Knee (stifle joint) Problems

Overview:

A pet's stifle is the joint that connects the upper and lower leg bones—the femur and the tibia.  In people it is considered the knee.  While there are numerous conditions that can effect the knee joint, the most common are:

Cranial Cruciate Ligament Rupture: The cranial cruciate ligament is an extremely important stabilizer inside your pet's knee.  The ligament can be damaged as a result of injury or degeneration.  Rupture of this ligament either partial or complete, results in joint instability, cartilage damage, inflammation and arthritis. The menisci are the cartilage-like disc that sits between the femur (thigh) and the tibia (shin) bones.  They serve as a shock absorber, position sensor and load bearer within the joint and can be damaged when the cranial cruciate ligament is ruptured.  

Patellar Luxation: The patella (or knee cap) is a small bone that is situated in a groove within the femur (thigh bone) in the knee cap.  This bone helps the knee function, allowing it to flex and extend normally.  Patellar luxation is a condition where the knee cap is dislocated either towards the inside of the limb (medial) or the outside (lateral).  Patellar luxation typically occurs because of malalignment of the muscles and bones of the hind limb.  While this occurs most often in dogs, cats can experience patellar luxation as well.

Osteochondritis Dissecans:  Osteochondrosis is the abnormal development of cartilage at the end of the bone. This condition is most often seen in young medium to large-breed dogs. With normal activity, cracks may occur in the diseased cartilage resulting in the formation of a flap and exposure of the underlying bone to the joint environment. 

Signs and Symptoms:

Cranial Cruciate Ligament: Some of the common signs and symptoms associated with a rupture of the cranial cruciate ligament include any combination of:

  • trouble rising from a sitting position
  • pain and stiffness
  • difficulty jumping on furniture or into a car
  • unwillingness to play/decreased activity level
  • limping
  • decreased range of motion
  • popping sound when joint is being used
  • swelling or thickening of the joint, especially on the inside of the shin bone

Patellar Luxation: Symptoms and their severity can vary.  Most pets will suddenly carry the affected limb up for a few steps which may look like they are skipping but then shake or stretch their leg before they regain full use. As the condition progresses, the lameness becomes more frequent and may become continuous.

Osteochondritis Dissecans: Pets with this condition usually begin limping on the affected leg(s).  In many cases, the limping is gradual and improves after rest but becomes more pronounced after exercise.  Although your pet may be limping on one leg, the condition may be present in the other leg as well. In some pets, the affected joint may be swollen and warm to the touch.

Diagnostics:

Cranial Cruciate Ligament: Our specialists typically diagnose complete ruptures of the cranial cruciate ligament with a comprehensive physical examination including palpation, gait observation and X-rays.  Partial ruptures may not result in gross instability of the joint and may have more subtle physical exam and imaging findings.

Patellar Luxation: An orthopedic examination and palpation of an unstable knee is the best way to diagnose this condition.  Additional tests may be needed such as:

  • Palpation under sedation to asses damage to ligaments
  • X-rays
  • CT scans which can help our surgeons plan for surgery if needed

If undiagnosed, this condition can potentially lead to the rupture of the cranial cruciate ligament.

Osteochondritis Dissecans: Diagnosis of OCD requires radiographs or a CT scan to look at the stifle joint. In some cases arthroscopic examination may be needed to confirm a diagnosis.

Treatment:

Cranial Cruciate Ligament: There are surgical and non-surgical treatments for this condition but they depend on your pet's activity level, size, age, skeletal conformation and degree of knee instability.

In general, surgery is the most predictable way to improve the stability of the joint.  Typically, there are two types of surgeries that can address knee instability.

  • Osteotomy-based techniques require a bone cut to change the biomechanics of the knee. These techniques are most commonly recommended for medium to large breed dogs, but can be performed in smaller dogs as well. These techniques predictably result in rapid return to function and an excellent long-term outcome. A number of similar techniques exist and may be discussed during your visit including:  tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA), CORA-based leveling osteotomy (CBLO), and Modified Maquet Procedure (MMP). 
  • Suture-based techniques are divided into two categories. These procedures aim to replace the function of the torn ligament using a prosthetic suture material placed outside the joint, between the femur and tibia.  At VSH, our surgeons perform standard lateral suture repairs,  Tightrope® and bone-anchor stabilization procedures.  These procedures are most often recommended for small to medium dogs though may be performed in larger dogs depending on their specific anatomy.

Non-surgical treatment involves pain medication,  joint supplements, exercise modification, rehab and in some cases braces or orthotics.

Patellar Luxation: For pets with patellar luxations that aren't experiencing symptoms, they many not require surgery.  For those cases that do require surgery, a number of techniques may be required to keep the knee cap in place.

  • Surgery to reconstruct the soft tissue surrounding the knee cap to loosen the side that it has moved towards and tighten the opposite side, placement of sutures to hold the knee and knee cap in place.
  • Surgery to deepen the femoral groove which is where the knee cap sits so that it doesn't slip to either side.
  • Surgery to realign the muscles/bones of the hind limb

Osteochondritis Dissecans: Treatment depends on the severity of the damaged cartilage.  Surgical treatment typically involves removing the cartilage flap from the joint and treatment of the resulting defect to encourage healing.  Alternatively, the defect may be filled with a cartilage transplant or synthetic plug to reconstruct the joint surface.