Chondromalacia Patella (Runner’s Knee) What is it and How to Treat It?

runners knee

Chondromalacia patella, often called “runner’s knee” is a condition where the cartilage under the patella breaks down, causing increased knee pain. Whether you’ve personally experienced it or treated patients experiencing it, this type of knee pain is not fun. Unfortunately, the knee is often the victim of your pain, not the cause.

This is often the case with chondromalacia patellae. Lumped together with anterior knee pain or patellofemoral pain syndrome, chondromalacia patellae often affects younger athletes, but you don’t have to be a runner to experience the condition.

Anatomy of The Knee

The knee joint is a hinge-joint filled with cartilage to prevent wear and tear. Composed of tough fibrocartilage, the medial and lateral menisci act like cushions to absorb forces and shock between the tibia and femur.

On the other end of the spectrum, smooth hyaline cartilage behind the patella allows the patella to seamlessly glide in and out of the groove of the femur. However, this hyaline (articular) cartilage can become damaged and soften over time, causing pain. The softening and reduction of hyaline cartilage is the key characteristic of chondromalacia patellae. While chondromalacia patellae is a multifactor condition, there are five main causes:

  1. Limb malalignment – can be caused by several factors
    • Increased femoral anteversion
    • Tibial external rotation
    • Muscle imbalances between quads & hamstrings and/or hip abductors & adductors
  2. Muscle weakness – especially quad weakness
  3. Patella maltracking – due to several potential issues
    • Muscle imbalance between vastus lateralis and vastus medialis (including the vastus medialis oblique – VMO)
    • Chronic lateral subluxation of patella
    • Loss of medial patella movement
    • Lateral patellar tilt around the central ridge of the patella
  4. Overuse – a common culprit in young people
  5. Trauma – often a direct blow to the patella, but can also occur when attempting to twist a bent knee when weight-bearing

Symptoms of Chondromalacia Patella

Symptoms of chondromalacia patella include:

  • Diffuse pain in peripatellar or retropatellar region
  • Insidious onset
  • Vague pain around patella
  • Pain when patella is compressed
  • Increased pain with certain movements like descending stairs, running/walking, kneeling, squatting, and prolonged sitting with the knee bent (sometimes referred to as theater sign)
  • Extreme pain with resisted knee extension exercises

Chondromalacia Patella Diagnosis

Due to the variety of causes of chondromalacia patellae, there’s not a “cookie-cutter” approach to diagnosis. However, viewing the cartilage is typically performed using a T2 MRI. Ruling out bone malalignment and/or fractures is usually done with a CT scan.

Outerbridge Classification System

There are several classification systems used to describe chondral lesions and grade cartilage degeneration. However, while it has limitations, one of most popular systems used to grade cartilage degeneration is the Outerbridge classification system.

  • Grade 0: Normal
  • Grade 1: Cartilage with softening and swelling
  • Grade 2: Fissures that do not reach subchondral bone or exceed 1.5 cm in diameter
  • Grade 3: Fissures on subchondral bone that exceed 1.5 cm in diameter (sometimes referred to as crabmeat appearance)
  • Grade 4: Exposed subchondral bone

While not ideal for prescribing treatment, the Outerbridge classification system can be helpful in determining prognosis and, if necessary, surgical planning.

4 Chondromalacia Patellae Exercises and Stretches

Like I mentioned earlier, chondromalacia patellae has many causes, so each person’s rehab strategy will vary. But in general, exercises targeting the quads (especially the VMO) and hip abductors & adductors are a good place to begin. Here are some exercises and stretches to start with:

  1. Straight Leg Raise: Lie on your back with the injured knee straight and the strong knee bent with your foot planted on the floor. Pointing your toes straight up, slowly raise your leg until it is parallel with your bent knee (about 70 degrees). Hold for a couple of seconds and slowly lower your leg back down (don’t let gravity do all the work though!). Perform 3 sets of 10 to 15 reps, 3-4x per week. Once this exercise becomes easy, you can add ankle weights to increase the intensity.
  2. Modified Straight Leg Raise: Similarly with the Straight Leg Raise, lie on your back with you injured knee straight and the strong knee bent. Point your toes straight up and rotate your leg with the injured knee outward, so your toes are now pointing out. Slowly raise your leg until it is parallel with your bent knee (about 70 degrees). Hold for a couple of seconds and slowly lower your leg back down (don’t let gravity do all the work though!). Perform 3 sets of 10 to 15 reps, 3-4x per week, adding ankle weights later to increase the intensity.
  3. Side Lying Hip Abduction: Lie on your side in a straight line with your legs stacked on top of each other. Your injured leg should be on top. Slowly lift your top leg straight into the air (about 45 degrees), don’t let your pelvis roll forward or backward. Hold for a couple of seconds and release, bringing your leg back to the ground. Perform 3 sets of 10 to 15 reps, 3-4x per week. Add ankle weights if desired.
  4. Side Lying Hip Adduction: Like with the Side Lying Hip Abduction exercise, start on your side with your legs in a straight line, but have the injured leg on the bottom. The other leg can be bent in front of the body or behind, whatever is most comfortable. Lift the bottom leg straight into the air (this isn’t a big motion – expect leg to lift about 1 foot). Like before, make sure to keep your pelvis straight and don’t let it roll forward or backward. Hold for a few seconds and release, slowly bringing your leg back down. Perform 3 sets of 10 to 15 reps, 3-4x per week. Add ankle weights if desired.

A physical therapist can outline additional rehab strategies best suited to your needs. While there is no cure for chondromalacia patellae, with patience and adequate therapy, the pain can be managed, and you can quickly get back to the activities you love!

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This article was written by Gabrielle Kremers, a current DPT student at the University of Central Arkansas who plans to specialize in outpatient sports and orthopedics upon graduating. In her free time, she enjoys a good game of ultimate frisbee, playing board games, and finding ways to be eco-friendly. 


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