Loose Bodies in the Knee

A knee that locks suddenly, will not straighten for a moment, and then releases and feels normal again is describing something moving inside the joint. Loose bodies are fragments of cartilage or bone that have separated and now travel through the joint space, and they are one of the few knee problems where the symptom pattern is close to diagnostic on its own.

Steven Struhl, MD has performed more than 5,000 arthroscopic procedures since entering practice in 1991. He is board certified in orthopedic surgery and separately in sports medicine and arthroscopic surgery, is a member of the Arthroscopy Association of North America, and serves on the faculty of NYU School of Medicine. Loose body removal is among the more satisfying arthroscopic procedures, because the mechanical symptom it causes disappears the day it is taken out.

Loose Body Symptoms in the Knee

• Locking: the knee catching in a position and refusing to move until it is worked free.
• Catching: a momentary snag during motion, less dramatic than true locking.
• Intermittent Symptoms: the fragment moving, so symptoms come and go unpredictably.
• Swelling After Activity: the joint lining irritated by a fragment moving against it.
• A Sensation of Something Moving: patients frequently describe feeling it, and are frequently correct.
• Giving Way: the knee buckling when a fragment lodges between the joint surfaces.

The intermittent nature is the feature that distinguishes this. A knee that locks on Tuesday, behaves perfectly on Wednesday, and locks again on Friday is describing something that moves.

What Causes Loose Bodies

• Osteochondritis Dissecans: a segment of bone and cartilage separating from the joint surface, most common in adolescents.
• Articular Cartilage Injury: a fragment shearing off after trauma or twisting.
• Osteoarthritis: degenerative debris and osteophyte fragments breaking away in an advanced joint.
• Fracture: a knee fracture involving the joint surface leaving fragments within the joint.
• Meniscus Fragments: a torn piece separating and behaving as a loose body.
• Synovial Chondromatosis: an uncommon condition in which the joint lining forms multiple cartilage bodies.

Diagnosing Loose Bodies

Examination during a locked episode is definitive and it is also uncommon, since most patients arrive between episodes with a knee that examines normally. That is why the history carries so much weight here. Radiographs show fragments that contain bone and will miss fragments that are purely cartilage, which is a meaningful limitation, since many loose bodies are cartilage alone. MRI identifies cartilaginous fragments and, importantly, identifies where they came from, since the defect left behind may need treatment in its own right. CT is used occasionally when precise bony detail is needed for planning.

Arthroscopic Loose Body Removal

Removal is done arthroscopically as an outpatient procedure through two small incisions.

• Systematic Inspection: the entire joint is examined, since fragments migrate and there is frequently more than one.
• Fragment Retrieval: the loose body is grasped and withdrawn, sometimes needing to be reduced in size first.
• Source Assessment: the defect the fragment came from is evaluated and treated where appropriate.
• Fragment Fixation: in selected cases, particularly younger patients with a large osteochondral fragment, the piece is reattached rather than removed.

That last option is worth understanding. In a young patient with a substantial fragment of bone and cartilage, fixing it back into its bed preserves joint surface that would otherwise be lost, and it is a better long term answer than removal when the fragment is suitable.

Loose Body Removal Recovery Time

Recovery is quick when the removal is the only procedure performed. Weight bearing begins immediately, motion returns within days, and most patients are walking comfortably within a week and back to full activity within four to six weeks. When the underlying defect also needs cartilage treatment, the recovery follows that procedure’s timeline instead, which is considerably longer and involves protected weight bearing.

Schedule a Knee Arthroscopy Consultation in New York City

A knee that locks intermittently is worth evaluating rather than working around, since a fragment moving through the joint damages the cartilage it passes across. Dr. Struhl performs knee arthroscopy at his Manhattan and White Plains offices. Contact our office to schedule an appointment.