Knee Cartilage Injury & Repair in Bethlehem & the Lehigh Valley
Articular cartilage is the smooth, glassy tissue that caps the ends of the bones inside your knee and lets the joint glide with very little friction. When a discrete area of that surface is damaged — by a twisting injury, a direct blow, a patellar dislocation, or a condition such as osteochondritis dissecans — the result is a focal cartilage defect: a pothole in an otherwise healthy joint surface. Dr. Michael Hendel, MD, PhD evaluates and treats knee cartilage injuries for patients across Bethlehem, Allentown, Easton, and the greater Lehigh Valley from his office at St. Luke's Orthopedic Care in Bethlehem.
Cartilage problems often announce themselves with activity-related pain, recurrent swelling after exercise, or mechanical symptoms such as catching or locking. Because these symptoms overlap with meniscus tears and other knee conditions, an examination and imaging — typically standing X-rays and MRI — are needed to establish the diagnosis and measure the size and depth of the defect.
Why Cartilage Doesn’t Heal on Its Own
Unlike skin, muscle, or bone, articular cartilage has no blood supply, no nerves, and very few cells capable of mounting a repair response. When a full-thickness defect occurs, the body cannot deliver the healing cells and growth factors that repair other tissues. At best, the body may fill a defect with fibrocartilage — a scar-like tissue that is mechanically inferior to native cartilage and tends to wear over time.
Left untreated, a symptomatic full-thickness defect can enlarge and expose more bone, and the edges of the surrounding cartilage can break down. This is one reason focal defects in younger, active patients deserve a careful evaluation: the goal of restoration is to relieve symptoms now and, where possible, to protect the joint surface over the long term.
Who Is a Candidate for Cartilage Restoration?
Cartilage restoration is not for every knee. It is designed for focal defects in otherwise healthy joints — not for widespread arthritis. Factors Dr. Hendel weighs when deciding whether restoration is appropriate, and which technique to use, include:
- Defect size, depth, and location — small contained defects and large or bone-involving defects call for different techniques
- The rest of the joint — restoration is unlikely to succeed in a knee with diffuse cartilage wear on both sides of the joint
- Limb alignment — a bowed or knock-kneed limb overloads the restored area; an alignment-correcting osteotomy is sometimes recommended alongside restoration
- Ligament stability and meniscus status — an unstable ACL or a deficient meniscus must be addressed for a cartilage procedure to hold up
- Age, body weight, and activity goals — younger, active patients with focal disease tend to be the best candidates
- Willingness to complete a long rehabilitation — cartilage procedures demand months of protected recovery
Many patients with cartilage lesions do not need surgery at all. Activity modification, strengthening, weight management, and injections are reasonable first steps for lesions that are small or minimally symptomatic, and Dr. Hendel discusses these options before any operation is considered.
Cartilage Restoration Techniques
Microfracture — and Its Limits
Microfracture is a marrow-stimulation technique: small perforations are made in the bone at the base of the defect so marrow cells can form a clot that matures into repair tissue. It is arthroscopic, adds little surgical time, and can relieve symptoms for small defects. Its important limitation is that the repair tissue is fibrocartilage, not true articular cartilage — it is less durable, and results tend to decline with larger defects, higher-demand patients, and longer follow-up. For these reasons, microfracture is now generally reserved for small lesions in selected patients, and other techniques are preferred for larger or higher-demand situations.
Osteochondral Autograft Transfer (OATS)
In osteochondral autograft transfer, one or more plugs of the patient’s own bone and cartilage are moved from a lesser-weight-bearing area of the knee into the defect. Because the plug carries living articular cartilage on a bone base, it restores a true hyaline surface and heals bone-to-bone. It is best suited to small and medium defects, since the amount of donor tissue that can be borrowed from the same knee is limited.
Osteochondral Allograft Transplantation
For larger defects, or defects that involve the underlying bone, a size-matched donor osteochondral allograft can resurface the area with mature cartilage and bone in a single procedure, without borrowing from the patient’s own knee. Allograft transplantation is a well-established option for large lesions and for revision of prior cartilage procedures.
MACI (Matrix-Induced Autologous Chondrocyte Implantation)
MACI is a two-stage, cell-based procedure. First, a small sample of the patient’s own cartilage cells is taken arthroscopically. The cells are grown in a laboratory and seeded onto a collagen membrane. In a second operation, the membrane is implanted into the prepared defect, where the cells produce new cartilage tissue. MACI is FDA-approved for symptomatic full-thickness cartilage defects of the knee in adults and is particularly useful for larger defects with intact underlying bone, including defects behind the kneecap.
Realistic Recovery Expectations
Cartilage restoration asks more patience of patients than most knee procedures, because the new tissue needs time to mature before it can accept full load. While every protocol is individualized, a typical arc looks like this:
- Weeks 0–6: protected weight-bearing on crutches for most weight-bearing defects; early motion, often with a continuous passive motion machine after cell-based procedures
- Weeks 6–12: progression to full weight-bearing, restoration of motion, and beginning strengthening
- Months 3–6: progressive strengthening, cycling, and low-impact conditioning
- Months 6–12 and beyond: gradual return to impact activity and sport, guided by strength testing and the specific procedure performed — cell-based repairs generally mature more slowly than bone-based grafts
Dr. Hendel sets these expectations before surgery, because the decision to undergo cartilage restoration should be made with a clear picture of the recovery it requires. Patients who play cutting or contact sports can also review his sports medicine practice for how return-to-play decisions are made.