Specialty
Three different anterior knee problems with overlapping symptoms and very different treatments. Sub-specialty evaluation by Dr. Sabrina Strickland at the Hospital for Special Surgery in New York.
Three distinct conditions are often grouped together as "anterior knee pain." Chondromalacia is softening and early breakdown of the cartilage on the back of the kneecap or front of the trochlea, visible on MRI. Anterior knee arthritis is end-stage cartilage loss in the patellofemoral compartment, visible on x-ray. Patellar tendinopathy ("jumper's knee") is degeneration of the patellar tendon itself — pain is on the tendon, not behind the kneecap. The three look similar to patients but require very different treatment plans: structured PT and selective cartilage care for chondromalacia and anterior arthritis; eccentric loading rehabilitation as the foundation for patellar tendinopathy; and cartilage restoration (MACI, OATS, osteochondral allograft) when there is a focal full-thickness defect that warrants resurfacing. Dr. Sabrina Strickland evaluates these patients at the Hospital for Special Surgery in New York and matches treatment to the actual driver of pain.
Anterior knee pain is one of the most common reasons patients are referred to a knee specialist. It is also one of the most often mislabeled. "Knee pain" gets called "chondromalacia" in some offices, "patellar tendonitis" in others, and "arthritis" in a third — sometimes for the same patient with the same MRI. The right treatment depends on which of the three is actually driving the pain, and they require fundamentally different protocols. This page covers what each condition is, how to tell them apart, the non-surgical care that actually works for each, when surgery is appropriate, and what surgical options exist.
For closely related topics, see patellar pain and patellofemoral arthritis for the full anterior knee pain workup; knee arthritis for OA, RA, and post-traumatic arthritis throughout the knee; MACI cartilage repair and cartilage transplantation (OATS & allograft) for cartilage-restoration options; and joint preservation and osteotomy for realignment when patellar maltracking contributes.
Softening or early breakdown of cartilage on the back of the kneecap or front of the trochlea. Visible on MRI. Pain is deep, retropatellar, worse with stairs, sitting, squatting. Cartilage damage on a spectrum from softening (Grade 1) to full-thickness loss (Grade 4).
End-stage cartilage loss in the patellofemoral compartment. Visible on x-ray as joint-space narrowing, osteophytes, and bony changes. Long-standing course, progressive over years. Often follows years of patellar maltracking, prior dislocations, or chondromalacia.
Degeneration of the patellar tendon, usually at the lower pole of the kneecap. Pain is on the tendon itself, worse with jumping and explosive activity ("jumper's knee"). Common in volleyball, basketball, soccer, dance, and explosive lifting.
The most common diagnostic error is conflating the three. A patient with deep retropatellar pain and a healthy patellar tendon does not have tendonitis. A patient with localized lower-pole tenderness and a normal cartilage MRI does not have chondromalacia. Getting the diagnosis right is the first step toward effective treatment.
Chondromalacia patellae is softening, fissuring, or breakdown of the cartilage on the back of the kneecap (and sometimes the front of the trochlea). It is graded:
Chondromalacia pain is typically deep and retropatellar — "behind the kneecap" rather than "on the kneecap" or "below the kneecap." It is often worse with activities that load the patellofemoral joint: descending stairs, squatting, prolonged sitting (the "theater sign"), and kneeling. Crepitus is common but not diagnostic.
Many cases of chondromalacia respond well to non-surgical care: structured PT focused on quadriceps and hip stabilizer strengthening, activity modification toward lower-load options during flares, NSAIDs, and selective injection therapy. Cartilage restoration is reserved for focal full-thickness defects (Grade 4 in a defined area) in patients whose function or sport requires it — not for diffuse softening.
Anterior knee arthritis — isolated patellofemoral arthritis — is end-stage cartilage loss limited to the kneecap and trochlea. The medial and lateral compartments of the knee may still be healthy. Patients typically present in their 40s, 50s, or 60s with a long history of anterior knee pain that has progressed over years.
The distinguishing features:
Treatment includes the same non-surgical foundation (PT, weight management, NSAIDs, selective injections) but with a different surgical endpoint: when isolated and end-stage, anterior knee arthritis can be treated with patellofemoral arthroplasty — a partial knee replacement that resurfaces only the kneecap and trochlea, preserving the medial and lateral compartments and the cruciate ligaments. For full detail on patellofemoral arthroplasty, see patellar pain and patellofemoral arthritis.
Patellar tendinopathy — commonly but inaccurately called "patellar tendonitis" — is degeneration of the patellar tendon, typically at the lower pole of the kneecap. It is a load-management failure: tendon load has exceeded the tendon's recovery capacity for long enough that the tendon structure itself has changed, with disorganized collagen, neovascularization, and altered biomechanics. The "-itis" suffix is misleading because the dominant pathology is degeneration, not inflammation.
Distinguishing features:
Treatment is fundamentally different from cartilage-driven anterior knee pain. The foundation of patellar tendinopathy care is eccentric loading rehabilitation — a structured progressive loading program that remodels the degenerative tendon over weeks to months. NSAIDs and rest are not the answer; the tendon needs progressive load to heal. PRP injection is an option for refractory cases. Surgery is rare and reserved for tendons that fail comprehensive non-surgical management.
The diagnosis is built from history, physical exam, and targeted imaging.
Pain location ("behind the kneecap" vs. "on the kneecap" vs. "below the kneecap"), activity triggers (stairs vs. jumping vs. running), prior knee injuries or surgeries, prior patellar dislocations, sport and training history, and what has and has not been tried. The pain pattern alone often points strongly to one of the three.
Because the three conditions are different, non-surgical care looks different for each.
Cycling, swimming, elliptical, and walking on level ground typically load the patellofemoral joint less than running, stair climbing, or deep squatting. The goal is to break the inflammatory cycle, not to stop exercising.
Quadriceps and VMO strengthening in pain-free range, hip abductor and external rotator strengthening, posterior chain (glute and hamstring) work, core control, and proprioception. Stretching of the iliotibial band, quadriceps, and calves.
NSAIDs for short-course inflammatory control. Cortisone for flares or end-stage disease. Hyaluronic acid (viscosupplementation) for arthritic pain in selected patients. PRP for joint-preservation candidates seeking biologic options.
Reduce or stop the explosive loading (jumping, sprint starts, deep squatting) that is driving symptoms. This is not "no exercise" — it is "no exercise that flares."
The foundation of tendinopathy care. A structured progressive loading program (decline single-leg squat protocols, heavy slow resistance) that remodels the degenerative tendon over weeks to months. Counter-intuitive but well-evidenced.
Platelet-rich plasma injection into the affected portion of the tendon is a reasonable option for tendons that have not responded to a comprehensive eccentric loading program. Evidence is strongest in chronic tendinopathy that has failed conservative care.
Reserved for tendons that fail comprehensive non-surgical management. Procedures include debridement of the degenerate portion of the tendon, sometimes with adjunctive tenodesis or repair.
| Procedure | Best for | What it does | Recovery |
|---|---|---|---|
| Knee arthroscopy | Loose cartilage flap, mechanical catching, loose body | Minimally invasive removal or fixation of a discrete mechanical problem | 4–8 weeks |
| MACI cartilage repair | Focal full-thickness cartilage defect (2–10 cm²) on the patella or trochlea | Two-stage cartilage repair using your own cultured cells. Full procedure walk-through → | 9–18 months |
| Osteochondral autograft (OATS) | Smaller focal defects (1–4 cm²), particularly in younger patients | Plug of cartilage and bone moved from a non-weight-bearing area to the defect | 6–9 months |
| Osteochondral allograft | Larger defects with bone involvement | Donor cartilage and bone plug. More on cartilage transplantation → | 9–12 months |
| Tibial tubercle osteotomy | Cartilage damage in the setting of patellar maltracking | Cuts and repositions the tibial tubercle to offload the worn facet. More on osteotomies → | 4–6 months |
| MPFL reconstruction | Cartilage damage from prior patellar dislocations | Restores the medial soft-tissue restraint to prevent further dislocation that would damage the cartilage repair. Full procedure walk-through → | 4–6 months |
| Patellar tendon debridement | Refractory patellar tendinopathy that has failed all non-surgical care | Removes the degenerate portion of the tendon | 4–6 months |
| Patellofemoral arthroplasty | End-stage isolated anterior knee arthritis with normal medial/lateral compartments | Partial knee replacement of the kneecap and trochlea only | 3–6 months |
Younger patients with anterior knee cartilage loss are particularly good candidates for joint-preserving procedures rather than replacement. The goal in this population is to preserve the native joint, delay or avoid replacement, and protect the cartilage that remains. Options include:
A sub-specialty second opinion is particularly worth seeking when:
All three cause anterior knee pain but they are different problems. Chondromalacia is softening or early breakdown of the cartilage on the back of the kneecap or front of the trochlea — visible on MRI as cartilage signal change. Anterior knee arthritis is end-stage cartilage loss in the patellofemoral compartment — visible on x-ray as joint-space narrowing. Patellar tendonitis (more accurately patellar tendinopathy) is degeneration and inflammation of the patellar tendon, usually at the lower pole of the kneecap — pain is on the tendon itself, not behind the kneecap.
Cartilage damage does not heal in any clinically meaningful way — adult cartilage has very limited capacity for repair. What can improve is the symptom picture: structured PT, activity modification, NSAIDs, and selective injections often produce meaningful symptom relief that allows patients to function well even though the underlying cartilage damage remains. For focal full-thickness defects, cartilage restoration procedures (MACI, OATS, osteochondral allograft) can resurface the damaged area.
High-load deep squats, jumping, downhill running, and high-volume running may aggravate symptoms during a flare. Most patients do better with low-impact options (cycling, swimming, elliptical) during the active phase, then gradually return to running with strength and form work in place. Running itself does not necessarily accelerate cartilage damage in well-aligned knees with appropriate load progression — but symptoms guide the protocol.
Diagnosis is based on history and physical exam, often supported by standing weight-bearing x-rays to assess alignment and joint-space loss, and by MRI to grade the cartilage. Cartilage damage is graded from softening (Grade 1) to fissuring (Grade 2) to deep partial-thickness loss (Grade 3) to full-thickness loss with exposed bone (Grade 4).
Patellar tendinopathy ("jumper's knee") is degeneration of the patellar tendon, usually at the lower pole of the kneecap. The pain is on the tendon itself, worse with jumping and explosive activity. Treatment is fundamentally different from cartilage-driven kneecap pain: eccentric loading rehabilitation is the foundation of care, not anti-inflammatory medication, and PRP can be considered for refractory cases.
Arthroscopy can remove loose cartilage flaps, fix unstable cartilage fragments, and address mechanical symptoms. For focal full-thickness cartilage defects, cartilage restoration options include MACI (matrix-induced autologous chondrocyte implantation), osteochondral autograft transfer (OATS), and osteochondral allograft transplantation. When patellar maltracking is the underlying driver of cartilage damage, MPFL reconstruction or tibial tubercle osteotomy may be combined with the cartilage repair.
Arthroscopic debridement and loose-body removal typically require 4 to 8 weeks of recovery. Cartilage restoration surgery (MACI, OATS, allograft) requires 6 to 12 months for return to most activity, and 12 to 18 months for return to high-impact sport — the biology of cartilage maturation drives the timeline. Combined cases with osteotomy or MPFL reconstruction sit in between.
Younger patients with cartilage loss are particularly good candidates for joint-preserving procedures rather than replacement. Options include cartilage restoration (MACI, OATS, osteochondral allograft), realignment osteotomy when malalignment is contributing, MPFL reconstruction when prior dislocations have damaged the cartilage, and the MISHA implantable shock absorber for patients with concurrent medial compartment wear. The goal is to preserve the native joint and delay or avoid replacement.
For the full anterior knee pain workup, see patellar pain and patellofemoral arthritis. For OA, RA, and post-traumatic arthritis throughout the knee, see knee arthritis. For cartilage-restoration options, see MACI cartilage repair and cartilage transplantation (OATS & allograft). For realignment osteotomy when patellar maltracking is contributing, see joint preservation and osteotomy. If your kneecap also slips out of place, see patellar instability and MPFL reconstruction surgery.
If you have been given conflicting diagnoses for your anterior knee pain, or you have a focal cartilage defect on MRI and want to understand cartilage-restoration candidacy, bring your imaging to a sub-specialty consultation.
Enter your question below and a representative will get right back to you.