineering. The procedure is chosen by the size of the defect.

Microfracture for small defects

Microfracture involves making small holes through the base of a cartilage defect into the bone beneath. With the tourniquet applied, the surgeon continues until fat droplets are seen oozing from the marrow. The marrow contents form a clot from which fibrocartilage develops. It is not the original cartilage, but it gives the knee good stability and protects the surrounding cartilage. Dr. Maheshwari limits microfracture to small defects of no more than about 4 to 6 mm; beyond 6 mm he moves to a cartilage transplant. Published guidance sizes defects by area rather than diameter: microfracture is generally used for defects under about 2 to 3 cm², osteochondral autograft transfer for about 1 to 4 cm², and chondrocyte implantation for larger lesions.

OATS: osteochondral autograft transfer

OATS moves a cylinder of cartilage, with its underlying bone, from a non-weight-bearing area of the patient's own knee into the defect. Dr. Maheshwari usually harvests from the anterolateral aspect of the femur. The steps are to measure the defect, prepare a socket, harvest a matching plug and press it in. It can be done arthroscopically or open, in a single stage.

He considers it one of the best methods of recreating both cartilage and its bony bed, and suited to defects of around 6 to 10 mm. The grafts tend to heal well in six to eight weeks. Some patients report pain at the donor site, which he finds very rare. Graft size is the limitation: about 20 mm is the most he would take, which is nonetheless a useful size for the medial femoral condyle. In one case he showed, a defect on the lateral femoral condyle had lost both cartilage and bone; a 10 mm socket was prepared and filled with a plug harvested from the anterolateral femur.

Autologous chondrocyte implantation for large defects

Sometimes a large cartilage defect is an unwelcome discovery during ACL surgery, with loose cartilage floating in the joint. Where the defect is large, involves both the medial and lateral sides, or is too big for an OATS graft, Dr. Maheshwari turns to autologous chondrocyte implantation (ACI):

1. Harvest: cartilage is shaved from the edge of the defect or from the anterolateral femur and collected in a filter device.
2. Culture: the cells are mixed with BMAC or PRP and sent to a laboratory, where they are grown over about six weeks.
3. Implantation: the patient returns after about six weeks and the cultured cells are implanted into the defect.

In his account, ACI regenerates the patient's own type of cartilage rather than fibrocartilage; studies describe the repair tissue as hyaline-like. The drawback is two operations. For a large defect, he considers it a valuable option.

Scaffolds and single-stage alternatives

Because patients do not want two operations, single-stage alternatives are emerging. Synthetic collagen scaffolds, osteochondral scaffolds derived from allograft and other materials can be placed into large defects. A defect found incidentally during surgery can be covered with a scaffold fixed in place with fibrin glue, on which fibrocartilage forms.

Tissue engineering

The next frontier, for cartilage as for the meniscus, is tissue engineered in the laboratory for use as a graft. Dr. Maheshwari noted that it is not yet freely available in India and expects that to change soon.

Orthobiologics for small meniscal tears and cartilage defects

For small meniscal tears and small cartilage defects that are only mildly symptomatic, in low-demand patients who are not interested in surgery, Dr. Maheshwari offers orthobiologics such as PRP and BMAC without an operation, and reports that patients do symptomatically very well. A course of PRP needs three to four injections at least two weeks apart. The complete guide discusses who suits this route, and its cost.

Meniscus repair success rate and cost

Dr. Maheshwari put the success rate of meniscal repair at about 90 to 95%, even where a long-standing tear must be trimmed and the remnant repaired; results depend on how much of the meniscus is torn and how early the patient presents. Published series report that around one repair in four to five fails within five years, with better results for peripheral tears and when the repair accompanies an ACL reconstruction. He gave approximate all-inclusive costs at Artemis Hospitals of USD 2,500 to 3,000 for meniscal debridement and USD 4,000 to 5,000 for meniscal repair, depending on the number of anchors used. Benchmarks for other arthroscopic procedures are on the orthopaedic treatment cost page. The meniscal questions doctors raised in the session, on healing zones and on why modern practice preserves tissue, are answered in the Live Discussion. Where a knee is already beyond preservation, Dr. Rohit Lamba's article on knee arthritis and complex replacement covers the next step.